WO1999031081A1

WO1999031081A1 - Ph sensitive photochromic dyes

Info

Publication number: WO1999031081A1
Application number: PCT/GB1998/003681
Authority: WO
Inventors: David A. Clarke; Bernard Mark Heron; Christopher David Gabbutt; John David Hepworth; Steven Michael Partington; Stephen Nigel Corns
Original assignee: James Robinson Limited
Priority date: 1997-12-12
Filing date: 1998-12-10
Publication date: 1999-06-24
Also published as: GB9726361D0

Abstract

Naphthopyrans of formula (I) or (II) reversibly change their optical properties (colour, induced optical density and/or colourability) with changes of pH. In the formulae, R?1 and R2¿ are hydrogen or certain hydrocarbyl or heterocyclic groups, R3 is an amino functional group or certain oxygen, sulphur or phosphorus groups; and R4 may be certain C¿1?-C20 linear or branched alkoxy or alkyl (substituent) groups or is chosen from R?1, R2 or R3¿; and each n is 0 or 1 to 6, the total of all n's being no more than 6.

Description

PH SENSITIVE PHOTOCHROMIC DYES

The present invention relates to photochromic dyes.

Photochromism is a well-known physical phenomenon and has been detailed in "Photochromism: Molecules and Systems" Studies in Organic Chemistry, 40, Eds. H. Dϋrr and H. Bouas-Laurent, Elsevier, 1990. Similarly, the phenomenon of pH sensitive dyes/indicators and stains is well established; (see, for example, 'Colour Chemistry: Synthesis, Properties and Applications of Organic Dyes and Pigments'; H. Zollinger, VCH (Germany) 1991).

The 3H-naphtho[2,l-6]pyran and 2H-naphtho[ 1,2-6] pyran systems are known to be capable of exerting a photochromic effect (see, for example, Y. Hirshberg and E. Fischer, J. Chem. Soc, 1954, 3129 and R. Livingstone et al., J. Chem Soc, 1958, 2422).

The basic 3H-naphtho[2,l-6]pyran and 2H-naphtho[ \,2-b\ pyran structures are illustrated below:

3H-naphtho[2, 1 -bjpyran 2H-naphtho[ 1 ,2-b]pyran The photochromic properties of both the 3H-naphtho[2, l-b]pyran and 2H- naphtho[l,2-b]pyran systems have been intensively studied. For examples of 3H- naphtho[2, l-b]pyrans, see US patent 4,826,977 (1989), US patent 5,066,818 (1991), PCT WO 91/00861 (1991), PCT WO 92/01959 (1992), PCT WO 92/09593 (1992), PCT WO 94/22850 (1994), PCT WO 95/00866 (1995), US patent 5,532, 361 (1996), US patent 5,520,853 (1996), US patent 5,552,090 ( 1996) and PCT WO 97/06455 (1997); and for examples of 2H-naphtho[l,2-b] pyrans, see EP patent 0,250, 193 (1987), US patent 4,818,096 (1989), US patent 5,066,818 (1991), Research Disclosures Pilkington PLC (1992/3), US patent 5,458,814 (1995) and US patent 5,514,817 (1996).

We have now found that changing the pH of a solution, matrix or host material containing certain photochromic dyes can affect the spectroscopic properties, namely those of colour (λ_^J, induced optical density and colourability of the incorporated photochromic dye. Significant shifts in the colour (X_^ together with enhanced induced optical density and improved colourability can be observed without any apparent change in the rate of colouration, though the rate of fade (bleaching) may be altered. This effect is fully reversible and hence provides a means of switching the spectroscopic properties of a photochromic dye by adjusting the pH of its environment. Reversion to the original form of the photochromic dye by adjustment of the pH of its environment results in the return of its associated photochromic properties.

