CA1062266A - Process for the production of 2-aryl-2h-benzotriazoles - Google Patents
Process for the production of 2-aryl-2h-benzotriazolesInfo
- Publication number
- CA1062266A CA1062266A CA240,240A CA240240A CA1062266A CA 1062266 A CA1062266 A CA 1062266A CA 240240 A CA240240 A CA 240240A CA 1062266 A CA1062266 A CA 1062266A
- Authority
- CA
- Canada
- Prior art keywords
- carbon atoms
- nitroazobenzene
- tert
- hydrogen
- chlorine
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D249/00—Heterocyclic compounds containing five-membered rings having three nitrogen atoms as the only ring hetero atoms
- C07D249/16—Heterocyclic compounds containing five-membered rings having three nitrogen atoms as the only ring hetero atoms condensed with carbocyclic rings or ring systems
- C07D249/18—Benzotriazoles
- C07D249/20—Benzotriazoles with aryl radicals directly attached in position 2
Abstract
PROCESS FOR THE PRODUCTION OF
Abstract of the Disclosure An improved process for the production of 2-aryl-2H-benzotriazoles by the reduction of o-nitroazobenzene intermediates with zinc in alkaline medium comprises em-ploying a ratio of moles of alkali to moles of o-nitroazo-benzene intermediate in the range of 0.2-1.7/1 in the presence of less than 150 ppm of iron based on zinc used.
The improved process results in higher yields of high purity products with a concomitant reduction in the amount of undesired cleavage amine by-products and a reduction in effluent pollution problems. The process is carried out in a polar/non-polar solvent mixture.
Abstract of the Disclosure An improved process for the production of 2-aryl-2H-benzotriazoles by the reduction of o-nitroazobenzene intermediates with zinc in alkaline medium comprises em-ploying a ratio of moles of alkali to moles of o-nitroazo-benzene intermediate in the range of 0.2-1.7/1 in the presence of less than 150 ppm of iron based on zinc used.
The improved process results in higher yields of high purity products with a concomitant reduction in the amount of undesired cleavage amine by-products and a reduction in effluent pollution problems. The process is carried out in a polar/non-polar solvent mixture.
Description
This invention pertains to a prc_ess for the preparation of 2-aryl-2H-benzotriazo'es and derivatives thereof. More particularly, the invention relates to an improved process for preparing 2-aryl-2H-benzotriazoles whereby high yields of the desired products are obtained and effluent pollution problems occurring with present processes for making such products are greatly reduced.
The known chemical and electrolytic reduction processes for preparing 2-aryl-benzotriazoles are not practical or economically attractive in many cases. The widely used zinc dust and sodium hydroxide system can produce effluent pollution problems in respect to waste disposal of zinc sludge which is of increasing environ-mental concern.
''' It is therefore an ob~ect of this invention to provide an improved process for the preparation of 2-aryl-:,~
2H-benzotriazoles mitigating severe pollution and environ-mental problems.
~' A further object of this invention is to prepare
The known chemical and electrolytic reduction processes for preparing 2-aryl-benzotriazoles are not practical or economically attractive in many cases. The widely used zinc dust and sodium hydroxide system can produce effluent pollution problems in respect to waste disposal of zinc sludge which is of increasing environ-mental concern.
''' It is therefore an ob~ect of this invention to provide an improved process for the preparation of 2-aryl-:,~
2H-benzotriazoles mitigating severe pollution and environ-mental problems.
~' A further object of this invention is to prepare
2-aryl-2H-benzotriazoles by reduciny and cyclizing the cor-responding o-nitroazobenzene under certain conditions here-~ inafter set forth in greater detail whereby high yields of - the products can be obtained in acceptable purity.
. .: .
,~. ~ ~
-' '~
~ - 2-. .
::' , .
- :
' :. ' . '~, -.
The 2-aryl-2H-benzotriazoles have found wide use as dyestuff intermediates, optical brightener blue fluo-rescent agents and selective ultraviolet light absorbing stabilizers affording valuable protection for fibers, films and a variety of polymeric structures subject to deterioration by ultraviolet radiation. These materials have become important items of commerce.
.
The 2-aryl-2H-benzotriazoles are complex organic molecules which require careful synthetic procedures for their production in good yield and purity.
These materials can be prepared by a variety of methods, but most conveniently by either Process I, the oxidation of o-aminoazobenzene intermediates, or Process II, the reduction of o-nitroazobenzene intermediates.
Process I:
The oxidation of o-aminoazobenzene intermediates proceeds schematically as seen in Equation A
, oxidi~ing ~ \
.2 ~ ~ / ~ ~A~
where oxidizing agents;such;as sodium hypochlorite!,sam-moniacal copper sulfate, air in aqueous or aqueouY-., .: ~ -. ~ , . . ... .
: . :.. ~ , : -, - . -. . ~ .. :~ . .
:-~ ,'........ ' ' ' ` , '.` . - ` -, ' - .
', " ' ' ~: - ' pyridine solution, hydrogen peroxide, hexa~alent chromium compounds, potassium permanganate and the like may be used.
This process is described in U.S. Patent Numbers 2,362,988, 2,784,183, 3,055,896 and 3,072,585.
Process II:
The reduction of o-nitroazobenzene intermediates proceeds schematically as seen in Equation B where a variety of reducing agents ~ ~ reducing ~ N
may be employed as seen from the teachings of U.S. Patent Number 2,362,988. These include alkali sulfides, zinc and ammionia at 80-100C, sodium hydrosulfide, zinc and hydro-chloric acid and ammonium sulfide. The use of ammonium sulfide was also reported by S. N. Chakrabarty et al, J. -Indian Chem. Soc., 5, 55 (1928); CA, 23, 836 (1929) with mixed results depending on the presence or absence of substituent groups on the:2-aryl group. In some cases the desired 2-ary1-2H-benzotriazole was not formed at all ~ith-therproduct of~.the?reductionSbeing on~y~ani~aromatlc :
i¢; amine.
ij , ., .
- .
- - ,-.
.. ~ . . .. . , ... : .. .. ...
Electrolytic reduction of o-nitroazobenzene intermediates was reported by H. Itomi, Mem_Coll. Sci.
Kyoto Imp. Univ., 12A, No. 6, 343 (1929); CA, 24, 2060 (1930) with the use o~ a copper cathode in dilute sodium hydroxide solution. Yields varied from 25 to 60~ depend-ing on specific embodiments and conditions, but with a major impurity being formed, namely the corresponding o-~minoazobenzene by-product.
Tne use of zinc dust and sodium hydroxide as the reducing system for the o-nitroazobenzene intermediates was reported by K. Elbs et al, J. Prakt Chem., 108, 209 (1924); CA, 19, 514 (1925). The yields reported varied from 30 to 85~ depending on the specific o-nitroazobenzene intermediates involved.
,' U.S. Patent Numbers 3,055,896 and 3,072,585 also teach the use of zinc dust and sodium hydroxide as the re-, ducing system for o-nitroazobenzene intermediates. In ';hese cases large molar ratios of sodium hydroxide to the o-nitroazobenzene intermediates (6-20 to 1) are taught.
The yield and purity of products are not taught, but further recrystallization is indicated as necessary to obtain pro-` ducts of good purity.
`, U.S.'Patents 3 r230 ~194 . and 3,77'3,'751 also"teach the use of large malar ratios of sodium hydroxide to the , i-- 5 - . ~
. . . ..
, .
- - . .-.: - . s: - ~. - . -:
o-nitroazobenzene intermediate namely 6.7 to 1 and 4.4 to 1 respectively. Recrystallization is indicated as necessary to obtain a pure product.
:`
Details of the Disclosure .
This invention relates to an improved process for the preparation of 2-aryl-2H-benzotriazoles by the reduction of o-nitroazobenzene intermediates with zinc in alkaline medium wherein the improvement comprises employing a ratio of moles of alkali to moles of o-nitroazobenzene inter-mediate in the range of 0.2~G.84~/i for one type of o-nitro-.. _. "
azobenzene and in the range of 1.2-1.7/1 for a second type of o-nitroazobenzene in the presence of a total amount of ~J iron impurities in the reaction system of less than 150 ppm based on zinc used.
The improved process results in higher yields up to 86% of high purity 2-aryl-2H-benzo-triazole ~, product as a first crop with high yields (up to 4%) of a second crop material of quality only slightly less pure than the first crop. There is a concomitant reduction in the amount or undesired cleavage amine by-products. The latter represents both an economic penalty in manufacture of the desired ~2-aryl-ZH-benzotriazole products ana~a source of effluent poIlution pro~lems. Much less;acid is needea to remove the amine by-products ~from-the~2-ary~
.
. ,.- .. . . . , .. ,. , ~.
2H-benzotriazole products in the improved process reducing the volume and severity of the effluent problem involved.
More specifically, the instant invention provides an improved process for production of 2-aryl-2H-ber.zotriazole compounds having the formula I
.
OH R
R2 N ~ ~R4 . wherein ., .
.. Rl i~ hydrogen or chlorine, .
R2 is hydrogen, chlorine, lower alkyl of 1 to 4 ~ .
carbon atoms, lower alkoxy of 1 to 4 carbon atoms, alkoxy-carb-onyl of 2 to 9 carbon atoms, carboxy or -SO3H, R3 is alkyl of 1 to 12 carbon atoms, alXoxy of 1 to 4 carbon atoms, phenyl, phenyl substituted with alkyl groups, said alkyl groups having 1 to 8 carbon atoms, cyclo-alkyl of 5 to 6 carbon atoms, alkoxy-carbonyl of 2 to 9 carbon atoms, chlorine, carboxyethyl or arylalkyl of 7 to 9 carbon ~atoms, ~_ 7 _ .
. - . .,. . - .... ,, -.
10f~2266 R4 is hydrogen, lower alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 8 carbon atoms, chlorine or hydroxyl, and R5 is hydrogen, alkyl of 1 to 12 carbon atoms, chlorine, cycloalkyl of 5 to 6 carbon atoms or arylalkyl of 7 to 9 carbon atoms.
R2 can be lower alkyl of i to 4 carbon atoms such as methyl, ethyl or n-butyl. R2 can also be lower alkoxy of 1 to 4 carbon atoms such as methoxy, ethoxy or n-butoxy. R2 can also be carboalkoxy of 2 to 9 carbon atoms such as methoxy-carbonyl, ethoxy-carbonyl or n-octoxy-carbonyl.
R3 can be alkyl of 1 to 12 carbon atoms such as methyl, ethyl, sec-butyl, tart-butyl, amyl, tert-octyl or n-dodecyl. R3 can also be alkoxy of 1 to 4 carbon atoms such as methoxy, ethoxy or n-butoxy. R3 is also phenyl substituted with alkyl groups, said alkyl groups having 1 to 8 carbon atoms such as methyl, tert-butyl, tert-amyl or tert-octyl. R3 can also be cycloalkyl of 5 to 6 carbon atoms suc~ as cyclopentyl or cyclohexyl. R3 is also car-boalkoxy of 2 to 9 carbon atoms such as methoxy-carbonyl, ethoxy-carbonyl, n-butoxy-carbonyl or n-octoxy-carbonyl. R3 is also arylalkyl of 7 to 9 carbon atoms such as benzyl, a-methyl-: .: ~ -,, 10~i2Z66 benzyl or ~,-dLmethylbenzyl.
R4 can be lower alkyl of 1 to 4 carbon atoms such as methyl, ethyl or n-butyl.
R4 can also be alkoxy of 1 to 8 carbon atoms such as methoxy, ethoxy, n-butoxy or octoxy.
R5 can be lower alkyl of 1 to 12 carbon atoms such as methyl, sec-butyl. tert-butyl, tert-amyl, tert-octyl, or n-dodecyl.
R5 can also be cycloalkyl or 5 to 6 carbon atoms such as cyclopentyl or cyclohexyl. Rs is also arylalkyl of 7 to 9 carbon atoms such as benzyl, a-me~hylbenzyl or a,a-dimethylbenzyl.
Preferably Rl is hydrogen.
Preferably R2 is hydrogen, chlorine, lower alkyl of 1 to 2 carbon atoms, methoxy or carboxy.
Preferably R3 is alkyl of 1 to 8 carbon atoms cyclohexyl, phenyl, chlorine, a-methylbenzyl or carboxyethyl.
Preferably R4 is hydrogen, hydroxyl, methyl or alkoxy of 1 to 8 carbon atoms.
, . . ~ ,....
- . -10622~6i Preferably R5 is hydrogen, chlorine, alkyl of 1 to 8 carbon atoms,cyclohexyl, benzyl or ~-methylbenzyl.
Most preferably R2 is hydrogen or chlorine.
Most preferably R3 is methyl, tert-butyl, tert-amyl, tert-octyl, sec-butyl~ cyclohexyl, chlorine or carboxyethyl.
Most preferably R4 is hydrogen.
Most preferably R5 is hydrogen, chlorine, methyl, sec-butyl, tert-butyl, tert-amyl, tert-octyl or~ -methylbenzyl.
The improved process involves the reduction of the corresponding o-nitroazobenzene intermediate of the formula II
0~1 R~ R3 11 wherein Rl, R2, R3, R4 and R5 are described previously, with zinc in an aqueous alkali metal hydroxide medium wherein the improvement comprises employing a ratio of moles of alkali to moles of o-nitroazobenzene intermediate in the range of 0.2-1.7/1 in the presence of an amount of the iron impurities in the reaction system of less than 150 ppm based on zinc used.
The o-nitroazobenzene intermediates of formula II useful in this improved process fall into two general types, Type 1 and Type 2.
.... . ... .. . . . .
, - : :: : -':~ , :
' , ' ~062266 In Type 1, R5 cannot be hydrogen and there must be a substituent in the position ortho to the hydroxy group.
In Type 2, R5 must be hydrogen and the hydroxy group must not have a substituent in the ortho position thereto.
The Type 1 o-nitroazobenzene intermediates normally do not form soluble alkali metal phenolate salts, especially when the R5 group is a large hydrocarbon residue. For apparent steric and possibly other unknown reasons, the hydroxy group appears to be inaccessible to or relatively unreactive with the aqueous alkali, thus making e~en a low molar amount of alkali available for producing the reducing couple with zinc.
The Type 2 o-nitroazobenzene intermediates, however, do form soluble or insoluble alkali metal pheno-late salts requiring one mole of alkali per mole of hydroxy group (or o-nitroazobenzene intermediate) in the process.
Thus, the classification of the intermediates of formula II into Type 1 or 2 depends not on solubility of the phenolate salt, but rather on the presence or absence of substitution ortho to the hydroxyl group.
The reasons for the striking differences in the alkali requirement for the successful reduction of an o-nitroazobenzene intermediate of Type 1 compared to one -. .; . ~ , . . . " ~ , . . :. .. ..
,, ,. ,. - .. ,- . . , - . - ~ .. .. ... .
lOf~Z2~;~
of Type 2 are not clearly understood. With Type 1 inter-mediates, a molar ratio of alkali to o-nitroazobenzene intermediate in the range of 0.2-0.848/1 is needed. With l`ype 2 intermediates, a molar ratio of alkali to o-nitro-azobenzene intermediate in the range of 1.2-1.7/1 is re-quired.
In the absence of ortho substitution to the hydroxyl group of Type 2 intermediates, apparently 1 mole of alkali per mole of intermediate is required to form the phenolate salt and then an additional 0.2 mole/mole of intermediate is needed to produce a reducing couple with zinc.
The use of molar ratios of Zn to o-nitroazobenzene of at least 3:1 is preferred.
It is contemplated that with zinc in sodium hydroxide solution two different reducing couples can exist as seen in v. R. Scholder et al, Z. Anorg Allg.
Chem., 241, 76 (1939) as 1. Zn ~ 3(0H) ~ Zn(OH)3 + 2e 2. Zn + 4(OH) ~ Zn(OH)4 + 2e-The improved process using low concentrations of alkalicorresponds to the first couple which appears to be a less powerful, milder, apparently more specific reducing system.