We have further found that, for this new effect to operate, certain structural features of the photochromic molecule are essential, in particular the aromatic moiety of the photochromic dye must have directly bonded to it at least one pH sensitive functional group. Such functional group(s) must contain either (i) one or more one pairs' of electrons that may be reversibly protonated or (ii) one or more acidic protons that may be reversibly removed by the action of a base.

The photochromic dyes of the present invention are naphthopyrans of formula I or II:

(I) (II) wherein R¹ and R², which may be the same or different, are each H, an alkyl group, a substituted alkyl group, an alkenyl group, a substituted alkenyl group, an alkynic group, a substituted alkynic group, a cycloalkyl group, a substituted cycloalkyl group, a heterocycloalkyl group, a substituted heterocycloalkyl group, a cycloalkenyl group, a substituted cycloalkenyl group, an aryl group, a naphthyl group, or a heteroaryl group and their substituted derivatives; R^l and R² may be conjoined to form a ring, for example but not exclusively, cyclopentane, indane, indene, dibenzosuberane, dibenzosuberene, fluorene, xanthene, thioxanthene, acridine and their substituted derivatives particularly alkoxy and amino derivatives as defined below for R³; the or each R³ which may be the same or different is amino, C1-C20 linear or branched alkylamino, C1-C20 linear or branched dialkylamino, C3-C20 cycloalkylamino, C3-C20 substituted cycloalkylamino, C3- C20 cycloalkyl C1-C20 linear or branched alkylamino, C3-C20 substituted cycloalkyl C1-C20 linear or branched alkylamino, C3-C20 dicycloalkylamino, C3- C20 substituted dicycloalkylamino, C3-C20 cycloalkyl arylamino, C3-C20 substituted cycloalkyl arylamino, C 1-C20 linear or branched alkyl arylamino, arylamino, diarylamino, cyclic amino for example but not exclusively aziridino, azetidino, pyrrolidino, piperidino, homopiperidino, perhydroazocino, piperazino, N-alkylpiperazino, N-arylpiperazino, moφholino, thiomoφholino, their substituted derivatives and their mono and di benzologues; aminoaryl in which the amino function is defined as above for R\ bridgehead aminoaryl units such as julolidine and lilolidine; hydroxy, hydroxyaryl, thiol, mercaptoaryl, carboxylic acid, thiocarboxylic acid, sulfur and phosphorus based acids. In the above definition, the terms cycloalkyl and substituted cycloalkyl include bi and tri cycloalkyl amino and substituted derivatives; the or each R⁴ which may be the same or different is C1-C20 linear or branched alkoxy, C1-C20 linear or branched alkylthio, alkyl sulfinyl, alkylsulfonyl, arylsulfinyl, arylsulfonyl, halogen, nitro, nitrile, formyl, acyl, aroyl, acetamido, C2-C10 N-alkylamido, alkoxycarbonyi, aryloxy, arylthio, or is selected from those atoms and groups specified above for R^L, R² and R³; and each 'n' is 0 or an integer from 1 to 6 provided that in any one compound the total of all 'n's is not more than 6.

The effect of a change in pH may be conveniently illustrated by the scheme below:

'deprotonated' 'neutral' 'protonated' photochromic photochromic photochromic molecule molecule molecule

λ_m χl +H- λ 2 +1T λm χ3 low low low absorbance +OH- absorbance +OH- absorbance

absorbance absorbance absorbance

The photochromic and pH colour switching properties exhibited by

the pyran compounds of the present invention render these compounds particularly useful as photochromic/pH sensitive indicators, inks, paints, varnishes and stains

for 'printing' onto paper and fabrics and other surfaces e.g. glass, plastics and

metals. This latter application may be particularly useful for the preparation of

security markers (labels) on a broad range of objects e.g. cheques, bonds, bankers

drafts, credit cards, charge cards and identity documents and cards and discrete

windows. Such inks and other like formulations may also be used for printing

documents and greetings cards. The security/identity uses of these pH sensitive

photochromic compounds and formulations containing them may also extend to

include the marking of fuels e.g. petrol and diesel and other oils.