. .
,, . ~ ~ ' ~ ' ' , ' - ~ . . .
-, ~ ' . .
- , 106ZZt;6 It is further contemplated that with the Type 1 intermediates less alkali can react with the hydroxyl group present for steric and related considerations thus requiring less total alkali to produce the mild reducing couple described above.
In the case of the Type 2 intermediates, one mole of alkali is consumed by reaction with the hydroxyl group present. Only an additional 0.2 moles of alkali is then needed to produce the mild reducing couple de-scribed above.
With the o-nitroazobenzene intermediates of Type l, the improved process invol~es the cyclic reduc-tion of the o-nitroazobenzene intermediate of formula II wherein R5 is alkyl of 1 to 12 carbon atoms, chlorine, cycloalkyl of 5 to 6 carbon atoms or arylalkyl of 7 to 9 carbon atoms with zinc in an aqueous alkali metal hydroxide ~;
medium wherein the improvement comprises employing a ratio of moles of alkali to moles of o-nitroazobenzene inter-mediate in the range of 0.2-0.848/1~ preferably 0.3-0.7/1, most preferably 0.3-0.6/1, in the presence of a total amount of the iron impurities in the reaction system of less than 150 ppm based on zinc used, preferably of less than 100 ppm and most preferably of less than 50 ppm.
With Type l intermediates, preferably R5 is chlorine, alkyl of 1 to 8 carbon atoms, cyclohexyl, benzyl or ;, -.. . ~ , - . ,. . , - .
a-methylbenzyl and most preferably R5 is chlorine, methyl, sec-butyl, tert-butyl, tert-amyl, tert-octyl and a-methyl-benzyl.
With the o-nitroazobenzene intermediates of Type 2, the improved process involves the cyclic reduc-tion of the o-nitroazobenzene intermediate of formula II
wherein R5 is hydrogen with zinc in an aqueous alkali metal hydroxlde medium wherein the improvement comprises employing a ratio of moles of alkali to moles of o-nitro-azobenzene intermediate in the range of 1.2 to 1.7~1, prefer-ably 1.2 to 1.4/1, most preferably 1.2 to 1.3/1, in the presence of a total amount of iron impurities in the re-action system of less than 150 ppm based on zinc used, preferably of less than 100 ppm and most preferably of less than 50 ppm.
The definitions of Rl, R , R and R are as previously set forth and are the same for both Type 1 and Type 2 o-nitroazobenzene intermediates.
The starting o-nitroazobenzene intermediates are prepared by coupling the appropriate o-nitrobenzenedia-zonium compounds of formula III
.:
,, . , . . -, .
. , . ' ' ~ -- : , - -.- .' ~ ' ' ' :
1 ~ N=N X
I O ¦ III
2 ~ NO2 wherein Rl and R2 are as described previously and X is chloride, sulfate, or other anionic species, but prefer-ably chloride, with phenols of formula IV
OH
~ R5 IV
which couple in the ortho position to the hydroxy group.
. _ . ,, _ The o-nitrobenzenediazonium compounds are .n turn prepared by standard diazotization procedures using sodium nitrite in acid solution with the corresponding o-nitro-anilines of formula V
R~H2 V
..
- . . . .
-For illustration purposes some specific examples of compounds of formulas IV and V are listed. These items are generally available as items of commerce.
Compounds of Formula rv p-cresol 2,4-di-tert-butylphenol 2,4-di-tert-amylphenol 2,4-di-tert-octylphenol 2-tert-butyl-4-methylphenol 4-cyclohexylphenol 4-tert-butylphenol 4-tert-amylphenol 4-tert-octylphenol 2,4-dimethylphenol
. .: .
,~. ~ ~
-' '~
~ - 2-. .
::' , .
- :
' :. ' . '~, -.
The 2-aryl-2H-benzotriazoles have found wide use as dyestuff intermediates, optical brightener blue fluo-rescent agents and selective ultraviolet light absorbing stabilizers affording valuable protection for fibers, films and a variety of polymeric structures subject to deterioration by ultraviolet radiation. These materials have become important items of commerce.
.
The 2-aryl-2H-benzotriazoles are complex organic molecules which require careful synthetic procedures for their production in good yield and purity.
These materials can be prepared by a variety of methods, but most conveniently by either Process I, the oxidation of o-aminoazobenzene intermediates, or Process II, the reduction of o-nitroazobenzene intermediates.
Process I:
The oxidation of o-aminoazobenzene intermediates proceeds schematically as seen in Equation A
, oxidi~ing ~ \
.2 ~ ~ / ~ ~A~
where oxidizing agents;such;as sodium hypochlorite!,sam-moniacal copper sulfate, air in aqueous or aqueouY-., .: ~ -. ~ , . . ... .
: . :.. ~ , : -, - . -. . ~ .. :~ . .
:-~ ,'........ ' ' ' ` , '.` . - ` -, ' - .
', " ' ' ~: - ' pyridine solution, hydrogen peroxide, hexa~alent chromium compounds, potassium permanganate and the like may be used.
This process is described in U.S. Patent Numbers 2,362,988, 2,784,183, 3,055,896 and 3,072,585.
Process II:
The reduction of o-nitroazobenzene intermediates proceeds schematically as seen in Equation B where a variety of reducing agents ~ ~ reducing ~ N
may be employed as seen from the teachings of U.S. Patent Number 2,362,988. These include alkali sulfides, zinc and ammionia at 80-100C, sodium hydrosulfide, zinc and hydro-chloric acid and ammonium sulfide. The use of ammonium sulfide was also reported by S. N. Chakrabarty et al, J. -Indian Chem. Soc., 5, 55 (1928); CA, 23, 836 (1929) with mixed results depending on the presence or absence of substituent groups on the:2-aryl group. In some cases the desired 2-ary1-2H-benzotriazole was not formed at all ~ith-therproduct of~.the?reductionSbeing on~y~ani~aromatlc :
i¢; amine.
ij , ., .
- .
- - ,-.
.. ~ . . .. . , ... : .. .. ...
Electrolytic reduction of o-nitroazobenzene intermediates was reported by H. Itomi, Mem_Coll. Sci.
Kyoto Imp. Univ., 12A, No. 6, 343 (1929); CA, 24, 2060 (1930) with the use o~ a copper cathode in dilute sodium hydroxide solution. Yields varied from 25 to 60~ depend-ing on specific embodiments and conditions, but with a major impurity being formed, namely the corresponding o-~minoazobenzene by-product.
Tne use of zinc dust and sodium hydroxide as the reducing system for the o-nitroazobenzene intermediates was reported by K. Elbs et al, J. Prakt Chem., 108, 209 (1924); CA, 19, 514 (1925). The yields reported varied from 30 to 85~ depending on the specific o-nitroazobenzene intermediates involved.
,' U.S. Patent Numbers 3,055,896 and 3,072,585 also teach the use of zinc dust and sodium hydroxide as the re-, ducing system for o-nitroazobenzene intermediates. In ';hese cases large molar ratios of sodium hydroxide to the o-nitroazobenzene intermediates (6-20 to 1) are taught.
The yield and purity of products are not taught, but further recrystallization is indicated as necessary to obtain pro-` ducts of good purity.
`, U.S.'Patents 3 r230 ~194 . and 3,77'3,'751 also"teach the use of large malar ratios of sodium hydroxide to the , i-- 5 - . ~
. . . ..
, .
- - . .-.: - . s: - ~. - . -:
o-nitroazobenzene intermediate namely 6.7 to 1 and 4.4 to 1 respectively. Recrystallization is indicated as necessary to obtain a pure product.
:`
Details of the Disclosure .
This invention relates to an improved process for the preparation of 2-aryl-2H-benzotriazoles by the reduction of o-nitroazobenzene intermediates with zinc in alkaline medium wherein the improvement comprises employing a ratio of moles of alkali to moles of o-nitroazobenzene inter-mediate in the range of 0.2~G.84~/i for one type of o-nitro-.. _. "
azobenzene and in the range of 1.2-1.7/1 for a second type of o-nitroazobenzene in the presence of a total amount of ~J iron impurities in the reaction system of less than 150 ppm based on zinc used.
The improved process results in higher yields up to 86% of high purity 2-aryl-2H-benzo-triazole ~, product as a first crop with high yields (up to 4%) of a second crop material of quality only slightly less pure than the first crop. There is a concomitant reduction in the amount or undesired cleavage amine by-products. The latter represents both an economic penalty in manufacture of the desired ~2-aryl-ZH-benzotriazole products ana~a source of effluent poIlution pro~lems. Much less;acid is needea to remove the amine by-products ~from-the~2-ary~
.
. ,.- .. . . . , .. ,. , ~.
2H-benzotriazole products in the improved process reducing the volume and severity of the effluent problem involved.
More specifically, the instant invention provides an improved process for production of 2-aryl-2H-ber.zotriazole compounds having the formula I
.
OH R
R2 N ~ ~R4 . wherein ., .
.. Rl i~ hydrogen or chlorine, .
R2 is hydrogen, chlorine, lower alkyl of 1 to 4 ~ .
carbon atoms, lower alkoxy of 1 to 4 carbon atoms, alkoxy-carb-onyl of 2 to 9 carbon atoms, carboxy or -SO3H, R3 is alkyl of 1 to 12 carbon atoms, alXoxy of 1 to 4 carbon atoms, phenyl, phenyl substituted with alkyl groups, said alkyl groups having 1 to 8 carbon atoms, cyclo-alkyl of 5 to 6 carbon atoms, alkoxy-carbonyl of 2 to 9 carbon atoms, chlorine, carboxyethyl or arylalkyl of 7 to 9 carbon ~atoms, ~_ 7 _ .
. - . .,. . - .... ,, -.
10f~2266 R4 is hydrogen, lower alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 8 carbon atoms, chlorine or hydroxyl, and R5 is hydrogen, alkyl of 1 to 12 carbon atoms, chlorine, cycloalkyl of 5 to 6 carbon atoms or arylalkyl of 7 to 9 carbon atoms.
R2 can be lower alkyl of i to 4 carbon atoms such as methyl, ethyl or n-butyl. R2 can also be lower alkoxy of 1 to 4 carbon atoms such as methoxy, ethoxy or n-butoxy. R2 can also be carboalkoxy of 2 to 9 carbon atoms such as methoxy-carbonyl, ethoxy-carbonyl or n-octoxy-carbonyl.
R3 can be alkyl of 1 to 12 carbon atoms such as methyl, ethyl, sec-butyl, tart-butyl, amyl, tert-octyl or n-dodecyl. R3 can also be alkoxy of 1 to 4 carbon atoms such as methoxy, ethoxy or n-butoxy. R3 is also phenyl substituted with alkyl groups, said alkyl groups having 1 to 8 carbon atoms such as methyl, tert-butyl, tert-amyl or tert-octyl. R3 can also be cycloalkyl of 5 to 6 carbon atoms suc~ as cyclopentyl or cyclohexyl. R3 is also car-boalkoxy of 2 to 9 carbon atoms such as methoxy-carbonyl, ethoxy-carbonyl, n-butoxy-carbonyl or n-octoxy-carbonyl. R3 is also arylalkyl of 7 to 9 carbon atoms such as benzyl, a-methyl-: .: ~ -,, 10~i2Z66 benzyl or ~,-dLmethylbenzyl.
R4 can be lower alkyl of 1 to 4 carbon atoms such as methyl, ethyl or n-butyl.
R4 can also be alkoxy of 1 to 8 carbon atoms such as methoxy, ethoxy, n-butoxy or octoxy.
R5 can be lower alkyl of 1 to 12 carbon atoms such as methyl, sec-butyl. tert-butyl, tert-amyl, tert-octyl, or n-dodecyl.
R5 can also be cycloalkyl or 5 to 6 carbon atoms such as cyclopentyl or cyclohexyl. Rs is also arylalkyl of 7 to 9 carbon atoms such as benzyl, a-me~hylbenzyl or a,a-dimethylbenzyl.
Preferably Rl is hydrogen.
Preferably R2 is hydrogen, chlorine, lower alkyl of 1 to 2 carbon atoms, methoxy or carboxy.
Preferably R3 is alkyl of 1 to 8 carbon atoms cyclohexyl, phenyl, chlorine, a-methylbenzyl or carboxyethyl.
Preferably R4 is hydrogen, hydroxyl, methyl or alkoxy of 1 to 8 carbon atoms.
, . . ~ ,....
- . -10622~6i Preferably R5 is hydrogen, chlorine, alkyl of 1 to 8 carbon atoms,cyclohexyl, benzyl or ~-methylbenzyl.
Most preferably R2 is hydrogen or chlorine.
Most preferably R3 is methyl, tert-butyl, tert-amyl, tert-octyl, sec-butyl~ cyclohexyl, chlorine or carboxyethyl.
Most preferably R4 is hydrogen.
Most preferably R5 is hydrogen, chlorine, methyl, sec-butyl, tert-butyl, tert-amyl, tert-octyl or~ -methylbenzyl.
The improved process involves the reduction of the corresponding o-nitroazobenzene intermediate of the formula II
0~1 R~ R3 11 wherein Rl, R2, R3, R4 and R5 are described previously, with zinc in an aqueous alkali metal hydroxide medium wherein the improvement comprises employing a ratio of moles of alkali to moles of o-nitroazobenzene intermediate in the range of 0.2-1.7/1 in the presence of an amount of the iron impurities in the reaction system of less than 150 ppm based on zinc used.
The o-nitroazobenzene intermediates of formula II useful in this improved process fall into two general types, Type 1 and Type 2.
.... . ... .. . . . .
, - : :: : -':~ , :
' , ' ~062266 In Type 1, R5 cannot be hydrogen and there must be a substituent in the position ortho to the hydroxy group.
In Type 2, R5 must be hydrogen and the hydroxy group must not have a substituent in the ortho position thereto.
The Type 1 o-nitroazobenzene intermediates normally do not form soluble alkali metal phenolate salts, especially when the R5 group is a large hydrocarbon residue. For apparent steric and possibly other unknown reasons, the hydroxy group appears to be inaccessible to or relatively unreactive with the aqueous alkali, thus making e~en a low molar amount of alkali available for producing the reducing couple with zinc.
The Type 2 o-nitroazobenzene intermediates, however, do form soluble or insoluble alkali metal pheno-late salts requiring one mole of alkali per mole of hydroxy group (or o-nitroazobenzene intermediate) in the process.
Thus, the classification of the intermediates of formula II into Type 1 or 2 depends not on solubility of the phenolate salt, but rather on the presence or absence of substitution ortho to the hydroxyl group.
The reasons for the striking differences in the alkali requirement for the successful reduction of an o-nitroazobenzene intermediate of Type 1 compared to one -. .; . ~ , . . . " ~ , . . :. .. ..
,, ,. ,. - .. ,- . . , - . - ~ .. .. ... .
lOf~Z2~;~
of Type 2 are not clearly understood. With Type 1 inter-mediates, a molar ratio of alkali to o-nitroazobenzene intermediate in the range of 0.2-0.848/1 is needed. With l`ype 2 intermediates, a molar ratio of alkali to o-nitro-azobenzene intermediate in the range of 1.2-1.7/1 is re-quired.
In the absence of ortho substitution to the hydroxyl group of Type 2 intermediates, apparently 1 mole of alkali per mole of intermediate is required to form the phenolate salt and then an additional 0.2 mole/mole of intermediate is needed to produce a reducing couple with zinc.
The use of molar ratios of Zn to o-nitroazobenzene of at least 3:1 is preferred.
It is contemplated that with zinc in sodium hydroxide solution two different reducing couples can exist as seen in v. R. Scholder et al, Z. Anorg Allg.
Chem., 241, 76 (1939) as 1. Zn ~ 3(0H) ~ Zn(OH)3 + 2e 2. Zn + 4(OH) ~ Zn(OH)4 + 2e-The improved process using low concentrations of alkalicorresponds to the first couple which appears to be a less powerful, milder, apparently more specific reducing system.
. .
,, . ~ ~ ' ~ ' ' , ' - ~ . . .
-, ~ ' . .
- , 106ZZt;6 It is further contemplated that with the Type 1 intermediates less alkali can react with the hydroxyl group present for steric and related considerations thus requiring less total alkali to produce the mild reducing couple described above.
In the case of the Type 2 intermediates, one mole of alkali is consumed by reaction with the hydroxyl group present. Only an additional 0.2 moles of alkali is then needed to produce the mild reducing couple de-scribed above.
With the o-nitroazobenzene intermediates of Type l, the improved process invol~es the cyclic reduc-tion of the o-nitroazobenzene intermediate of formula II wherein R5 is alkyl of 1 to 12 carbon atoms, chlorine, cycloalkyl of 5 to 6 carbon atoms or arylalkyl of 7 to 9 carbon atoms with zinc in an aqueous alkali metal hydroxide ~;
medium wherein the improvement comprises employing a ratio of moles of alkali to moles of o-nitroazobenzene inter-mediate in the range of 0.2-0.848/1~ preferably 0.3-0.7/1, most preferably 0.3-0.6/1, in the presence of a total amount of the iron impurities in the reaction system of less than 150 ppm based on zinc used, preferably of less than 100 ppm and most preferably of less than 50 ppm.
With Type l intermediates, preferably R5 is chlorine, alkyl of 1 to 8 carbon atoms, cyclohexyl, benzyl or ;, -.. . ~ , - . ,. . , - .
a-methylbenzyl and most preferably R5 is chlorine, methyl, sec-butyl, tert-butyl, tert-amyl, tert-octyl and a-methyl-benzyl.
With the o-nitroazobenzene intermediates of Type 2, the improved process involves the cyclic reduc-tion of the o-nitroazobenzene intermediate of formula II
wherein R5 is hydrogen with zinc in an aqueous alkali metal hydroxlde medium wherein the improvement comprises employing a ratio of moles of alkali to moles of o-nitro-azobenzene intermediate in the range of 1.2 to 1.7~1, prefer-ably 1.2 to 1.4/1, most preferably 1.2 to 1.3/1, in the presence of a total amount of iron impurities in the re-action system of less than 150 ppm based on zinc used, preferably of less than 100 ppm and most preferably of less than 50 ppm.
The definitions of Rl, R , R and R are as previously set forth and are the same for both Type 1 and Type 2 o-nitroazobenzene intermediates.
The starting o-nitroazobenzene intermediates are prepared by coupling the appropriate o-nitrobenzenedia-zonium compounds of formula III
.:
,, . , . . -, .
. , . ' ' ~ -- : , - -.- .' ~ ' ' ' :
1 ~ N=N X
I O ¦ III
2 ~ NO2 wherein Rl and R2 are as described previously and X is chloride, sulfate, or other anionic species, but prefer-ably chloride, with phenols of formula IV
OH
~ R5 IV
which couple in the ortho position to the hydroxy group.
. _ . ,, _ The o-nitrobenzenediazonium compounds are .n turn prepared by standard diazotization procedures using sodium nitrite in acid solution with the corresponding o-nitro-anilines of formula V
R~H2 V
..
- . . . .
-For illustration purposes some specific examples of compounds of formulas IV and V are listed. These items are generally available as items of commerce.
Compounds of Formula rv p-cresol 2,4-di-tert-butylphenol 2,4-di-tert-amylphenol 2,4-di-tert-octylphenol 2-tert-butyl-4-methylphenol 4-cyclohexylphenol 4-tert-butylphenol 4-tert-amylphenol 4-tert-octylphenol 2,4-dimethylphenol
3,4-dimethylphenol
4-chlorophenol 2,4-dichlorophenol 3,4-dichlorophenol 4-phenylphenol .
4-phenoxyphenol 3-octyloxyphenol . . _ . .
4-o-tolylphenol 4-(4'-tert-octyl)phenylphenol ethyl 4-hydroxybenzoate .
, . . . . .
, ~ ' ' ' ' 10622~;6 n-octyl 4-hydroxybenzoate 4-methoxyphenol 4-n-octylphenol 4-n-dodecylphenol resorcinol 4-(~-methylbenzyl)phenol 2-(a-methylbenzyl)-4-methylphenol 2-cyclohexyl-4-methylphenol 4-sec-hutylphenol 2-sec-butyl-4-tert-butylphenol 2-tert-butyl-4-sec-butylphenol 4-carboxyethylphenol 2-methyl 4-carboxyethylphenol Preferably compounds of formula IV useful in this invention are p-cresol 2,4-di-tert-butylphenol 2,4-di-tert-amylphenol :-2,4-di-tert-octylphenol 2-tert-butyl-4-methylphenol 4-tert-octylphenol 4-n-octylphenol 4-n-dodecylphenol resorcinol ",.. ,.. - .- .- . .. , . ~ . . ,; . . . .. -.. ' : . -. ~.
.. -. -: - . . ~ - ---2-sec-butyl-4-tert-butylphenol 2-~a-methylbenzyl)-4-methylphenol 3-octyloxyphenol Cor.;pounds Ol Fo~llula V
o-nitroaniline 4-chloro-2-nitroaniline 4,5-dichloro-2-nitroaniline 4-methoxy-2-nitroaniline 4-methyl-2-nitroaniline 4-ethyl-2-nitroaniline n-butyl 3-nitro-4-aminobenzoate n-octyl 3-nitro-4-aminobenzoate 4-n-butoxy-2-nitroaniline -.
3-nitro-4-aminobenzoic acid ~-3-nitro-4-aminobenzenesulfonic acid Preferably compounds of Formula V useful in this invention are o-nitroaniline 4-chloro-2-nitroaniline The process is carried out in an aqueous/organic solvent medium where the exact choice of organic solvent is determined by the solubility characteristics of the specific o-nitroazobenzene intermediates and 2-aryl-2H-benzotriazole products involved.
,. ,, ,~: : -:' : ' :' In the case of the Type 1 o-nitroazobenzene intermediates, the use of aqueous alkali and the polar/
non-polar solvent mixture, isopropanol mineral spirits, proved beneficial in order to provide the best ambience for the rapid reduction of the o-nitroazobenzene intermediate (Type 1). The use of a single oraanic solvent either isopropanol or mineral spirits alone with aqueous alkali required a much longer reaction time to effect the reduction of the o-nitroazobenzene intermediate to the corresponding 2-aryl-2H-benzotriazole.
The polar materials which may be used in the mixed solvent for the instant process include isopropanol, ethanol, methanol, n-butanol, 2-ethylhexanol and the like. Isopro-panol is preferred. The non-polar materials useful in the mixed solvents are mineral spirits, toluene, benzene, hexane, cyclohexane, xylene, heptane and the like. Amsco mineral spirits are preferred.
The ratio by weight of polar to non-polar materials in the solvent mixture is about 2/1 to 2/3, and preferably 3/2 to 1/l.
In the case of Type 2 o-nitroazobenzene inter-mediates the same solvent mixtures used with the Type l intermediates can be used, but an a~ueous alkali/aromatic solvent mixture proved particularly beneficial in the ~ .
-:"
. . - . - - ~ . .
.-- , . . ,. ,~, .
.. . , . , .. . , .. .. ~ . - . . -.. ..
- - ~: ' ~ ':
- : ,, .
~l062266 instant process with the Type 2 o-nitroazobenzene inter-mediate reductions. The aromatic solvents included benzene, toluene and xylene with toluene being preferred.
The alkaline medium used in this improved process is an aqueous alkali metal hydroxide solution. The alkali metal hydroxides used in this improved process are sodium hydroxide, potassiùm hydroxide and lithium hydroxide. For reasons of economy and availability, sodium hydroxide is preferred.
, . . ...................................... .
Contemplated equivalents for the alkali metal hydroxides include ammonia and the alkaline earth hydrox-ides such as magnesium hydroxide, calcium hydroxide and barium hydroxide.
Although the decrease in molar ratio of alkali to the o-nitroazobenzene intermediates raises the yields of the desired 2-aryl-2H-benzotriazoles significantly, the yields are further enhanced when the total concentration of iron impurities in the reaction system is kept to low levels (under 150 ppm based on zinc used).
It is surprising that the low alkali concentration increases the yield of desired product on the reduction step.
It is also surprising that the decrease of the iron concen-tration further increases the yield of the 2-aryl-2H-benzotriazoles.
.. .. .......
. -. ~
.: . : - - . . .
.. . . : . . .
In Table I are seen the results on yields of the effect of the molar ratio of alkali to o-nitroazobenzene intermediate, (Type 1), at a low and constant concentration of iron impurities, on reaction time re~uired.to achieve complete reduction, the exotherm experienced as 2inc was added all at one time to the system and the amount of undesirable aminophenol cleavage by-product formed.
A comparison with a typical run at a high ratio of alkali to o-nitroazobenzene intermediate (Type 1) is also shown. At ratios above 0.9 moles alkali to 1 mole o-nitroazobenzene intermediate (Type 1), extreme exotherms are noted with each addition of zinc to the system requir-ing expensive brine cooling, rather than simple water :~ -cooling, to keep the reaction temperature within the con-trolled limits (55 to 65C). Reaction times at 65 are not appreciably less than when less alkali is used, but the total yield of desired 2-aryl-2H-benzotriazole is considerably less (71.5% compared to 81.5%, see Example l) and the yield of undesirable cleavage amine by-product is many times as great (11.4% compared to 2-3%, see Example l).
With less undesired by-product, the quality of the desired product is concomitantly better making product isolation and purification by one crystallization and trituration correspondingly simplified.
, ~ ... . . . , ,, , ~
- . .. . . - . , -. : - : :
''~ . ' .
TABLE_I
Effect of Molar Ratio of Alkali to o-Nitroazobenzene Intermediate (Type 1) at Low and Constant Iron Content on Reduction to 2-ArYl-2H-Benzotriazole Mole Alkali 0.212 0.318 0.605 0.848 1.67*
to o-Nitroazobenzene Intermediate (1 mole) Exotherm when small small moderate strong very Zn is added at ca.lC ca.lC ca.7C strong 55C with Air-cooling Hold Time at 7.25 5.25 2.75 1.5 1.5 65C to Complete Reduction (hours) First Crop Yield ~ 79.5 80.4 80.7 76.7 71.5 By-Product Material 3 2-3 5.5 8.5 11.4 Precipitated at pH
4-phenoxyphenol 3-octyloxyphenol . . _ . .
4-o-tolylphenol 4-(4'-tert-octyl)phenylphenol ethyl 4-hydroxybenzoate .
, . . . . .
, ~ ' ' ' ' 10622~;6 n-octyl 4-hydroxybenzoate 4-methoxyphenol 4-n-octylphenol 4-n-dodecylphenol resorcinol 4-(~-methylbenzyl)phenol 2-(a-methylbenzyl)-4-methylphenol 2-cyclohexyl-4-methylphenol 4-sec-hutylphenol 2-sec-butyl-4-tert-butylphenol 2-tert-butyl-4-sec-butylphenol 4-carboxyethylphenol 2-methyl 4-carboxyethylphenol Preferably compounds of formula IV useful in this invention are p-cresol 2,4-di-tert-butylphenol 2,4-di-tert-amylphenol :-2,4-di-tert-octylphenol 2-tert-butyl-4-methylphenol 4-tert-octylphenol 4-n-octylphenol 4-n-dodecylphenol resorcinol ",.. ,.. - .- .- . .. , . ~ . . ,; . . . .. -.. ' : . -. ~.
.. -. -: - . . ~ - ---2-sec-butyl-4-tert-butylphenol 2-~a-methylbenzyl)-4-methylphenol 3-octyloxyphenol Cor.;pounds Ol Fo~llula V
o-nitroaniline 4-chloro-2-nitroaniline 4,5-dichloro-2-nitroaniline 4-methoxy-2-nitroaniline 4-methyl-2-nitroaniline 4-ethyl-2-nitroaniline n-butyl 3-nitro-4-aminobenzoate n-octyl 3-nitro-4-aminobenzoate 4-n-butoxy-2-nitroaniline -.
3-nitro-4-aminobenzoic acid ~-3-nitro-4-aminobenzenesulfonic acid Preferably compounds of Formula V useful in this invention are o-nitroaniline 4-chloro-2-nitroaniline The process is carried out in an aqueous/organic solvent medium where the exact choice of organic solvent is determined by the solubility characteristics of the specific o-nitroazobenzene intermediates and 2-aryl-2H-benzotriazole products involved.
,. ,, ,~: : -:' : ' :' In the case of the Type 1 o-nitroazobenzene intermediates, the use of aqueous alkali and the polar/
non-polar solvent mixture, isopropanol mineral spirits, proved beneficial in order to provide the best ambience for the rapid reduction of the o-nitroazobenzene intermediate (Type 1). The use of a single oraanic solvent either isopropanol or mineral spirits alone with aqueous alkali required a much longer reaction time to effect the reduction of the o-nitroazobenzene intermediate to the corresponding 2-aryl-2H-benzotriazole.
The polar materials which may be used in the mixed solvent for the instant process include isopropanol, ethanol, methanol, n-butanol, 2-ethylhexanol and the like. Isopro-panol is preferred. The non-polar materials useful in the mixed solvents are mineral spirits, toluene, benzene, hexane, cyclohexane, xylene, heptane and the like. Amsco mineral spirits are preferred.
The ratio by weight of polar to non-polar materials in the solvent mixture is about 2/1 to 2/3, and preferably 3/2 to 1/l.
In the case of Type 2 o-nitroazobenzene inter-mediates the same solvent mixtures used with the Type l intermediates can be used, but an a~ueous alkali/aromatic solvent mixture proved particularly beneficial in the ~ .
-:"
. . - . - - ~ . .
.-- , . . ,. ,~, .
.. . , . , .. . , .. .. ~ . - . . -.. ..
- - ~: ' ~ ':
- : ,, .
~l062266 instant process with the Type 2 o-nitroazobenzene inter-mediate reductions. The aromatic solvents included benzene, toluene and xylene with toluene being preferred.
The alkaline medium used in this improved process is an aqueous alkali metal hydroxide solution. The alkali metal hydroxides used in this improved process are sodium hydroxide, potassiùm hydroxide and lithium hydroxide. For reasons of economy and availability, sodium hydroxide is preferred.
, . . ...................................... .
Contemplated equivalents for the alkali metal hydroxides include ammonia and the alkaline earth hydrox-ides such as magnesium hydroxide, calcium hydroxide and barium hydroxide.
Although the decrease in molar ratio of alkali to the o-nitroazobenzene intermediates raises the yields of the desired 2-aryl-2H-benzotriazoles significantly, the yields are further enhanced when the total concentration of iron impurities in the reaction system is kept to low levels (under 150 ppm based on zinc used).
It is surprising that the low alkali concentration increases the yield of desired product on the reduction step.
It is also surprising that the decrease of the iron concen-tration further increases the yield of the 2-aryl-2H-benzotriazoles.
.. .. .......
. -. ~
.: . : - - . . .
.. . . : . . .
In Table I are seen the results on yields of the effect of the molar ratio of alkali to o-nitroazobenzene intermediate, (Type 1), at a low and constant concentration of iron impurities, on reaction time re~uired.to achieve complete reduction, the exotherm experienced as 2inc was added all at one time to the system and the amount of undesirable aminophenol cleavage by-product formed.