Furthermore, the materials may be used in sensors, opto-chemical

transducers, optical data recording systems e.g. compact discs, and read/write

optical data storage discs, as waveguides and laser dyes.

Alternatively, these compounds may be incoφorated into polymeric

or sol-gel or colloidal type host materials so as to impart photochromic and pH

colour switching properties to the said host materials.

Examples of applications of the polymeric host materials of the

present invention include the manufacture of lenses for sunglasses and ophthalmic

lenses, protective visors, screens, films, 'plastic' sheeting, containers (e.g. bottles

and other packaging vessels), mirrors, windows and screens for vehicles such as

cars (including sunroofs), motorcycles, aircraft and ships, architectural uses e.g.

glazing, and artistic 'stained glass' windows and for use in novelty items.

Additionally the materials may be used in vehicle body panels including fairings and spoilers, and related external surfaces and other embodiments where it may be

deemed attractive to have said objects change colour in the presence of sunlight.

The photochromic pyrans of the present invention may be

incoφorated into the 'plastic' host material by well established protocols for

example as described in European Patent No. 0254020 or U.S. Patent No.

5,066,818.

Typical host materials may include optically clear polymer materials,

such as polymers of polyol (allyl carbonate) - monomers, polyacrylates such as

polymethylmethacrylates, cellulose acetate, cellulose triacetate, cellulose acetate

propionate, cellulose acetate butyrate, poly( vinyl acetate), poly( vinyl alcohol),

polyuretanes, polycarbonate, polyethylene terephthalate, polystyrene,

poly(triethyleneglycol dimethylacrylate), poly(diethyleneglycol bis(allyl

carbonate)) and various copolymer mixes.

The pH colour switching ability is particularly useful in that a single

manufactured photochromic dye may be used to impart different colours to a

solution, matrix or host material depending upon the pH of the solution, matrix or

host material.

The high induced optical density and enhanced colourability of these

photochromic compounds of the present invention enables the amount of the

photochromic material required so as to impart a useful degree of photochromism

to a polymeric host material or to a solution to be greatly reduced, thereby enabling

a considerable saving of synthetic effort and cost. Furthermore, the use of reduced quantities of the photochromic materials of the present invention has the bonus that

there is a consequent reduction in any undesirable colour that the photochromic

materials may impart in the bleached state either by way of inherent colour of the

material itself or by the formation of coloured fatigue/degradation products through

use of the photochromic material.

The naphthopyrans of the present invention maybe prepared by a

general method which is based on the following reaction scheme:

catalyst solvent

This general synthetic methodology has been described, for example

by L. Merlini in 'Advances in Heterocyclic Chemistry,' 1975, vol. 18, page 159,

and by R. Guglielmetti in "Photochromism: Molecules and Systems," Studies in

Organic Chemistry 40, chap. 8, Eds. H Diirr and H. Bouas-Laurent, Elsevier, 1990,

and also in several patent documents, for example WO 94/22850 and U.S. Patent

No. 5,520,853 (1996). The synthesis of the propargyl alcohols shown in the

scheme above are obtained in a known manner, for example, T. F. Rutledge in

'Acetylenic Compounds,' Reinhold, New York, 1968.

The substituted benzophenones required for the synthesis of the

propargyl alcohols are either commercially available or obtained by documented procedures described in the literature e.g. B. M. Khadilkar et al. Tetrahedron

Letters 1997, 38(9) 1641; J. P. Wolfe et al. Journal of Organic Chemistry, 1997,

62, 1264.

The 1- and 2-naphthols and related hydroxy compounds are either

commercially available or obtained by known synthetic methods, or derived from

such methods; see for example WO 94/22850, W. S. Johnson et al. Organic

Reactions 1951, vol. 6; D. W. Cameron et al. Australian Journal of Chemistry,

1980, 33, 2531.