A comparison with a typical run at a high ratio of alkali to o-nitroazobenzene intermediate (Type 1) is also shown. At ratios above 0.9 moles alkali to 1 mole o-nitroazobenzene intermediate (Type 1), extreme exotherms are noted with each addition of zinc to the system requir-ing expensive brine cooling, rather than simple water :~ -cooling, to keep the reaction temperature within the con-trolled limits (55 to 65C). Reaction times at 65 are not appreciably less than when less alkali is used, but the total yield of desired 2-aryl-2H-benzotriazole is considerably less (71.5% compared to 81.5%, see Example l) and the yield of undesirable cleavage amine by-product is many times as great (11.4% compared to 2-3%, see Example l).
With less undesired by-product, the quality of the desired product is concomitantly better making product isolation and purification by one crystallization and trituration correspondingly simplified.
, ~ ... . . . , ,, , ~
- . .. . . - . , -. : - : :
''~ . ' .
TABLE_I
Effect of Molar Ratio of Alkali to o-Nitroazobenzene Intermediate (Type 1) at Low and Constant Iron Content on Reduction to 2-ArYl-2H-Benzotriazole Mole Alkali 0.212 0.318 0.605 0.848 1.67*
to o-Nitroazobenzene Intermediate (1 mole) Exotherm when small small moderate strong very Zn is added at ca.lC ca.lC ca.7C strong 55C with Air-cooling Hold Time at 7.25 5.25 2.75 1.5 1.5 65C to Complete Reduction (hours) First Crop Yield ~ 79.5 80.4 80.7 76.7 71.5 By-Product Material 3 2-3 5.5 8.5 11.4 Precipitated at pH
5.5 Calculated as Mole % Aminophenol Hydrochloride *Zinc added portionwise As seen from Table I, the mole ratio of alkali to o-nitroazobenzene intermediate (Type 1) in the improved process can range from about 0.2 to 0.848/1. Preferably the ratio is 0.3 to 0.7/1 in order to optimize time of reaction, product yields and the like, and most preferably the ratio is 0.3 to 0.6/1.
When the mole ratio of alkali to o-nitroazo-benzene intermediate of Type 2 is in the operable range for ....
~r :~ ' ' ' - :: ' .
~062266 the improved process described above for the Type 1 inter-mediates, the desired 2-aryl-2H-benzotriazoles derived from the Type 2 intermediates are not foxmed in acceptable yield and purity.
However, it is seen on Table II, when the moles of sodium hydroxide to moles of o-nitroazobenzene inter-mediate of Type 2 were increased to over 1.2~1, that the reduction to the desired 2-aryl-2H-benzotriazole occured readily, but that the reduction was not totally specific and that the desired product was contaminated with by-products, largely of amine nature.
It is contemplated that the lack of specificity seen in the results on Table II may be related to the con-centration of the o-nitroazobenzene intermediate in the reduction phase. In, the water/isopropanol mineral spirits system employed, it is considered that the reduc-tion phase is the aqueous alXali/isopropanol phase rather than the organic phase Amsco mineral spirits/isopropanol.
..... ~ . .
, , ~
TABLE II
Effect of Molar Ratio of Sodium Hydroxide to o-Nitroazobenzene Intermediate of Type 2 at Low and Constant Iron Content on Reduction to 2-ArYl-2H-Benzctriazole Moles of Sodium Hydroxide to Reaction o-Nitroazobenzene Time in Reaction Results as Intermediate of Hours at Seen by TLC Analysis Run Type 2 (1 mole) 65C of Reaction Mixture*
l 0.42 13 Essentially no reduc-tion, trace of N-oxide seen 2 0.60 5 Essentially no reduc-tion, low concentra-tion of N-oxide seen 3 0.84 5 Mixture of starting --material and N-oxide -4 1.26 5 No starting material or N-oxide present, reduction occurred to desired product plus by-products 1.68 5 No starting material or N-oxide present,.
reduction occurred to desired product plus by-products *Solvent was isopropanol mineral spirits/water.
Accordingly, the isopropanol mineral spirits were replaced by toluene. The reduction occurs in the a~ueous caustic phase and the desired product is concentrat~d in the toluene phase. Additionally, the toluene phase can ,: :
. - - .... .. .. .
be saturated at lower temperatures with premade product al-lowing for an increased recovery of desired product upon final crystallization from the toluene. A convenient method of achieving this is to reuse the mother liquor from a previous run, already saturated with desired product, in a subsequent reduction batch reaction.
On Table III is seen the results of reactions carried out in toluene/aqueous alkali systems, at various ratios of alkali to o-nitroazobenzene intermediates of Type 2. The specificity of the reduction reaction to give the desired 2-aryl-2H-benzotriazole with a mininum of by-products was greatly increased in this aqueous toluene system.
: :,, : -; . .
~06ZZ66 TABLE III
Effect of Molar Ratio of Sodium Hydroxide to o-Nitroazobenzene Intermediate of Type 2 in Toluene/Water at 65C
Moles of Sodium Hydroxide o-Nitroa-benzene Reaction Yield of Product Intermediate Reaction Results In of Type 2 Time in by TLC Mother Run tl mole) Hours Analysis Isolated Liquor Total 1 0.84 16 Mixture product, Not iso- -N-oxide and lated starting mate-rial 2 0.84 20.+ N-oxide, pro- Not iso-8 at 80C duct and by- lated products 3 1.26 7 Trace N-oxide 48.9 39.1 88.0 4 1.26 4 No N-oxide 57.0 29.6 86.6 1.40 4 Trace N-oxide 61.0 17.9 78.9
When the mole ratio of alkali to o-nitroazo-benzene intermediate of Type 2 is in the operable range for ....
~r :~ ' ' ' - :: ' .
~062266 the improved process described above for the Type 1 inter-mediates, the desired 2-aryl-2H-benzotriazoles derived from the Type 2 intermediates are not foxmed in acceptable yield and purity.
However, it is seen on Table II, when the moles of sodium hydroxide to moles of o-nitroazobenzene inter-mediate of Type 2 were increased to over 1.2~1, that the reduction to the desired 2-aryl-2H-benzotriazole occured readily, but that the reduction was not totally specific and that the desired product was contaminated with by-products, largely of amine nature.
It is contemplated that the lack of specificity seen in the results on Table II may be related to the con-centration of the o-nitroazobenzene intermediate in the reduction phase. In, the water/isopropanol mineral spirits system employed, it is considered that the reduc-tion phase is the aqueous alXali/isopropanol phase rather than the organic phase Amsco mineral spirits/isopropanol.
..... ~ . .
, , ~
TABLE II
Effect of Molar Ratio of Sodium Hydroxide to o-Nitroazobenzene Intermediate of Type 2 at Low and Constant Iron Content on Reduction to 2-ArYl-2H-Benzctriazole Moles of Sodium Hydroxide to Reaction o-Nitroazobenzene Time in Reaction Results as Intermediate of Hours at Seen by TLC Analysis Run Type 2 (1 mole) 65C of Reaction Mixture*
l 0.42 13 Essentially no reduc-tion, trace of N-oxide seen 2 0.60 5 Essentially no reduc-tion, low concentra-tion of N-oxide seen 3 0.84 5 Mixture of starting --material and N-oxide -4 1.26 5 No starting material or N-oxide present, reduction occurred to desired product plus by-products 1.68 5 No starting material or N-oxide present,.
reduction occurred to desired product plus by-products *Solvent was isopropanol mineral spirits/water.
Accordingly, the isopropanol mineral spirits were replaced by toluene. The reduction occurs in the a~ueous caustic phase and the desired product is concentrat~d in the toluene phase. Additionally, the toluene phase can ,: :
. - - .... .. .. .
be saturated at lower temperatures with premade product al-lowing for an increased recovery of desired product upon final crystallization from the toluene. A convenient method of achieving this is to reuse the mother liquor from a previous run, already saturated with desired product, in a subsequent reduction batch reaction.
On Table III is seen the results of reactions carried out in toluene/aqueous alkali systems, at various ratios of alkali to o-nitroazobenzene intermediates of Type 2. The specificity of the reduction reaction to give the desired 2-aryl-2H-benzotriazole with a mininum of by-products was greatly increased in this aqueous toluene system.
: :,, : -; . .
~06ZZ66 TABLE III
Effect of Molar Ratio of Sodium Hydroxide to o-Nitroazobenzene Intermediate of Type 2 in Toluene/Water at 65C
Moles of Sodium Hydroxide o-Nitroa-benzene Reaction Yield of Product Intermediate Reaction Results In of Type 2 Time in by TLC Mother Run tl mole) Hours Analysis Isolated Liquor Total 1 0.84 16 Mixture product, Not iso- -N-oxide and lated starting mate-rial 2 0.84 20.+ N-oxide, pro- Not iso-8 at 80C duct and by- lated products 3 1.26 7 Trace N-oxide 48.9 39.1 88.0 4 1.26 4 No N-oxide 57.0 29.6 86.6 1.40 4 Trace N-oxide 61.0 17.9 78.9
6 1.6 4 Trace N-oxide 61.1 20.4 81.5
7 1.26* 3.5 Trace N-oxide 78.4 2.4 80.8
8 3.37* 0.5 No N-oxide 73.3 4.5 77.8 *The solubility of the desired product was decreased in:the toluene when using toluene saturated with premade produ~t thus, increasing significantly the isolated yields~i^n-these runs. ' -~26 -- , . . - , . .
- . . . . : . ~
-~062266 ~ comparison of Run 7 on Table III shows t~at the use of the 1.26 moles of sodium hydroxide to 1 mole of o-nitroazobenzene of Type 2 led to a commercially sig-nificant 5% increase in isolated yield of pure product compared to Run 8 where a high amount of alkali (3.37/1) was used.
In commercial processes, an increase in yield of 5% can be very significant, both in reducing unit costs, reducing effluent and pollution problems as well as after resulting in a purer product since by-product formation is concomitantly depressed.
In the presence of iron, the yields of desired 2-aryl-2H-benzotriazoles fall off even when the molar ratio of alkali to o-nitroazo intermediate is low and the amount of cleavage amine by-products greatly increased. In Table IV, the effect of adding iron as iron oxide ~Fe2O3) even at the parts per million (ppm) levels based on the charge of zinc is seen. The yield of desired products is greatly affected.
At the 210 ppm level, the yield drops nearly 15% to 67.6%
compared to 82.4% control. Addition of more iron impurities produces even more deleterious results with a greatly en-~hanced~yield of~-undesired-by-produ~t~.
.
.
. .
- '' :
-~, TABLE I'~' Effect of Iron Added as Ferric Oxide on Reduction of o-Nitroazobenzene Intermediate (Type 1) at a Constant Ratio of Alkali (0.42 mole) to o-Nitroazobenzene Intermediate (1 mole) ppm Fe on Zn used 2100 700 210 40 none Time Required at * 7.5 5 4-5 3.75 65 for Complete Reduction (hours) First Crop Yield % * 48.6 67.6 80.582.4 By-Product Material -- 31.2 17.0 2.54.7 Precipitated at p~
5.5 Calculated as Mole % Aminophenol Hydrochloride *Reduction was incomplete and the product formed is the N-oxy compound corresponding to the o-nitroazobenzene intermediate.
The addition of iron impurities as ferric chlo-ride as seen on Table V is even more pronounced. Only 80 ppm of iron based on the zinc charged leads to low yields (66.5~) of the desired 2-aryl-2H-benzotriazole pro-duct.
: .
-^28 -.. ~ - . . , , -- .. - . ~
, :. .
.. , , . . .: -~. : ' , :: . :
-- ? ~ --TABLE V
Effect of Iron Added as Ferric Chloride on Reduction o-Nitroazobenzene Intermediate (Type 1) at a Constant Ratio of Alkali (0.42 mole) to o-Nitroazobenzene Intermediate (1 mole) ppm Fe on Zn used 80 130 First Crop 66.5 59.1 Yield %
By-Product Material 18.5 23.1 Precipitated at pH
5.5 Calculated as Mole % Aminophenol Hydrochloride Commercial zinc dust varies widely in the amount of residual iron impurities ranging from under 100 ppm to over 1500 ppm iron. The latter zinc dusts are totally unacceptable for use with this improved process due to their high iron impurity contents. Zinc dust containing 100 ppm or less iron can be used satisfactorily in the improved process. Preferably the iron content in the zinc dust should be less than 80 ppm and most preferably less than 50 ppm.
The physical state of the iron is also apparently critical. The more finely divided ferric oxide resulting from addition of ferric chloride to the alkaline reduction system proved particularly detrimental compared to the ,. , . .... . . ., :
addition of commercial preformed ferric oxide. The use of more finely divided ferric oxide required iron levels in the 50 ppm range or less for satisfactory results.
Iron can also be introduced into the system from sources other than the zinc dust. Another source of iron present during the reduction step can be the o-nitrozaobenzene intermediate itself. This intermediate is prepared by the coupling of an appropriate o-nitroaryl diazonium compound of formula III with an appropriate phenol of formula rv in an acidic or alkaline aqueous medium. If the o-nitroaæobenzene intermediate is coupled in acid medium and then is not care-fully washed with water after its preparation to remove all traces of acid, the o-nitroazobenzene intermediate on storage may become contaminated with traces of iron caused by the corrosive action of residual acid on the steel storage drums used to store the intermediate prior to its later reduction to the 2-aryl-2H-benzot~iazole.
On Table VI the effect of residual iron impuri-ties arising from the o-nitroazobenzene intermediate on product yields are listed. It has been found that such adventitious iron impurities can be removed from the o-nitroazobenzene intermediate conveniently by an aqueous acid reslurry prior to the low alkali reduction process of this invention.
- ::- - : - - , . .
:; ' - . . , :, . '~ . . .-. - -106~266 TABLE VI
Effect of Iron Present from Earlier Preparation o-Nitroazobenzene Intermediate on the Subse~uent Reduction* of the o-Nitroazobenzene Intermediate (Type l) at Constant Ratio of Alkali (0.42 moles) to o-Nitroazobenzene Intermediate (1 mole) ppm Fe from 200-400 ~35 <35 ~35 o-Nitroazobenzene Intermediate First Crop 62 80.779 83 Yield % on Re-duction to 2-aryl-2H-Benzotriazole *Zinc used had "no" ixon present. See Table IV column with "none" for iron content. ppm Fe is based on zinc used.
It is seen from Tables IV-VI that it is the tctal concentration of iron impurities in the reaction system which determines the course of the reaction, and the yield and purity of the desired products regardless of the original source of the iron contamination. The chief sources of iron contamination are the zinc dust and the o-nitroazo-benzene intermediate.
~ rom a practical point of view the iron impurity content of the zinc dust used in this process should never exceed lO0 ppm, preferably not exceed 80 ppm and most preferably be under 50 ppm.
~",,, . ~
-. .
- ~ : ~ : ' , -:
10~2Z66 Likewise, the iron impurity content of the o-nitro-azobenzene intermediate should not exceed 50 ppm (calculated on zinc to be used), preferably not to exceed 35 ppm and most preferably be under 10 ppm.
With these guidelines, the process of this in- -vention is carried out in the presence of a total amount of iron impurities in the reaction system of less than 150 ppm based on zinc used, preferably less than 100 ppm based on zinc used and most preferably less than 50 ppm based on zinc used.
During the coupling step of an appropriate o-nitroaryl diazonium compound of formula III with an appropriate phenol of formula IV in acidic aqueous medium, it is customary to use a wetting agent in order to expedite the coupling reaction in the heterogenous system. Sulfonate wetting agents such as sodium dodecylbenzene sulfonate, which are very soluble in water and which can be thus easily re-moved during isolation of the o-nitroazobenzene intermediate, are much preferred over the less water soluble non-ionic emulsifiers, such as Triton X-151, X-171 and X-800 avail-able commercially from Rohm and Haas, which are more dif-ficult to remove from the o-nitroazobenzene intermediate product of this coupling step. The presence of such ~ 32 -latter emulsifiers in the o-nitroazobenzene intermediates tends to inhibit the subsequent reduction of the o-nitro-azobenzene to the 2-aryl-2H-benzotriazole in the instant process.