The catalyst may be selected, for example, from alumina, acetic acid,

trifluoroacetic acid, aryl or alkyl sulfonic acids, silica, clays (e.g. montmorillionite,

tonsil) or acidic exchange resins. Any suitable organic solvent can be used. Those

frequently employed for the reaction include benzene, toluene, xylene and

relatively high boiling alkanes, for example.

In the definition of the naphthopyrans of the invention given above,

the term alkyl group means any linear or branched C1-C20 alkyl group and

includes haloalkyl and perhaloalkyl groups. The term substituted alkyl group

means any linear or branched C1-C20 alkyl group which is substituted in any

position or positions with a functional group which contains the heteroatom

nitrogen or oxygen or sulfur or phosphorus or silicon, or any combination of two

or more of the aforementioned heteroatoms, irrespective of the substituents directly

bonded to said heteroatoms. Additionally, the substituted alkyl group may be

taken to mean any linear or branched C 1-C20 alkyl group which is substituted in any position or positions with a functional group which contains one or more

carbon atoms bonded to one or more of the heteroatoms nitrogen or oxygen or

sulfur or phosphorus or silicon, or any combination of two or more of the

aforementioned heteroatoms, irrespective of the substituents directly bonded to

said heteroatoms.

The term alkenyl group means any isomeric linear or branched C2-

C20 alkenyl group and includes haloalkenyl and perhaloalkenyl groups and may

contain one or more alkene bonds. The term substituted alkenyl group means any

isomeric linear or branched C2-C20 alkenyl group which is substituted in any

position or positions with a functional group which contains the heteroatom

bonded to said heteroatoms. Additionally, the substituted alkenyl group may be

taken to mean any isomeric linear or branched C2-C20 alkenyl group which is

substituted in .any position or positions with a functional group which contains one

or more carbon atoms bonded to one or more of the heteroatoms nitrogen or

oxygen or sulfur or phosphorus or silicon, or any combination of two or more of

the aforementioned heteroatoms, irrespective of the substituents directly bonded to

said heteroatoms.

The term alkynic group means any linear or branched C2-C20

alkynic group and may contain one or more alkynic bonds.

The term cycloalkyl group, a substituted cycloalkyl group, a cycloalkenyl group, and a substituted cycloalkenyl group include mono-, di-, tri-

and tetracyclic C3-C20 containing systems and are defined as for their respective

non-cyclic analogues.

The terms an aryl group and a naphthyl group refer to phenyl and 1-

and 2-naphthyl groups, which are either unsubstituted or substituted with one or

more of the same or different of the following substituents; halogen, C 1-C6 linear

or branched alkyl, C2-C6 linear or branched alkenyl, C2-C6 linear or branched

alkynyl, phenyl, aryl, heteroaryl, C l -C6 linear or branched hydroxyl, C 1-C6 linear

or branched alkoxy, C1-C6 linear or branched alkylthio, alkylsulfinyl,

alkylsulfonyl, amino, C1-C6 alkylamino, C1-C6 substituted alkylamino, C 1-C6

dialkylamino, C 1 -C6 alkylarylamino, diarylamino, cyclic amino for example but

not exclusively pyrrolidino, piperidino, homopiperidino, perhydroazocino,

piperazino, N-substituted piperazino, moφholino thiomoφholino, indolino; nitro,

carboxyalkyl, C1-C6 alkylcarbonyl, benzoyl, aroyl, heteroaroyl, formyl, nirrile,

carboxyamido, or crown and aza crown systems.

The term a heteroaryl group means for example but not exclusively,

any of the following heterocyclic systems and their mono- and di-benzologues and

their mono- and di-naphthologues and their substituted derivatives bonded through

any carbon or heteroatom possible: thiophene, furan, pyrrole, pyrazole, imidazole,

oxazole, isoxazole, thiazole, isothiazole, dithiole, triazole, tetrazole, pyran,

thiopyran, pyridine, pyrimidine, pyridazine, pyrazine, oxazine and dithiin.

As used herein, the term alkoxy group means any linear or branched C 1-C20 alkoxy group and includes haloalkyloxy and perhaloalkyloxy groups, and

the term substituted alkoxy group means any linear or branched C 1-C20 alkoxy

group which is substituted in any position or positions with a functional group

which contains the heteroatom nitrogen or oxygen or sulfur or phosphorus or

silicon, or any combination of two or more of the aforementioned heteroatoms,

irrespective of the substituents directly bonded to said heteroatoms. Additionally,

the substituted alkoxy group may be any linear or branched C1-C20 alkoxy group

which is substituted in any position or positions with a functional group which

contains one or more carbon atoms bonded to one or more of the heteroatoms

bonded to said heteroatoms.

As used herein, the term alkylthio group means any linear or

branched C1-C20 alkylthio group and includes (as the alkyl part) haloalkyl and

perhaloalkyl groups, and the term substituted alkylthio group means any linear or

branched C1-C20 alkylthio group which is substituted in any position or positions

with a functional group which contains the heteroatom nitrogen or oxygen or sulfur

or phosphorus or silicon, or any combination of two or more of the aforementioned

heteroatoms, irrespective of the substituents directly bonded to said heteroatoms.

Additionally, the substituted alkyl group may be any linear or branched C 1-C20

alkylthio group which is substituted in any position or positions with a functional

group which contains one or more carbon atoms bonded to one or more of the heteroatoms nitrogen or oxygen or sulfur or phosphorus or silicon, or any

combination of two or more of the aforementioned heteroatoms, irrespective of the

substituents directly bonded to said heteroatoms.

In order that the invention may be more fully understood, the

following examples are given by way of illustration only:

Example 1

(1) 6-Moφholino-3(4-piperidinophenyl)-3-phenyl-3H-naphtho[2, l-b]pyran

A solution of 4-moφholino-2-naphthol (6.5 mmol) and l-(4-

piperidinophenyl)-l-phenylprop-2-yn-l-ol (6.5 mmol) in toluene (65 cm³)

containing acidic alumina (Brockmann 1) (4.0g) was refluxed for 60 minutes. The

cooled solution was filtered and the alumina was washed well with EtOAc

(200 cm³). Removal of the solvent from the filtrate gave an oil which solidified on

standing at room temperature. Recrystallisation from EtOAc/hexane gave 6-

moφholino-3(4-piperidinophenyl)-3-phenyl-3H-naphtho[2, l-b]pyran (73%), m.p.

= 170.5-172°C.

Examples 2 to 18

Following an identical protocol, but using the appropriate naphthol and

prop-2-yn-l-ol, the following naphthopyrans were obtained: (2) 3 (4-Methoxyphenyl)-6-moφholino-3 (4-piperidinophenyl)-3H-naphtho-

[2, l-b]pyran from 4-moφholino-2-naphthol and l-(4-methoxyphenyl)-l-(4-

piperidinophenyl)prop-2-yn-l-ol (75%) after recrystallisation from EtOAc, hexane

and ethanol, m.p. = 247-249°C.

(3) 3^-Di(4-methoxyphenyl)-6-morpholino-3H-naphtho[2,l-&]pyran from 4- morpholino-2-naphthol and l,l-di(4-methoxyphenyl)prop-2-yn-l-ol (68 %) after recrystallisation from EtOAc, hexane and a trace of ethanol, m.p. = 211-213 °C.

(4) 6-Mo holmo-3^-di(4-pyιτoUdmophenyl)-3H-naphtho[2,l-&]p5^an from 4-morpholino-2-naphthol and l,l-di(4-pyrrolidinophenyl)prop-2-yn-l-ol (56 %) after recrystallisation from EtOAc and, m.p. = 243-245 °C.

(5) 6-Morpholino-3-(4-methoxyphenyl)-3-phenyl-3H-naphtho[2,l-b]pyran from 4-morpholino-2-naphthol and l-(4-methoxyphenyl)-l-phenylprop- 2-yn-l-ol (71 %) after recrystallisation from hexane and a trace of EtOAc, m.p. = 164.5-165.0 °C).