The ~-aryl-2H-benzotriazoles have found wide use as dyestuff intermediates, optical brightener blue fluo-rescent agents and selective ultraviolet light absorbing stabilizers affording valuable protection for fibers, films and a variety of polymeric structures subject to deterio-ration by ultraviolet radiation. These materials have become important items of commerce.
The 2-aryl-2H-benzotriazoles are complex organic molecules which require careful synthetic procedures for their production in good yield and acceptable pur-ty.
The present invention is concerned with an im-proved process to prepare ultraviolet stabilizers which are substituted 2-aryl-2H-benzotriazoles. These are dis-tinguished by a very slight absorption in visible light and very high fastness to light in various substrates.
Particularly valuable members of these stabilizers are com-pounds having a free hydroxyl group in the 2-position of the aryl group linked to the 2-nitrogen of the benzotriazole and which are further substituted in the 3- and 5- or the ~- . , . .: , . .
.. . . .
~ 06Z266 4- and 5-positions by lower al~yl groups and may be sub-stituted by a chlorine in the 5-position of the benzotria-zole nucleus.
The description, preparation and uses of these valuable substituted 2-aryl-2H-benzotriazoles are further taught in the U.S. Patent Numbers 3,004,896, 3,055,896, 3,072,585, 3,074,910, 3,189,615 and 3,230,194.
The following examples are given to illustrate the process of the present invention, but are not intended to limlt the scope of the present invention in any manner whatsoever.
- . :- . - . , , . , , . -. ~.
, . .,. . . . ... . ~ : ,. : , . : ,:,:, Example 1 .
2-(2-Hydroxy-3,5-di-tert-am~lphenyl)-2H-~enzotriazole To a 2000 ml. 3-necked, round-bottomed flask equipped with an agitator, reflux condenser, nitrogen in-let and thermometer were charged 155 grams of 2l-hydroxy-3',5'-di-tert-amyl-2-nitroazobenzene, 119 grams of isopropanol and 80 grams of mineral spirits. A
stream of nitrogen was introduced over the surface of the contents of the flask and the nitrogen atmosphere was then maintained throughout the remainder of the reduction process. 13.7 grams of 50~ aqueous sodium hydroxide solu-tion and 222 grams of water were added and the temperature of the contents of the flask were adjusted to 55C. The ratio of the moles of alkali to moles of o-nitroazobenzene intermediate used was 0.42/1. 104 grams of zinc dust was added in 5 portions over a 2 hour period with the tempera-ture of the flask being held at 55-60C with some slight e~ternal cooling. The total concentration of iron impuri-ties from all reactants totalled less than 150 ppm based on zinc used. After all the zinc was added, the tempera-ture was raised to 60C and held at this temperature until a spot test indicated no more o-nitroazobenzene inter-mediate was present. The temperature was then raised to .
. - . . - .
. . - . . . :: . . - :.. :. - ~ :
. ~ ... ,: .
- ,: . : .
.... . . .
: ~ . ... . :
: .-. ' : , 65 and held there for 4 to 5 hours or until TLC analysis indicated that no more of the N-oxy intermediate was present. 62.6 grams of anhydrous sodium sulfate and 35.6 grams of water were then added, the batch was heated to 70C and stirred for 15 minutes~ The material was then allowed to stand and separate into three liquid phases plus unreacted zinc dust. The top two layers containing the desired product were transferred to another flask. The remaini~g aqueous zinc slurry was washed at 65-70C with three successive 16 gram portions of Amsco mineral spirits:
isopropanol ~0:50. The combined product layers and wash liquids were then washed once at 70C with an aqueous hydrochloric acid solution made from 130 grams of water and 40 grams of 32% hydrochloric acid to remove cleavage amine by-products. A second and third wash followed at 70C with aqueous hydrochloric acid solutions made each from 65 grams Gf water and 20 grams of 32% hydrochloric acid. The last wash was essentially colorless. 14 grams of 32%
hydrochloric acid and 220 grams of isopropanol were added to the solution of the product. The batch was allowed to crystallize slowly. The solid product form was filtered and washed with isopropanol at 0C to give 110 grams of 2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole with a melting point of 80-81C. The yield was 77.5% of theory based on the o-nitroazobenzene intermediate.
- - -, : : ~ .~ - -- . : . . . ~ ~
. : . .
- :. , . . -The mother liquor from the first crop material isolated above was extracted with water to remove residual isopropanol. The mineral spirits were removed by distillation to give a residue which was then slurried with sufficient mineral spirits: isopropanol 5G:50 to give an easily agitated slurry. The slurry was filtered at 0C and the isolated solid was washed with isopropanol at 0C to give 6 grams of a second crop of the product with a melting point of 79-80C. The second yield was 4% of theory.
A blend of the first and second crops of the prcduct had a melting point of 80-81 C. This combined blend also passed a stringent heat stability test for transmission after being held at 165C for 4 hours.
The total yield of acceptable product was 116 grams or 81.5~ of theory based on the o-nitroazobenzene intermediate.
Example 2 Isolation of By-Product OH
NH2 ~ t-amyl . HCl t-amyl .. ~
.
~ . . .. - -.
-' ' . ' , ~06Z266 The aqueous hydrochloric acid wash solutions from Example 1 were partially neutralized to pH 5.5 with dilute alkali to yield an easily filterable slurry which was then filtered and dried. The grey solid was isolated in a yield of 2.3 grams or 2% of theory calculated as the hydrochloride salt of 2,4-di-tert-amyl-6-aminophenol.
When the molar ratio of sodium hydroxide to o-nitroazobenzene intermediate was increased to the range of 1.5-2.0 to 1 from the 0.42 to 1 ratio of Example 1, the -yield of cleavage amine by-products rose to the undesirable 11.4% level.
TLC analysis of the solid material isolated in these runs indicated a main aminophenol spot with some minor impurities. Recrystallization of the solid from an isopropanol-hydrochloric acid mixture yielded the pure hydrochloride salt of 2,4-di-tert-amyl-6-aminophenol.
Example 3 ~
2-(2-Hydroxy-3,5-di-tert-amylphenyl)-_ 2H-benzotriazole The same procedure as described in Example 1 was carried out except that the 27.4 grams of 50% sodium hydroxide was used with 155 grams of 2'-hydroxy-3',5'-di-tert-amyl-2-nitroazobenzene to give a ratio of moles of ;
- . .. ... . ..
.. . . . . .
,' ' ' I
~062Z66 alkali to moles of o-nitroazobenzene intermediate of 0.848/1 compared to the ratio of 0.42/1 employed in Ex-ample 1.
. More heat was involved in this case with the temperature of the reaction mixture rising momentarily to 73C with normal external air cooling of the reaction flask.
Complete reduction was accomplished in 1.5 hours at 65C.
The desired product was isolated in the manner described in Example 1, but the sodium sulfate charged was adjusted to give the same sodium ion concentration as i~ Example 1. 50.5 grams of anhydrous sodium sulfate -and 30 grams of water were used in the first product isolation step.
The yield of first crop product was 109 grams, 76.7% of theory based on the o-nitroazobenzene intermediate.
The product had acceptable heat stability properties.
The by-product material corresponding ~-o that de-scribed in Example 2 was isolated in a 10 gram yield of 8.5~ of theory, calculated as the hydrochloride salt of 2,4-tert-amyl-6-aminophenol.
. ~, ., ~, ~ ,,. :. . ,, . -.
.-~ -, ' --. ~;~ ' ' .. . . . .
: , .
, lOf~;Z~;6 The use of more alkali in this case compared to Example 1 decreased reaction time significantly, gave about the same yield of product, but significantly increased the yield of the undesired aminophenol by-product.
Example 3 represents about the upper limit of the range of the present invention in terms of balancing all factors of yield, reaction time and by-product forma-tion for the reduction of o-nitroazobenzene intermediates of Type 1.
The amount of iron impurities in this Example was less than 150 ppm based on the zinc used.
Example 4 2-(2-Hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole The exact procedure and amounts of reactants of Example 1 were used except that 0.03 grams of ferric oxide (a brown powder) was added to the reaction mixture just prior to addition of the zinc dust. The total amount of iron impurities in this system was 210 ppm based on the zinc used compared to a value less than 150 ppm in Example 1.
The ratio of moles of alkali to moles of o-nitroazobenzene was 0.42~1 in both examples.
,. ..
- : : :~ :
- ,:, Complete reduction occurred in S hours at 65C.
~eat-stable product was isolated in a first crop yield of 96.0 grams, 67.6% of theory.
.""." ,,,,-- . .
The amount of by-product isolated was 19.5 grams or 17% of theory calculated as 2,4-di-tert-amyl-6-aminophenol hydrochloride.
!: " , .
The presence of amounts o iron higher than 150 ppm based on zinc used clearly led to reduced yields of desired product and increased yields of cleavage amine by-product even at low alkali to o-nitroazobenzene ratios.
Example 5 i~
2-(2-Hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole When using the procedure of Example 4 the 0.03 grams of ferric oxide was replaced by 2.34 ml of O.O99N
ferric chloride solution, the amount of iron impurities so added to the system were 80 ppm based on the zinc used.
The time for complete reduction to occur was 4 hours and the desired heat-stable product was obtained in a first crop yield of 94.5 grams, 66.5~ of theory. The by-product was isolated in a yield of 18% o theory calcu-lated as 2,4-di-tert-amyl-6-aminophenol hydrochloride.
....
~.
- . ~ :. .. -The yields of product and by-product were essenti-ally the same in both Examples 4 and 5 although far less ferric chloride was added to achieve the same results. This difference is believed due to the physical state (size of particle, dispersibility, and the like) of the iron impuri-ties involved. It is clear that, when the iron is veryfinely dispersed, it took much less of it to effect detri-mentally the yields of the present invention.
The ratio of moles of alkali to moles of o-nitroazobenzene intermediate was O.42/1 in this case.
Exa~ple 6 2-(2-Hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole When using the procedure and quantities of materials described in Example 1, the total amount of iron impurities in the reaction system based on the zinc used was less than 35 ppm, excellent results in terms of reaction time, high yield of heat-stable, first crop reaction product and low yields of undesired cleavage amine by-products were obtained.
Complete reduction occurred a~ 65C in 2.75 hours and the yield of heat-stable, first crop product was 118 grams, 83% of theory based on the o-nitroazobenzene inter-.,;, . .
. . . . .
.: .
-: ., ~ . ' mediate. The yield of the undesired by-product calculated as 2,4-di-tert-amyl-6-aminophenol hydrochloride was only 3% of theory.
The ratio of moles o~ alkali to moles of o-nitro-azobenzene intermediate was 0.42/1 in this case. This, coupled with the low iron impurity content, represents a preferred embodiment of the invention.
_ . .
Example 7 5-Chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole .
When in Example 1, the 2'-hydroxy-3',5'-di-tert-amyl-2-nitroazobenzene was replaced by an equivalent amount of 2'-hydroxy-3',5'-di-tert-butyl-5-chloro-2-nitroazo-benzene, the product 5-chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole was obtained after a reaction time of 5 hours in a yield of 80.4% of theory as an iso-lated product of melting point 151-154C. An additional 4.5% yield was present in the mother liquor for an overall yield of 84.9% of theory.
Example 8 5-Chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole When in Example 7 the 0.42 moles of sodium hydrox-.,~, ~ . . . - ~ -- ' - .
--\
ide per mole of o-nitroazobenzene intermediat~ was replaced by 0.8 moles of sodium hydroxide per mole of o-nitroazo-benzene intermediate and with a reaction time of 2 hours, the product 5-chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole was obtained in an isolated yield of 86.1%
with a melting point of 152-155C~ An additional 1.1%
yield was present in the mother liquor for an overall yield of 87.2% of theory.
Example 3 2-(2-Hydroxy-3-methyl-5-tert-butylphenyl)-2H-benzotriazole When in Example 1, the 2'-hydroxy-3',5'-di-tert-amyl-2-nitroazobenzene was replaced by an equivalent amount of 2'-hydroxy-3'-methyl-S'-tert-butyl-2-nitroazo-benzene, the product 2-(2-hydroxy-3-methyl-5-tert-butyl-phenyl)-2H-benzotriazole was obtained after a reaction time of 5 hours in an isolated yield of 81~ of theory with a melting point of 145-146C.
Example 10 5-Chloro-2(2-hydroxy-3-tert-butyl-5-methylphenyl)-2H-benzotriazole When in Example 1, the 2'-hydroxy-3',5'-di-tert-amyl-2-nitroazobenzene is replaced by an equivalent amount - . . ,,'' ' "' ~ ~,' .' -:: , ...
' .: ' ' ' ': ' ' ' - : ' ' ' ' ' ' ~ ~ ' ~ ' - -of 2'-hydroxy-3'-tert-butyl-5'-methyl-5-chloro-2-nitroazo-benzene and the ratio of the moles of alkali to moles of o-nitroazobenzene intermediate is 0.848/1, the product 5-chloro-2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-2H-benzotriazole is obtained.
Example 11 2-(2-Hydroxy-3-(a-methylbenæyl)-5-methylphenyl)-2H- benzotriazole When in Example 1, the 2'hydroxy-3',5'-di-tert-amyl-2-nitroazobenzene is replaced by an equivalent amount of 2'-hydroxy-3'-(a-methylbenzyl)-5'-methyl-2-nitroazo~enzene, the product 2-(2-hydroxy-3-(-methylbenzyl)-5-methylphenyl)-2H-benzotriazole is obtained.
Example 12 2-(2-Hydroxy-5-methylphenyl)-2H-benzoLriazol2 To a 2000 ml bottom outlet flask equipped with an agitator, reflux condenser, nitrogen inlet and ther-mometer was charged 143.7 grams of 2'-hydroxy-5'-methyl-2-nitroazobenzene (95% purity) followed by 280 ml of toluene. The agitator was started at medium speed and 298 grams of water was then added followed by 54 grams of a 50~ sodium hydroxide solution. The ratio of moles - 45 ~
.., .... .
of sodium hydroxide to moles of o-nitroazo~enzene inter-mediate was 1.2/1. A stream of nitrogen was maintained over the surface of the reaction mixture throughout the remainder of the reaction. In order to saturate the system, some 14.3 grams of previously prepared desired product 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole was added and the temperature of the contents of the flask was adjusted to 45-50C. To the reddish stirred re-action mi~ture was added 107 grams of zinc dust in 5 por-tions over a 2-hour period with the temperature of the reaction mixture being held at 45-50C throughout with some slight external cooling. The total concentration of iron impurities from all reactants totalled less than 150 ppm based on zinc used. After all of the zinc was charged, the temperature was increased to 55C and held for 3 to 4 hours or until TLC analysis indicated that no more N-oxy intermediate was present.
Th~e temperature of the reaction mixture was raised to 70-75C and 18.2 grams of sodium sulfate was added. The batch was moderately agitated for 15 minutes at 70-75C and then allowed to separate into three liquid phases plus unreacted zinc dust. The aqueous zinc layer was split off and saved for recovery. The temperature of the product layers was increased to 75-80C and a solution of 31~ sulfuric acid made from 41.2 grams of 70~ sulfuric acid and 80 grams of water was added. The reaction mixture - . - -....................... ., ... . . . - . .
: . . .. .. . . . . .
: ~ - .. -, - i.. .. . ~ ; '' ~
:1062Z66 was stirred slowly for 15 minutes and then allowed to sepa-rate into layers. The dark sulfuric acid layer was sepa-rated off. The product layer was again extracted with 59.7 grams of 70~ sulfuric acid and finally with 29.9 grams of 70~ sulfuric acid.
The toluene solution of the desired product was held at 75-80C with moderate stirring, treated with 7.5 grams of Filtrol Special Grade No. 4 for 15 minutes and then filtered. The reaction flask was rinsed with 20 ml of toluene which was combined with the product solution.
The product solution was cooled with stirring and the desired product began crystallizing out of solution at 45-50C. The desired product was isolated by filtration, washed with 50 ml of cold isopropanol and vacuum dried at 45-50C to give 93.7 grams of 2-(2-hydroxy-5-methyl-phenyl)-2H-benzotriazole with a melting point of 126-129C.
The yield was 78.5% of theory based on the o-nitroazobenzene intermediate.
The mother liquor contained another 17.2 grams of product or a net amount of 2.9 grams or an additional 2.4% yield. The overall yield of product was 80.9~.
Example 13 2-(2-Hydroxy-5-methylphenyl)-2H-benzotriazole When in Example 1, the 2'-hydroxy-3',5'-di-tert-' : - ' ~ "
amyl-2-nitroazobenzene was replaced by an equivalent amount of 2'-hydroxy-5'-methyl-2-nitroazobenzene and the mole ratio of sodium hydroxide to o-nitroazobenzene intermediate was increased from 0.42/1 to 1.26/1, the reaction went rapidly to yield the product 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole.
Example 14 2-(2-Hydroxy-5-tert-butylphenyl)-2H-benz _riazole When in Example 13, the 2'-hydroxy-5'-methyl-2-nitroazobenzene was replaced by an equivalent amount of 2'-hydroxy-5'-tert-butyl-2-nitroazobenzene, the re-duction reaction went rapidly to yield the product 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole.
Example 15 2-(2-Hydroxy-5-tert-octylphenyl)-2H-benzotriazole When in Example 1, the 2'-hydroxy-3',5'-di-tert-amyl-2-nitroazobenzene was replaced by an equivalent amount of 2'-hydroxy-S'-tert-octyl-2-nitroazobenzene and the moles of sodium hydroxide per mole of o-nitroazobenzene inter-mediate was increased from 0.42/1 to 1.2/1, the product 2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole was obtained in an isolated yield of 62.6% of t~eory with a melting point of 104-107C. The mother liquor contained a compound believed to be an isomer of the desired product.
, :
, "" ' : '.
- . . . . : . ~
-~062266 ~ comparison of Run 7 on Table III shows t~at the use of the 1.26 moles of sodium hydroxide to 1 mole of o-nitroazobenzene of Type 2 led to a commercially sig-nificant 5% increase in isolated yield of pure product compared to Run 8 where a high amount of alkali (3.37/1) was used.
In commercial processes, an increase in yield of 5% can be very significant, both in reducing unit costs, reducing effluent and pollution problems as well as after resulting in a purer product since by-product formation is concomitantly depressed.
In the presence of iron, the yields of desired 2-aryl-2H-benzotriazoles fall off even when the molar ratio of alkali to o-nitroazo intermediate is low and the amount of cleavage amine by-products greatly increased. In Table IV, the effect of adding iron as iron oxide ~Fe2O3) even at the parts per million (ppm) levels based on the charge of zinc is seen. The yield of desired products is greatly affected.
At the 210 ppm level, the yield drops nearly 15% to 67.6%
compared to 82.4% control. Addition of more iron impurities produces even more deleterious results with a greatly en-~hanced~yield of~-undesired-by-produ~t~.
.
.
. .
- '' :
-~, TABLE I'~' Effect of Iron Added as Ferric Oxide on Reduction of o-Nitroazobenzene Intermediate (Type 1) at a Constant Ratio of Alkali (0.42 mole) to o-Nitroazobenzene Intermediate (1 mole) ppm Fe on Zn used 2100 700 210 40 none Time Required at * 7.5 5 4-5 3.75 65 for Complete Reduction (hours) First Crop Yield % * 48.6 67.6 80.582.4 By-Product Material -- 31.2 17.0 2.54.7 Precipitated at p~
5.5 Calculated as Mole % Aminophenol Hydrochloride *Reduction was incomplete and the product formed is the N-oxy compound corresponding to the o-nitroazobenzene intermediate.
The addition of iron impurities as ferric chlo-ride as seen on Table V is even more pronounced. Only 80 ppm of iron based on the zinc charged leads to low yields (66.5~) of the desired 2-aryl-2H-benzotriazole pro-duct.
: .
-^28 -.. ~ - . . , , -- .. - . ~
, :. .
.. , , . . .: -~. : ' , :: . :
-- ? ~ --TABLE V
Effect of Iron Added as Ferric Chloride on Reduction o-Nitroazobenzene Intermediate (Type 1) at a Constant Ratio of Alkali (0.42 mole) to o-Nitroazobenzene Intermediate (1 mole) ppm Fe on Zn used 80 130 First Crop 66.5 59.1 Yield %
By-Product Material 18.5 23.1 Precipitated at pH
5.5 Calculated as Mole % Aminophenol Hydrochloride Commercial zinc dust varies widely in the amount of residual iron impurities ranging from under 100 ppm to over 1500 ppm iron. The latter zinc dusts are totally unacceptable for use with this improved process due to their high iron impurity contents. Zinc dust containing 100 ppm or less iron can be used satisfactorily in the improved process. Preferably the iron content in the zinc dust should be less than 80 ppm and most preferably less than 50 ppm.
The physical state of the iron is also apparently critical. The more finely divided ferric oxide resulting from addition of ferric chloride to the alkaline reduction system proved particularly detrimental compared to the ,. , . .... . . ., :
addition of commercial preformed ferric oxide. The use of more finely divided ferric oxide required iron levels in the 50 ppm range or less for satisfactory results.
Iron can also be introduced into the system from sources other than the zinc dust. Another source of iron present during the reduction step can be the o-nitrozaobenzene intermediate itself. This intermediate is prepared by the coupling of an appropriate o-nitroaryl diazonium compound of formula III with an appropriate phenol of formula rv in an acidic or alkaline aqueous medium. If the o-nitroaæobenzene intermediate is coupled in acid medium and then is not care-fully washed with water after its preparation to remove all traces of acid, the o-nitroazobenzene intermediate on storage may become contaminated with traces of iron caused by the corrosive action of residual acid on the steel storage drums used to store the intermediate prior to its later reduction to the 2-aryl-2H-benzot~iazole.
On Table VI the effect of residual iron impuri-ties arising from the o-nitroazobenzene intermediate on product yields are listed. It has been found that such adventitious iron impurities can be removed from the o-nitroazobenzene intermediate conveniently by an aqueous acid reslurry prior to the low alkali reduction process of this invention.
- ::- - : - - , . .
:; ' - . . , :, . '~ . . .-. - -106~266 TABLE VI
Effect of Iron Present from Earlier Preparation o-Nitroazobenzene Intermediate on the Subse~uent Reduction* of the o-Nitroazobenzene Intermediate (Type l) at Constant Ratio of Alkali (0.42 moles) to o-Nitroazobenzene Intermediate (1 mole) ppm Fe from 200-400 ~35 <35 ~35 o-Nitroazobenzene Intermediate First Crop 62 80.779 83 Yield % on Re-duction to 2-aryl-2H-Benzotriazole *Zinc used had "no" ixon present. See Table IV column with "none" for iron content. ppm Fe is based on zinc used.
It is seen from Tables IV-VI that it is the tctal concentration of iron impurities in the reaction system which determines the course of the reaction, and the yield and purity of the desired products regardless of the original source of the iron contamination. The chief sources of iron contamination are the zinc dust and the o-nitroazo-benzene intermediate.
~ rom a practical point of view the iron impurity content of the zinc dust used in this process should never exceed lO0 ppm, preferably not exceed 80 ppm and most preferably be under 50 ppm.
~",,, . ~
-. .
- ~ : ~ : ' , -:
10~2Z66 Likewise, the iron impurity content of the o-nitro-azobenzene intermediate should not exceed 50 ppm (calculated on zinc to be used), preferably not to exceed 35 ppm and most preferably be under 10 ppm.
With these guidelines, the process of this in- -vention is carried out in the presence of a total amount of iron impurities in the reaction system of less than 150 ppm based on zinc used, preferably less than 100 ppm based on zinc used and most preferably less than 50 ppm based on zinc used.
During the coupling step of an appropriate o-nitroaryl diazonium compound of formula III with an appropriate phenol of formula IV in acidic aqueous medium, it is customary to use a wetting agent in order to expedite the coupling reaction in the heterogenous system. Sulfonate wetting agents such as sodium dodecylbenzene sulfonate, which are very soluble in water and which can be thus easily re-moved during isolation of the o-nitroazobenzene intermediate, are much preferred over the less water soluble non-ionic emulsifiers, such as Triton X-151, X-171 and X-800 avail-able commercially from Rohm and Haas, which are more dif-ficult to remove from the o-nitroazobenzene intermediate product of this coupling step. The presence of such ~ 32 -latter emulsifiers in the o-nitroazobenzene intermediates tends to inhibit the subsequent reduction of the o-nitro-azobenzene to the 2-aryl-2H-benzotriazole in the instant process.
The ~-aryl-2H-benzotriazoles have found wide use as dyestuff intermediates, optical brightener blue fluo-rescent agents and selective ultraviolet light absorbing stabilizers affording valuable protection for fibers, films and a variety of polymeric structures subject to deterio-ration by ultraviolet radiation. These materials have become important items of commerce.
The 2-aryl-2H-benzotriazoles are complex organic molecules which require careful synthetic procedures for their production in good yield and acceptable pur-ty.
The present invention is concerned with an im-proved process to prepare ultraviolet stabilizers which are substituted 2-aryl-2H-benzotriazoles. These are dis-tinguished by a very slight absorption in visible light and very high fastness to light in various substrates.
Particularly valuable members of these stabilizers are com-pounds having a free hydroxyl group in the 2-position of the aryl group linked to the 2-nitrogen of the benzotriazole and which are further substituted in the 3- and 5- or the ~- . , . .: , . .
.. . . .
~ 06Z266 4- and 5-positions by lower al~yl groups and may be sub-stituted by a chlorine in the 5-position of the benzotria-zole nucleus.
The description, preparation and uses of these valuable substituted 2-aryl-2H-benzotriazoles are further taught in the U.S. Patent Numbers 3,004,896, 3,055,896, 3,072,585, 3,074,910, 3,189,615 and 3,230,194.
The following examples are given to illustrate the process of the present invention, but are not intended to limlt the scope of the present invention in any manner whatsoever.
- . :- . - . , , . , , . -. ~.
, . .,. . . . ... . ~ : ,. : , . : ,:,:, Example 1 .
2-(2-Hydroxy-3,5-di-tert-am~lphenyl)-2H-~enzotriazole To a 2000 ml. 3-necked, round-bottomed flask equipped with an agitator, reflux condenser, nitrogen in-let and thermometer were charged 155 grams of 2l-hydroxy-3',5'-di-tert-amyl-2-nitroazobenzene, 119 grams of isopropanol and 80 grams of mineral spirits. A
stream of nitrogen was introduced over the surface of the contents of the flask and the nitrogen atmosphere was then maintained throughout the remainder of the reduction process. 13.7 grams of 50~ aqueous sodium hydroxide solu-tion and 222 grams of water were added and the temperature of the contents of the flask were adjusted to 55C. The ratio of the moles of alkali to moles of o-nitroazobenzene intermediate used was 0.42/1. 104 grams of zinc dust was added in 5 portions over a 2 hour period with the tempera-ture of the flask being held at 55-60C with some slight e~ternal cooling. The total concentration of iron impuri-ties from all reactants totalled less than 150 ppm based on zinc used. After all the zinc was added, the tempera-ture was raised to 60C and held at this temperature until a spot test indicated no more o-nitroazobenzene inter-mediate was present. The temperature was then raised to .
. - . . - .
. . - . . . :: . . - :.. :. - ~ :
. ~ ... ,: .
- ,: . : .
.... . . .
: ~ . ... . :
: .-. ' : , 65 and held there for 4 to 5 hours or until TLC analysis indicated that no more of the N-oxy intermediate was present. 62.6 grams of anhydrous sodium sulfate and 35.6 grams of water were then added, the batch was heated to 70C and stirred for 15 minutes~ The material was then allowed to stand and separate into three liquid phases plus unreacted zinc dust. The top two layers containing the desired product were transferred to another flask. The remaini~g aqueous zinc slurry was washed at 65-70C with three successive 16 gram portions of Amsco mineral spirits:
isopropanol ~0:50. The combined product layers and wash liquids were then washed once at 70C with an aqueous hydrochloric acid solution made from 130 grams of water and 40 grams of 32% hydrochloric acid to remove cleavage amine by-products. A second and third wash followed at 70C with aqueous hydrochloric acid solutions made each from 65 grams Gf water and 20 grams of 32% hydrochloric acid. The last wash was essentially colorless. 14 grams of 32%
hydrochloric acid and 220 grams of isopropanol were added to the solution of the product. The batch was allowed to crystallize slowly. The solid product form was filtered and washed with isopropanol at 0C to give 110 grams of 2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole with a melting point of 80-81C. The yield was 77.5% of theory based on the o-nitroazobenzene intermediate.
- - -, : : ~ .~ - -- . : . . . ~ ~
. : . .
- :. , . . -The mother liquor from the first crop material isolated above was extracted with water to remove residual isopropanol. The mineral spirits were removed by distillation to give a residue which was then slurried with sufficient mineral spirits: isopropanol 5G:50 to give an easily agitated slurry. The slurry was filtered at 0C and the isolated solid was washed with isopropanol at 0C to give 6 grams of a second crop of the product with a melting point of 79-80C. The second yield was 4% of theory.
A blend of the first and second crops of the prcduct had a melting point of 80-81 C. This combined blend also passed a stringent heat stability test for transmission after being held at 165C for 4 hours.
The total yield of acceptable product was 116 grams or 81.5~ of theory based on the o-nitroazobenzene intermediate.
Example 2 Isolation of By-Product OH
NH2 ~ t-amyl . HCl t-amyl .. ~
.
~ . . .. - -.
-' ' . ' , ~06Z266 The aqueous hydrochloric acid wash solutions from Example 1 were partially neutralized to pH 5.5 with dilute alkali to yield an easily filterable slurry which was then filtered and dried. The grey solid was isolated in a yield of 2.3 grams or 2% of theory calculated as the hydrochloride salt of 2,4-di-tert-amyl-6-aminophenol.
When the molar ratio of sodium hydroxide to o-nitroazobenzene intermediate was increased to the range of 1.5-2.0 to 1 from the 0.42 to 1 ratio of Example 1, the -yield of cleavage amine by-products rose to the undesirable 11.4% level.
TLC analysis of the solid material isolated in these runs indicated a main aminophenol spot with some minor impurities. Recrystallization of the solid from an isopropanol-hydrochloric acid mixture yielded the pure hydrochloride salt of 2,4-di-tert-amyl-6-aminophenol.
Example 3 ~
2-(2-Hydroxy-3,5-di-tert-amylphenyl)-_ 2H-benzotriazole The same procedure as described in Example 1 was carried out except that the 27.4 grams of 50% sodium hydroxide was used with 155 grams of 2'-hydroxy-3',5'-di-tert-amyl-2-nitroazobenzene to give a ratio of moles of ;
- . .. ... . ..
.. . . . . .
,' ' ' I
~062Z66 alkali to moles of o-nitroazobenzene intermediate of 0.848/1 compared to the ratio of 0.42/1 employed in Ex-ample 1.
. More heat was involved in this case with the temperature of the reaction mixture rising momentarily to 73C with normal external air cooling of the reaction flask.
Complete reduction was accomplished in 1.5 hours at 65C.
The desired product was isolated in the manner described in Example 1, but the sodium sulfate charged was adjusted to give the same sodium ion concentration as i~ Example 1. 50.5 grams of anhydrous sodium sulfate -and 30 grams of water were used in the first product isolation step.