(6) 6^mdolincH3^-di(4-methoxyphenyl)-3H-rιaphtho[2,l-&]pyran from 4- indolino-2-naphthol and l,l-di(4-methoxyphenyl)prop-2-yn-l-ol (57 %) after recrystallisation from EtOAc and hexane, m.p. = 171-172 °C

(7) Methyl 9-morpholino-2^-di(4-methoxyphenyl)-2H-naphtho[l,2-&]pyran- 5-carboxylate from methyl 4-hydroxy-6-morpholinonaphthalene-2- carboxylate and l,l-di(4-methoxyphenyl)prop-2-yn-l-ol (42 %) after recrystallisation from EtOAc and hexane, m.p. = 153.5-155 °C.

(8) Methyl 9-morpholino-2-(4-morpholinophenyl)-2-phenyl-2H-naphtho [l,2-Σ?]pyran-5-carboxylate from methyl 4-hydroxy-6- morpholinonaphthalene-2-carboxylate and l-(4-morpholinophenyl)-l- phenylprop-2-yn-l-ol (74 %) after recrystallisation from EtOAc and hexane, m.p. = 248-250 °C.

(9) 5-Hydroxy-3^-di(4-methoxyphenyl)-3H-naphtho[2,l-&]pyran from 2,3- dihydroxynaphthalene and l,l-di(4-methoxyphenyl)prop-2-yn-l-ol (53 %) after recrystallisation from EtOAc, hexane and a trace of ethanol, m.p. = 150.5-152 <>C.

(10) 6^(4_^N,N-Diethylarn ophenyl)-2 di(4-methoxyphenyl)-2H-naphtho. [l,2-b]pyran from 4-(4-N,N-diethylanilino)-l-naphthol and l,l-di(4- methoxyphenyl)prop-2-yn-l-ol (61 %) after recrystallisation from EtOAc and hexane, m.p. = 147.5-149.5 °C.

(11) 6-Morpholino-3 -diphenyl-3H-naphtho[2,l-b]pyran from 4-morpholino- 2-naphthol and l-l-diphenylprop-2-yn-l-ol (55 %) after recrystallisation from toluene and MeOH, m.p. = 187 -188 °C.

(12) 3-(2,4-Dmnethoxyphenyl)-3-(4-methoxyphenyl)-6-morpholino-3H- naphtho[2,l-b]pyran from 4-morpholino-2-naphthol and l-(2,4- dimethoxyphenyl)-l-(4-methoxyphenyl)prop-2-yn-l-ol (68 %) after recrystallisation from hexane and a trace of EtOAc, m.p. = 163-165 °C.

(13) 3,3-Di-(4-methoxyphenyl)-3H-naphtho[2,l-&]pyran from 2-naphthol and l,l-di-(4-methoxyphenyl)prop-2-yn-l-ol (48 %) after recrystallisation from hexane and a trace of EtOAc, m.p. = 175. -177 °C.

(14) 3 -Di(4-methoxyphenyl)-6-piperidino-3H-naphtho[2,l-&]pyran from 4- piperidino-2-naphthol and l,l-di(4-methoxyphenyl)prop-2-yn-l-ol (73%) after recrystallisation from EtOAc, hexane and a trace of ethanol, m.p. = 114-119 °C.

(15) 6-Morpholino-3(4-morpholinophenyl)-3-phenyl-3H-naphtho[2,l-&]pyran from 4-morpholino-2-naphthol and l(4-morpholinophenyl)-l- phenylprop-2-yn-l-ol (73%) after recrystallisation from EtOAc / hexane, m.p. = 187-188 °C.