The yield of first crop product was 109 grams, 76.7% of theory based on the o-nitroazobenzene intermediate.
The product had acceptable heat stability properties.
The by-product material corresponding ~-o that de-scribed in Example 2 was isolated in a 10 gram yield of 8.5~ of theory, calculated as the hydrochloride salt of 2,4-tert-amyl-6-aminophenol.
. ~, ., ~, ~ ,,. :. . ,, . -.
.-~ -, ' --. ~;~ ' ' .. . . . .
: , .
, lOf~;Z~;6 The use of more alkali in this case compared to Example 1 decreased reaction time significantly, gave about the same yield of product, but significantly increased the yield of the undesired aminophenol by-product.
Example 3 represents about the upper limit of the range of the present invention in terms of balancing all factors of yield, reaction time and by-product forma-tion for the reduction of o-nitroazobenzene intermediates of Type 1.
The amount of iron impurities in this Example was less than 150 ppm based on the zinc used.
Example 4 2-(2-Hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole The exact procedure and amounts of reactants of Example 1 were used except that 0.03 grams of ferric oxide (a brown powder) was added to the reaction mixture just prior to addition of the zinc dust. The total amount of iron impurities in this system was 210 ppm based on the zinc used compared to a value less than 150 ppm in Example 1.
The ratio of moles of alkali to moles of o-nitroazobenzene was 0.42~1 in both examples.
,. ..
- : : :~ :
- ,:, Complete reduction occurred in S hours at 65C.
~eat-stable product was isolated in a first crop yield of 96.0 grams, 67.6% of theory.
.""." ,,,,-- . .
The amount of by-product isolated was 19.5 grams or 17% of theory calculated as 2,4-di-tert-amyl-6-aminophenol hydrochloride.
!: " , .
The presence of amounts o iron higher than 150 ppm based on zinc used clearly led to reduced yields of desired product and increased yields of cleavage amine by-product even at low alkali to o-nitroazobenzene ratios.
Example 5 i~
2-(2-Hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole When using the procedure of Example 4 the 0.03 grams of ferric oxide was replaced by 2.34 ml of O.O99N
ferric chloride solution, the amount of iron impurities so added to the system were 80 ppm based on the zinc used.
The time for complete reduction to occur was 4 hours and the desired heat-stable product was obtained in a first crop yield of 94.5 grams, 66.5~ of theory. The by-product was isolated in a yield of 18% o theory calcu-lated as 2,4-di-tert-amyl-6-aminophenol hydrochloride.
....
~.
- . ~ :. .. -The yields of product and by-product were essenti-ally the same in both Examples 4 and 5 although far less ferric chloride was added to achieve the same results. This difference is believed due to the physical state (size of particle, dispersibility, and the like) of the iron impuri-ties involved. It is clear that, when the iron is veryfinely dispersed, it took much less of it to effect detri-mentally the yields of the present invention.
The ratio of moles of alkali to moles of o-nitroazobenzene intermediate was O.42/1 in this case.
Exa~ple 6 2-(2-Hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole When using the procedure and quantities of materials described in Example 1, the total amount of iron impurities in the reaction system based on the zinc used was less than 35 ppm, excellent results in terms of reaction time, high yield of heat-stable, first crop reaction product and low yields of undesired cleavage amine by-products were obtained.
Complete reduction occurred a~ 65C in 2.75 hours and the yield of heat-stable, first crop product was 118 grams, 83% of theory based on the o-nitroazobenzene inter-.,;, . .
. . . . .
.: .
-: ., ~ . ' mediate. The yield of the undesired by-product calculated as 2,4-di-tert-amyl-6-aminophenol hydrochloride was only 3% of theory.
The ratio of moles o~ alkali to moles of o-nitro-azobenzene intermediate was 0.42/1 in this case. This, coupled with the low iron impurity content, represents a preferred embodiment of the invention.
_ . .
Example 7 5-Chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole .
When in Example 1, the 2'-hydroxy-3',5'-di-tert-amyl-2-nitroazobenzene was replaced by an equivalent amount of 2'-hydroxy-3',5'-di-tert-butyl-5-chloro-2-nitroazo-benzene, the product 5-chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole was obtained after a reaction time of 5 hours in a yield of 80.4% of theory as an iso-lated product of melting point 151-154C. An additional 4.5% yield was present in the mother liquor for an overall yield of 84.9% of theory.
Example 8 5-Chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole When in Example 7 the 0.42 moles of sodium hydrox-.,~, ~ . . . - ~ -- ' - .
--\
ide per mole of o-nitroazobenzene intermediat~ was replaced by 0.8 moles of sodium hydroxide per mole of o-nitroazo-benzene intermediate and with a reaction time of 2 hours, the product 5-chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole was obtained in an isolated yield of 86.1%
with a melting point of 152-155C~ An additional 1.1%
yield was present in the mother liquor for an overall yield of 87.2% of theory.
Example 3 2-(2-Hydroxy-3-methyl-5-tert-butylphenyl)-2H-benzotriazole When in Example 1, the 2'-hydroxy-3',5'-di-tert-amyl-2-nitroazobenzene was replaced by an equivalent amount of 2'-hydroxy-3'-methyl-S'-tert-butyl-2-nitroazo-benzene, the product 2-(2-hydroxy-3-methyl-5-tert-butyl-phenyl)-2H-benzotriazole was obtained after a reaction time of 5 hours in an isolated yield of 81~ of theory with a melting point of 145-146C.
Example 10 5-Chloro-2(2-hydroxy-3-tert-butyl-5-methylphenyl)-2H-benzotriazole When in Example 1, the 2'-hydroxy-3',5'-di-tert-amyl-2-nitroazobenzene is replaced by an equivalent amount - . . ,,'' ' "' ~ ~,' .' -:: , ...
' .: ' ' ' ': ' ' ' - : ' ' ' ' ' ' ~ ~ ' ~ ' - -of 2'-hydroxy-3'-tert-butyl-5'-methyl-5-chloro-2-nitroazo-benzene and the ratio of the moles of alkali to moles of o-nitroazobenzene intermediate is 0.848/1, the product 5-chloro-2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-2H-benzotriazole is obtained.
Example 11 2-(2-Hydroxy-3-(a-methylbenæyl)-5-methylphenyl)-2H- benzotriazole When in Example 1, the 2'hydroxy-3',5'-di-tert-amyl-2-nitroazobenzene is replaced by an equivalent amount of 2'-hydroxy-3'-(a-methylbenzyl)-5'-methyl-2-nitroazo~enzene, the product 2-(2-hydroxy-3-(-methylbenzyl)-5-methylphenyl)-2H-benzotriazole is obtained.
Example 12 2-(2-Hydroxy-5-methylphenyl)-2H-benzoLriazol2 To a 2000 ml bottom outlet flask equipped with an agitator, reflux condenser, nitrogen inlet and ther-mometer was charged 143.7 grams of 2'-hydroxy-5'-methyl-2-nitroazobenzene (95% purity) followed by 280 ml of toluene. The agitator was started at medium speed and 298 grams of water was then added followed by 54 grams of a 50~ sodium hydroxide solution. The ratio of moles - 45 ~
.., .... .
of sodium hydroxide to moles of o-nitroazo~enzene inter-mediate was 1.2/1. A stream of nitrogen was maintained over the surface of the reaction mixture throughout the remainder of the reaction. In order to saturate the system, some 14.3 grams of previously prepared desired product 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole was added and the temperature of the contents of the flask was adjusted to 45-50C. To the reddish stirred re-action mi~ture was added 107 grams of zinc dust in 5 por-tions over a 2-hour period with the temperature of the reaction mixture being held at 45-50C throughout with some slight external cooling. The total concentration of iron impurities from all reactants totalled less than 150 ppm based on zinc used. After all of the zinc was charged, the temperature was increased to 55C and held for 3 to 4 hours or until TLC analysis indicated that no more N-oxy intermediate was present.
Th~e temperature of the reaction mixture was raised to 70-75C and 18.2 grams of sodium sulfate was added. The batch was moderately agitated for 15 minutes at 70-75C and then allowed to separate into three liquid phases plus unreacted zinc dust. The aqueous zinc layer was split off and saved for recovery. The temperature of the product layers was increased to 75-80C and a solution of 31~ sulfuric acid made from 41.2 grams of 70~ sulfuric acid and 80 grams of water was added. The reaction mixture - . - -....................... ., ... . . . - . .
: . . .. .. . . . . .
: ~ - .. -, - i.. .. . ~ ; '' ~
:1062Z66 was stirred slowly for 15 minutes and then allowed to sepa-rate into layers. The dark sulfuric acid layer was sepa-rated off. The product layer was again extracted with 59.7 grams of 70~ sulfuric acid and finally with 29.9 grams of 70~ sulfuric acid.
The toluene solution of the desired product was held at 75-80C with moderate stirring, treated with 7.5 grams of Filtrol Special Grade No. 4 for 15 minutes and then filtered. The reaction flask was rinsed with 20 ml of toluene which was combined with the product solution.
The product solution was cooled with stirring and the desired product began crystallizing out of solution at 45-50C. The desired product was isolated by filtration, washed with 50 ml of cold isopropanol and vacuum dried at 45-50C to give 93.7 grams of 2-(2-hydroxy-5-methyl-phenyl)-2H-benzotriazole with a melting point of 126-129C.
The yield was 78.5% of theory based on the o-nitroazobenzene intermediate.
The mother liquor contained another 17.2 grams of product or a net amount of 2.9 grams or an additional 2.4% yield. The overall yield of product was 80.9~.
Example 13 2-(2-Hydroxy-5-methylphenyl)-2H-benzotriazole When in Example 1, the 2'-hydroxy-3',5'-di-tert-' : - ' ~ "
amyl-2-nitroazobenzene was replaced by an equivalent amount of 2'-hydroxy-5'-methyl-2-nitroazobenzene and the mole ratio of sodium hydroxide to o-nitroazobenzene intermediate was increased from 0.42/1 to 1.26/1, the reaction went rapidly to yield the product 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole.
Example 14 2-(2-Hydroxy-5-tert-butylphenyl)-2H-benz _riazole When in Example 13, the 2'-hydroxy-5'-methyl-2-nitroazobenzene was replaced by an equivalent amount of 2'-hydroxy-5'-tert-butyl-2-nitroazobenzene, the re-duction reaction went rapidly to yield the product 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole.
Example 15 2-(2-Hydroxy-5-tert-octylphenyl)-2H-benzotriazole When in Example 1, the 2'-hydroxy-3',5'-di-tert-amyl-2-nitroazobenzene was replaced by an equivalent amount of 2'-hydroxy-S'-tert-octyl-2-nitroazobenzene and the moles of sodium hydroxide per mole of o-nitroazobenzene inter-mediate was increased from 0.42/1 to 1.2/1, the product 2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole was obtained in an isolated yield of 62.6% of t~eory with a melting point of 104-107C. The mother liquor contained a compound believed to be an isomer of the desired product.
, :
, "" ' : '.
Claims (23)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An improved process for the production of 2-aryl-2H-benzotriazoles of the formula I
(I) wherein R1 is hydrogen or chlorine, R2 is hydrogen, chlorine, lower alkyl of 1 to 4 carbon atoms, lower alkoxy of 1 to 4 carbon atoms or alkoxy carbonyl of 2 to 9 carbon atoms, carboxy or -SO3H, R3 is alkyl of 1 to 12 carbon atoms, alkoxy of 1 to 4 carbon atoms, phenyl, phenyl substituted with alkyl groups, said alkyl groups having 1 to 8 carbon atoms, cycloalkyl of 5 to 6 carbon atoms, alkoxy carbonyl of 2 to 9 carbon atoms, chlorine, carboxyethyl or arylalkyl of 7 to 9 carbon atoms, R4 is hydrogen, lower alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 8 carbon atoms, chlorine, or hydroxyl, and R5 is hydrogen, alkyl of 1 to 12 carbon atoms, chlorine, cycloalkyl of 5 to 6 carbon atoms or arylalkyl of 7 to 9 carbon atoms, by the reduction of the corresponding o-nitroazobenzene intermediate with zinc in an aqueous alkali metal hydroxide medium wherein the improvement comprises employing a ratio of moles of alkali to moles of o-nitroazobenzene intermediate in the range of 0.2-1.7/1 in the presence of an amount of the iron impurities in the reaction system of less than 150 ppm based on zinc used.
(I) wherein R1 is hydrogen or chlorine, R2 is hydrogen, chlorine, lower alkyl of 1 to 4 carbon atoms, lower alkoxy of 1 to 4 carbon atoms or alkoxy carbonyl of 2 to 9 carbon atoms, carboxy or -SO3H, R3 is alkyl of 1 to 12 carbon atoms, alkoxy of 1 to 4 carbon atoms, phenyl, phenyl substituted with alkyl groups, said alkyl groups having 1 to 8 carbon atoms, cycloalkyl of 5 to 6 carbon atoms, alkoxy carbonyl of 2 to 9 carbon atoms, chlorine, carboxyethyl or arylalkyl of 7 to 9 carbon atoms, R4 is hydrogen, lower alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 8 carbon atoms, chlorine, or hydroxyl, and R5 is hydrogen, alkyl of 1 to 12 carbon atoms, chlorine, cycloalkyl of 5 to 6 carbon atoms or arylalkyl of 7 to 9 carbon atoms, by the reduction of the corresponding o-nitroazobenzene intermediate with zinc in an aqueous alkali metal hydroxide medium wherein the improvement comprises employing a ratio of moles of alkali to moles of o-nitroazobenzene intermediate in the range of 0.2-1.7/1 in the presence of an amount of the iron impurities in the reaction system of less than 150 ppm based on zinc used.
2. An improved process for the production of 2-aryl-2H-benzotriazoles of the formula I
(I) wherein R1 is hydrogen or chlorine, R2 is hydrogen, chlorine, lower alkyl of 1 to 4 carbon atoms, lower alkoxy of 1 to 4 carbon atoms or alkoxy carbonyl of 2 to 9 carbon atoms, carboxy or -SO3H, R3 is alkyl of 1 to 12 carbon atoms, alkoxy of 1 to 4 carbon atoms, phenyl, phenyl substituted with alkyl groups, said alkyl groups having 1 to 8 carbon atoms, cycloalkyl of 5 to 6 carbon atoms, alkoxy carbonyl of 2 to 9 carbon atoms, chlorine, carboxyethyl or arylalkyl of 7 to 9 carbon atoms, R4 is hydrogen, lower alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 8 carbon atoms, chlorine or hydroxyl, and R5 is alkyl of 1 to 12 carbon atoms, chlorine, cycloalkyl of 5 to 6 carbon atoms or arylalkyl of 7 to 9 carbon atoms, by the reduction of the corresponding o-nitroazobenzene intermediate with zinc in an aqueous alkali metal hydroxide medium wherein the improvement comprises employing a ratio of moles of alkali to moles of o-nitroazobenzene intermediate in the range of 0.2-0.848/1 in the presence of an amount of the iron impurities in the reaction system of less than 150 ppm based on zinc used.
(I) wherein R1 is hydrogen or chlorine, R2 is hydrogen, chlorine, lower alkyl of 1 to 4 carbon atoms, lower alkoxy of 1 to 4 carbon atoms or alkoxy carbonyl of 2 to 9 carbon atoms, carboxy or -SO3H, R3 is alkyl of 1 to 12 carbon atoms, alkoxy of 1 to 4 carbon atoms, phenyl, phenyl substituted with alkyl groups, said alkyl groups having 1 to 8 carbon atoms, cycloalkyl of 5 to 6 carbon atoms, alkoxy carbonyl of 2 to 9 carbon atoms, chlorine, carboxyethyl or arylalkyl of 7 to 9 carbon atoms, R4 is hydrogen, lower alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 8 carbon atoms, chlorine or hydroxyl, and R5 is alkyl of 1 to 12 carbon atoms, chlorine, cycloalkyl of 5 to 6 carbon atoms or arylalkyl of 7 to 9 carbon atoms, by the reduction of the corresponding o-nitroazobenzene intermediate with zinc in an aqueous alkali metal hydroxide medium wherein the improvement comprises employing a ratio of moles of alkali to moles of o-nitroazobenzene intermediate in the range of 0.2-0.848/1 in the presence of an amount of the iron impurities in the reaction system of less than 150 ppm based on zinc used.