(16) 6-Morpholino-3-phenyl-3(4-pyrrolidinophenyl)-3H-naphtho[2,l-b]pyran from 4-morpholino-2-naphthol and l-phenyl-l(4-pyrrolidinophenyl)- prop-2-yn-l-ol (66%) after recrystallisation from EtOAc, hexane and a trace of ethanol, m.p. = 220-222 °C.

(17) 3^-Di(4-N,N-di-methylai-rdnophenyl)-6-mor 3holmo-3H-riaphtho[2,l-&]- pyran from 4-morpholino-2-naphthol and l,l-di(4-N,N-dimethylamino- phenyl)prop-2-yn-l-ol (69%) after recrystallisation from EtOAc, hexane and a trace of ethanol, m.p. = 258.5-260.5 °C.

(18) 3 -Di(4-N,N-diethylaminophenyl)-6-morpholino-3H-naphtho[2,l-b]- pyran from 4-morpholino-2-naphthol and l,l-di(4-N,N-diethylamino- phenyl)prop-2-yn-l-ol (78%) after recrystallisation from EtOAc / hexane, m.p. = 235 -238 °C.

The photochromic properties of each of the naphthopyrans made in

Examples 1 to 14 were measured and the results are set out in the following Table.

NOTES

1. abs = absorbance of the photochromic dye in spectroscopic grade acetone

prior to activation by a light source.

2. abs* = absorbance of the photochromic dye in spectroscopic grade acetone

subsequent to activation by a light source.

3. All solutions are of a similar concentration ca. lmmoldm^'3.

4. The irradiation sequence was identical for all solutions.

5. The term 'neutral species' refers to the photochromic dye prior to

modification with acid or base.

6. The term 'modified species' refers to the photochromic dye subsequent to

treatment by acid or base.

Claims

CLAIMS:

1. A naphthopyran of the formula I or II:

(I) (II)

wherein R¹ and R², which may be the s.ame or different, are each H, an alkyl group,

a substituted alkyl group, an alkenyl group, a substituted alkenyl group, an alkynic

group, a substituted alkynic group, a cycloalkyl group, a substituted cycloalkyl

group, a heterocycloalkyl group, a substituted heterocycloalkyl group, a

cycloalkenyl group, a substituted cycloalkenyl group, an aryl group, a naphthyl

group, or a heteroaryl group; R¹ and R² may be conjoined to form a ring which

may be substituted; the or each R\ which may be the same or different, is an

amino function which is amino, C 1-C20 linear or branched alkylamino, C1-C20

linear or branched dialkylamino, C3-C20 cycloalkyamino, C3-C20 substituted cycloalkylamino, C3-C20 cycloalkyl C1-C20 linear or branched alkylamino, C3-

C20 substituted cycloalkyl C 1-C20 linear or branched alkylamino, C3-C20

dicycloalkylamino, C3-C20 substituted dicycloalkylamino, C3-C20 cycloalkyl

arylamino, C3-C20 substituted cycloalkyl arylamino, C 1-C20 linear or branched

alkyl arylamino, arylamino, diarylamino, cyclic amino or a substituted cyclic

amino derivative or a mono or di benzologue thereof; or aminoaryl in which the

amino function is defined as above for R³, or a bridgehead aminoaryl unit; or

hydroxy, hydroxyaryl, thiol, mercaptoaryl, carboxylic acid, thiocarboxylic acid,

sulfur or phosphorus based acid; and the or each R⁴, which may be the same or

different, is C1-C20 linear or branched alkoxy, C1-C20 linear or branched

alkylthio, alkylsulfinyl, alkylsulfonyl, arylsulfinyl, arylsulfonyl, halogen, nitro,

nitrile, formyl, acyl, aroyl, acetamido, C2-C10 N-alkylamido, alkoxycarbonyl,

aryloxy, arylthio, or is selected from those atoms and groups specified above for

R^l, R² and R³; and each 'n' is 0 or an integer from 1 to 6 provided that in any one

compound the total of all 'n's is not more than 6.

2. A naphthopyran according to claim 1, wherein R¹ and R² are

conjoined to form a ring which is a substituted or unsubstituted cyclopentane,

indane, indene, dibenzosuberane, dibenzosuberene, fluorene, xanthene,

thioxanthene or acridine ring.

3. A naphthopyran according to claim 2, wherein the said ring is substituted with at least one alkoxy or amino group.

4. A naphthopyran according to claim 1, 2 or 3, wherein R³ is an amino

function which is a cyclic amino group selected from aziridino, azetidino,

pyrrolidino, piperidino, homopiperidino, perhydroazocino, piperazino, N-

alkylpiperazino, N-arylpiperazino, mo╧åholino and thiomo╧åholino.

5. A naphthopyran according to claim 1, 2 or 3, wherein R³ is a

bridgehead aminoaryl unit which is juloidine or lilolidine.

6. 6-Mo╧åholino-3(4-piperidinophenyl)-3-phenyl-3H-naphtho[2, 1 -

b]pyran, 6-mo╧åholino-3(4-mo╧åholinophenyl)-3-phenyl-3H-naphtho[2, 1 -b]pyran,

3(4-methoxyphenyl)-6-mo╧åholino-3(4-piperidinophenyl)-3H-naphtho-[2, l-

6]py╧äan, 6-mo╧åholino-3(4-pyrrolidinophenyl)-3-phenyl-3H-naphtho[2, 1 -b]pyran

3,3-di(4-methoxyphenyl)-6-mo╧åholino-3H-naphtho[2, 1 -bjpyran,

6-mo╧åholino-3,3-di(4-pyrrolidinophenyl)-3H-naphtho[2, 1 -b]pyran, 6-mo╧åholino-

3,3-di(4-NN-dimemylaminophenyl)-3H-naphth[2,l-b]pyran, 6-mo╧åholino-3,3-

di(4-NN-diethylaminophenyl)-3H-naphtho[2, l-b]pyran, 6-mo╧åholino-3-(4-

methoxyphenyl)-3-phenyl-3H-naphtho[2, l-b]pyran, 6-indolino-3,3-di(4-

methoxyphenyl)-3H-naphtho[2, l-b]pyran, methyl 9-mo╧åholino-2,2-di(4-

methoxyphenyl)-2H-naphtho[ l,2-b]pyr^-5-carboxylate, methyl 9-mo╧åholino-2-

(4-mo╧åholinophenyl)-2-phenyl-2H-naphtho[l,2-b]pyran-5-carboxylate, 5- hydroxy-3,3-di(4-methoxyphenyl)-3H-naphtho[2, l-b]pyran, 6-(4-NN-

diethylaminophenyl)-2,2-di(4-methoxyphenyl)-2H-naphtho[ l,2-b]pyran, 6-

mo╧åholino-3,3-diphenyl-3H-naphtho[2,l-b]pyran, 3-(2,4-dimethoxyphenyl)-3-(4-

methoxyphenyl)-6-mo╧åholino-3H-naphtho[2, l-b]pyran, 3,3-di-(4-

methoxyphenyl)-3H-naphtho[2, l-b]pyran and 3,3-di(4-methoxyphenyl)-6-

piperidino-3H-naphtho[2, 1 -b]pyran.

7. A process for making a naphthopyran as defined in claim 1, which

includes the step:

the above compounds including R³ and/or R⁴ substituents as desired in accordance

with claim 1.

8. A process for making a naphthopyran as defined in claim 1

catalyst solvent

substantially as herein described in any of Examples 1 to 14.

9. An article, device or composition which comprises a naphthopyran as claimed in claim 1, and a carrier therefor.

10. An article according to claim 9, wherein the carrier is a polymeric

material.

11. An ophthalmic element which comprises a naphthopyran as claimed

in claim 1.

12. The use of a composition according to claim 9 for labelling, printing,

marking or painting.

13. The use of a composition according to claim 9, for characterisation,

identification or security marking.