3. The process according to claim 2 wherein the ratio of moles of alkali to moles of o-nitroazobenzene intermediate is 0.3-0.7/1.
4. The process according to claim 2 wherein the amount of iron impur-ities in the reaction system is less than 100 ppm based on zinc used.
5. The process according to claim 2 wherein the amount of iron impur-ities is less than 50 ppm based on zinc used.
6. The process according to claim 2 comprising carrying out the reduc-tion reaction in an aqueous polar/non-polar solvent mixture, consisting of isopropand/mineral spirits.
7. The process according to claim 2 for the production of a compound of formula I wherein R1 is hydrogen, R2 is hydrogen, chlorine, lower alkyl of 1 to 2 carbon atoms, methoxy or carboxy, R3 is alkyl of 1 to 8 carbon atoms, cyclohexyl, phenyl, chlorine, .alpha.-methylbenzyl or carboxyethyl, R4 is hydrogen, hydroxyl, methyl or alkoxy of 1 to 8 carbon atoms, and R5 is alkyl of 1 to 8 carbon atoms, chlorine, cyclohexyl, benzyl or .alpha.-methylbenzyl.
8. The process according to claim 2 for production of a compound of formula 1 wherein R1 is hydrogen, R2 is hydrogen or chlorine, R3 is methyl, sec-butyl, tert-butyl, tert-amyl, tert-octyl, cyclohexyl, chlorine or carboxyethyl, R4 is hydrogen, and R5 is chlorine, methyl, tert-butyl, sec-butyl, tert-amyl, tert-octyl or .alpha.-methylbenzyl.
9. The process according to claim 2 for the production of 2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzo-triazole which comprises reducing 2'-hydroxy-3',5'-di-tert-amyl-2-nitroazobenzene in aqueous sodium hydroxide, the ratio of moles of alkali to O-nitroazobenzene being in the range of about 0.42-0.848/1.
10. The process according to claim 2 for the production of 5-chloro-2-(2-hydroxy-3,5-di-tert-butylpheny)-2H-benzotriazole which comprises reduc-ing 2'-hydroxy-3',5'-di-tert-butyl-5-chloro-2-nitroazobenzene in aqueous sodium hydroxide, the ratio of moles of alkali to O-nitroazobenzene being in the range of about 0.42-0.8/1.
11. The process according to claim 2 for the production of 5-chloro-2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-2H-benzotriazole which comprises reducing 2'-hydroxy-3'-tert-butyl-5'-methyl-5-chloro-2-nitroazobenzene in aqueous sodium hydroxide, the ratio of moles of alkali to O-nitroazobenzene being about 0.848/1.
12. The process according to claim 2 for the production of 2-(2-hydroxy-3-(.alpha.-methylbenzyl)-5-methylphenyl)-2H-benzotriazole which comprises reducing 2'-hydroxy-3'-(.alpha.-methylbenzyl)-5'- methyl-2-nitroazobenzene in aqueous sodium hydroxide the ratio of moles of alkali to O-nitroazobenzene being about 0.42/1.
13. An improved process for the production of 2-aryl-2H-benzotriazoles of the formula I
(I) wherein R1 is hydrogen or chlorine, R2 is hydrogen, chlorine, lower alkyl of 1 to 4 carbon atoms, lower alkoxy of 1 to 4 carbon atoms or alkoxy carbonyl of 2 to 9 carbon atoms, carboxy or -SO3H, R3 is alkyl of 1 to 12 carbon atoms, alkoxy of 1 to 4 carbon atoms, phenyl, phenyl substituted with alkyl groups, said alkyl groups having 1 to 8 carbon atoms, cycloalkyl of 5 to 6 carbon atoms, alkoxy carbonyl of 2 to 9 carbon atoms, chlorine, carboxyethyl or arylalkyl of 7 to 9 carbon atoms, R4 is hydrogen, lower alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 8 carbon atoms, chlorine or hydroxyl, and R5 is hydrogen, by the reduction of the corresponding o-nitroazobenzene intermediate with zinc in an aqueous alkali metal hydroxide medium wherein the improve-ment comprises employing a ratio of moles of alkali to moles of o-nitroazo-benzene intermediate in the range of 1.2 to 1.7/1 in the presence of an amount of the iron impurities in the reaction system of less than 150 ppm based on zinc used.
(I) wherein R1 is hydrogen or chlorine, R2 is hydrogen, chlorine, lower alkyl of 1 to 4 carbon atoms, lower alkoxy of 1 to 4 carbon atoms or alkoxy carbonyl of 2 to 9 carbon atoms, carboxy or -SO3H, R3 is alkyl of 1 to 12 carbon atoms, alkoxy of 1 to 4 carbon atoms, phenyl, phenyl substituted with alkyl groups, said alkyl groups having 1 to 8 carbon atoms, cycloalkyl of 5 to 6 carbon atoms, alkoxy carbonyl of 2 to 9 carbon atoms, chlorine, carboxyethyl or arylalkyl of 7 to 9 carbon atoms, R4 is hydrogen, lower alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 8 carbon atoms, chlorine or hydroxyl, and R5 is hydrogen, by the reduction of the corresponding o-nitroazobenzene intermediate with zinc in an aqueous alkali metal hydroxide medium wherein the improve-ment comprises employing a ratio of moles of alkali to moles of o-nitroazo-benzene intermediate in the range of 1.2 to 1.7/1 in the presence of an amount of the iron impurities in the reaction system of less than 150 ppm based on zinc used.
14. The process according to claim 13 wherein the ratio of moles of alkali to moles of o-nitroazobenzene intermediate is 1.2-1.4/1.
15. The process according to claim 13 wherein the amount of iron impur-ities in the reaction is less than 100 ppm based on zinc used.
16. The process according to claim 13 wherein the amount of iron impur-ities in the reaction system is less than 50 ppm based on zinc used.
17. The process according to claim 13 for the production of compounds of claim 1 further comrpising carrying out the reduction reaction in an aqueous/aromatic solvent mixture.
18. The process according to claim 13 for the production of a compound of formula I wherein R1 is hydrogen, R2 is hydrogen, chlorine, lower alkyl of 1 to 2 carbon atoms, methoxy or carboxy, R3 is alkyl of 1 to 8 carbon atoms, cyclohexyl, phenyl, chlorine, a-methylbenzyl or carboxyethyl, R4 is hydrogen, hydroxyl, or alkoxy of 1 to 8 carbon atoms, and R5 is hydrogen.
19. The process according to claim 13 for production of a compound of formula I wherein R1 is hydrogen, R2 is hydrogen or chlorine, R3 is methyl, sec-butyl, tert-butyl, tert-amyl, tert-octyl, cyclohexyl, chlorine or carboxyethyl, R4 is hydrogen, and R5 is hydrogen.
20. The process according to claim 13 for the production of 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole which comprises reducing 2'-hydroxy-5'-methyl-2-nitroazobenzene in aqueous sodium hydroxide, the ratio of alkali to o-nitroazobenzene being in the range of about 1.2-1.26/1.
21. The process according to claim 13 for the production of 2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole which comprises reducing 2'-hydroxy-5'-tert-octyl-2-nitroazobenzene in aqueous sodium hydroxide, the ratio of alkali to o-nitroazobenzene being about 1.2/1.
22. The process according to claim 2 for the production of 2-(2-hydroxy-3-methyl-5-tert-butylphenyl)-2H-benzotriazole which comprises reducing 2'-hydroxy-3'-methyl-5'-tert-butyl-2-nitroazobenzene in aqueous sodium hydroxide, the ratio of alkali to o-nitroazobenzene being about 0.42/1.
23. The process according to claim 13 for the production of 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole which comprises reducing 2'-hydroxy-5'-tert-butyl-2-nitroazobenzene in aqueous sodium hydroxide, the ratio of alkali to o-nitroazobenzene being about 1.26/1.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US52717974A | 1974-11-25 | 1974-11-25 | |
| US05/622,572 US4041044A (en) | 1974-11-25 | 1975-10-15 | Process for the production of 2-aryl-2H-benzotriazoles |
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|---|---|
| CA1062266A true CA1062266A (en) | 1979-09-11 |
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| US (1) | US4041044A (en) |
| CA (1) | CA1062266A (en) |
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| GB (1) | GB1520798A (en) |
Families Citing this family (29)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4219480A (en) * | 1977-09-20 | 1980-08-26 | Ciba-Geigy Corporation | Process for the production of 2-aryl-2H-benzotriazoles |
| US4278589A (en) * | 1978-06-26 | 1981-07-14 | Ciba-Geigy Corporation | 2-[2-Hydroxy-3,5-di-(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole and stabilized compositions |
| US4275004A (en) * | 1978-06-26 | 1981-06-23 | Ciba-Geigy Corporation | High caustic coupling process for preparing substituted 2-nitro-2'-hydroxyazobenzenes |
| US4226763A (en) * | 1978-06-26 | 1980-10-07 | Ciba-Geigy Corporation | 2-[2-Hydroxy-3,5-di-(.alpha.,α-dimethylbenzyl)-phenyl]-2H-benzotriazole and stabilized compositions |
| US4283327A (en) * | 1979-01-25 | 1981-08-11 | Ciba-Geigy Corporation | 2-(2-Hydroxy-3,5-di-tert-octylphenyl)-2H-benzotriazole stabilized compositions |
| US4477614A (en) * | 1979-01-25 | 1984-10-16 | Ciba-Geigy Corporation | 2-[2-Hydroxy-3,5-di-tert-octylphenyl]-2H-benzotriazole stabilized compositions |
| EP0015230B1 (en) * | 1979-01-25 | 1983-02-23 | Ciba-Geigy Ag | Stabilized organic polymer comprising 2-(2-hydroxy-3,5-di-tert-octylphenyl)-2h-benzotriazole as a light-stabilizer |
| US4278590A (en) * | 1979-08-20 | 1981-07-14 | Ciba-Geigy Corporation | 2-[2-Hydroxy-3,5-di-tert-octylphenyl]-2H-Benzotriazole and stabilized compositions |
| US4315848A (en) * | 1979-05-10 | 1982-02-16 | Ciba-Geigy Corporation | 2-[2-Hydroxy-3,5-di-(α,α-dimethylbenzyl)-phenyl]-2H-benzotriazole and stabilized compositions |
| US4347180A (en) * | 1979-05-16 | 1982-08-31 | Ciba-Geigy Corporation | High caustic coupling process for preparing substituted 2-nitro-2'-hydroxyazobenzenes |
| US4383863A (en) * | 1979-12-17 | 1983-05-17 | Ciba-Geigy Corporation | 2-[2-Hydroxy-3,5-di-tert-octylphenyl]-2H-benzotriazole in stabilized photographic compositions |
| EP0031302A3 (en) * | 1979-12-21 | 1981-07-22 | Ciba-Geigy Ag | Benzotriazole uv absorbers, process for their preparation and stabilized mixtures |
| CH647514A5 (en) * | 1981-03-06 | 1985-01-31 | Sandoz Ag | PROCESS FOR PRODUCING CONDENSED triazoles. |
| US4447511A (en) * | 1981-03-06 | 1984-05-08 | Ciba-Geigy Corporation | 2-[2-Hydroxy-3,5-di-tert-octylphenyl]-2H-benzotriazole in stabilized photographic compositions |
| US4709041A (en) * | 1981-11-16 | 1987-11-24 | Polaroid Corporation | 2-(formylphenyl) benzotriazole intermediates |
| DE3476752D1 (en) * | 1983-06-01 | 1989-03-23 | Ciba Geigy Ag | Process for the preparation of 2-arylbenzotriazoles |
| US4981914A (en) * | 1987-08-12 | 1991-01-01 | Atochem North America, Inc. | Polymer bound UV stabilizers |
| US5206378A (en) * | 1987-08-12 | 1993-04-27 | Elf Atochem North America, Inc. | Hydrazido functionalized 2-(2-hydroxyphenyl)-2h-benzotriazoles |
| US5096977A (en) * | 1987-08-12 | 1992-03-17 | Atochem North America, Inc. | Process for preparing polymer bound UV stabilizers |
| US4859759A (en) * | 1988-04-14 | 1989-08-22 | Kimberly-Clark Corporation | Siloxane containing benzotriazolyl/tetraalkylpiperidyl substituent |
| JPH04505002A (en) * | 1989-02-13 | 1992-09-03 | アトケム ノース アメリカ，インコーポレイテッド | Benzotriazole and oxanilide UV absorbing hydrazide |
| EP0424316A3 (en) * | 1989-10-19 | 1991-09-25 | Ciba-Geigy Ag | Purification of 2-aryl-2h-benzotriazoles |
| US5683861A (en) * | 1996-10-23 | 1997-11-04 | Eastman Kodak Company | Benzotriazole-based UV absorbers and photographic elements containing them |
| US5739348A (en) * | 1996-10-23 | 1998-04-14 | Eastman Kodak Company | Method of synthesizing tert-amido-substituted 2-(2'-hydroxyphenyl) benzotriazole compounds in a one-step process |
| EP0975421B1 (en) | 1997-04-15 | 2014-06-18 | Basf Se | Preparation of low-dust stabilisers |
| US6251173B1 (en) | 1999-10-29 | 2001-06-26 | Lexmark International, Inc. | Ink compositions containing ultraviolet absorbers |
| WO2003104341A1 (en) * | 2001-05-10 | 2003-12-18 | Lexmark International, Inc. | Ink compositions containing ultraviolet absorbers |
| AU2001279116A1 (en) * | 2001-08-01 | 2003-02-17 | Lexmark International, Inc. | Ink compositions containing ultraviolet absorbers |
| CN110396070A (en) * | 2019-09-11 | 2019-11-01 | 广东工业大学 | A kind of preparation method of benzotriazole ultraviolet absorber |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2501188A (en) * | 1947-10-22 | 1950-03-21 | American Cyanamid Co | 2-(2'-methyl-4'-amino-5'-methoxyphenyl)-2, 1, 3 benzotriazole |
| DE1185610B (en) * | 1956-12-14 | 1965-01-21 | Geigy Ag J R | Use of 2-phenylbenzotriazole compounds to protect organic substances against ultraviolet radiation |
| US3230194A (en) * | 1961-12-22 | 1966-01-18 | American Cyanamid Co | 2-(2'-hydroxy-5'-tertiary-octylphenyl)-benzotriazole and polyolefins stabilized therewith |
| US3773751A (en) * | 1969-09-08 | 1973-11-20 | American Cyanamid Co | Synthesis of nitroaromatic-azophenols |
| CH529815A (en) * | 1970-06-19 | 1972-10-31 | Ciba Geigy Ag | Use of 2- (2'-hydroxyphenyl) -benzotriazole compounds as light stabilizers |
-
1975
- 1975-10-15 US US05/622,572 patent/US4041044A/en not_active Expired - Lifetime
- 1975-11-19 DE DE19752551853 patent/DE2551853A1/en not_active Ceased
- 1975-11-21 GB GB47940/75A patent/GB1520798A/en not_active Expired
- 1975-11-21 CH CH1512375A patent/CH618690A5/de not_active IP Right Cessation
- 1975-11-24 CA CA240,240A patent/CA1062266A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE2551853A1 (en) | 1976-05-26 |
| US4041044A (en) | 1977-08-09 |
| GB1520798A (en) | 1978-08-09 |
| CH618690A5 (en) | 1980-08-15 |
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