Photochromic compounds

A spiro (indolino) oxazine compound of general formula (I) ##STR1## wherein R.sub.1 represents a group of the formula --NR.sub.2 R.sub.3 wherein each of R.sub.2 and R.sub.3, which may be the same or different, independently represents an alkyl group, or a carbocyclic group, preferably aryl, or a heterocyclic group, or R.sub.2 and R.sub.3 taken together with the nitrogen atom to which they are attached represent a heterocyclic ring having one or more heteroatoms and which may optionally carry at least one substituent selected from alkyl, aryl or heteroaryl groups; PA1 --X-- is selected from --O--, --S--, --Se--, --NH-- or --NR-- wherein R represents an alkyl group, and PA1 ring A is a carbocyclic or heterocyclic ring which can be optionally substituted with a group of formula R.sub.8 as defined above, or may optionally have a carbocyclic or heterocyclic ring fused thereto; and wherein R.sub.4 -R.sub.8 are as defined in the specification. The spiro (indolino) oxazine compounds of the invention are useful as photochromic materials.

The present invention relates to certain novel photochromic spiro 
(indolino) oxazine compounds, and to articles and compositions containing 
them. 
Photochromism is a well-known physical phenomenon which is observed with 
certain classes of chemical compounds. A detailed discussion of this 
phenomenon can be found in "Photochromism: Molecules and Systems", Studies 
in Organic Chemistry 40, Edited by H. Durr and H. Bouas-Laurent, Elsevier 
1990. 
Spiro oxazine compounds as a class of compounds are known to be capable of 
exhibiting a photochromic effect. For example, European Patent 
specification No. 0358774 describes a series of photochromic spiro oxazine 
compounds which are said to have an excellent resistance to fatigue and 
also provide a number of different colour hues. 
U.S. Pat. No. 4,986,934 describes various spiro-benzoxazine pyrrolo 
pyridine compounds. 
Our European Patent No. 0245020 describes a number of spiro-oxazine 
photochromic compounds all of which are characterised by the presence of 
an amine functionality at the 6'-position of the molecule. The compounds 
described in this patent specification are found to have an intense dark 
colouration in their darkened state. 
We have now found a group of other spiro (indolino) oxazine compounds which 
also provide an intense dark colouration in their darkened state. One of 
the important characteristics of the novel spiro (indolino) compounds of 
the present invention is that they carry a substituted amino group in the 
6'-position of the molecule. 
Accordingly, the present invention provides a spiro (indolino) oxazine 
compound of general formula (I): 
##STR2## 
wherein R.sub.1 represents a group of the formula --NR.sub.2 R.sub.3 
wherein each of R.sub.2 and R.sub.3, which may be the same or different, 
independently represents an alkyl group, or a carbocyclic group, 
preferably aryl, or a heterocyclic group, or R.sub.2 and R.sub.3 taken 
together with the nitrogen atom to which they are attached represent a 
heterocyclic ring having one or more heteroatoms and which may optionally 
carry at least one substituent selected from alkyl, aryl or heteroaryl 
groups; 
R.sub.4 represents an alkyl group which may be linear, branched or 
alicyclic; 
each of R.sub.5 and R.sub.6, which may be the same or different, represents 
an alkyl group or a carbocyclic or heterocyclic group, or R.sub.5 and 
R.sub.6 taken together with the carbon atom to which they are attached 
represent a carbocyclic or heterocyclic ring which may optionally carry at 
least one substituent selected from alkyl, aryl or heteroaryl groups; 
R.sub.7 represents a hydrogen atom or an alkyl, aryl or heteroaryl group, 
or a carbocyclic or heterocyclic group which is fused to heterocyclic ring 
B; 
R.sub.8 represents a hydrogen atom or a substituent selected from alkyl, 
alkoxy, aryl, aryloxy, heteroaryl, halogen, azo, imino, amide, ester, 
cyano, trifluoromethyl or nitro group, or a dialkylamino group; 
--X-- is selected from --O--, --S--, --Se--, --NH-- or --NR-- wherein R 
represents an alkyl group, and 
ring A is a carbocyclic or heterocyclic ring which can be optionally 
substituted with a group of formula R.sub.8 as defined above, or may 
optionally have a carbocyclic or heterocyclic ring fused thereto. 
For the avoidance of doubt, throughout this specification, the ring 
numbering system used to describe the spiro-oxazine compounds of the 
present invention is as follows: 
##STR3## 
The spiro (indolino) oxazine compounds of the present invention exhibit 
very dark colouration (typically red, but also including other colours up 
to blue) in the darkened condition when compared with the colouration 
obtained with the corresponding materials which have no amino substituent 
in the 6'-position of the molecule. 
The photochromic materials of the present invention which give a red 
colouration in the darkened state are particularly useful for mixing with 
complimentary spiro-oxazine compounds which exhibit a green colouration in 
their darkened condition. Typical compounds which give this green 
colouration are described in our U.K. patent application No. 9225346. By 
mixing the present compounds with such green photochromic compounds one 
can obtain a composite mixture of photochromic compounds which produces a 
neutral or grey colouration in the darkened state; this can be useful for 
certain tinted lenses, e.g. in sunglasses. 
A further advantage of the photochromic materials of the present invention 
is that they are extremely efficient absorbers of long wave U.V. radiation 
(340-400 nm: UVa radiation) and are therefore very sensitive to actinic 
radiation. This means that these materials provide additional protection 
against UV irradiation. 
Preferred spiro-oxazines in accordance with the invention are compounds of 
general formula (I) in which --X-- is --O-- (so as to form a furan ring), 
the group R.sub.7 is a benzene ring fused to the said furan ring, and 
R.sub.8 is a hydrogen atom, i.e. a compound of general formula (II): 
##STR4## 
wherein R.sub.1, R.sub.4, R.sub.5, R.sub.6 and Ring A are as defined 
above. 
Preferably ring A is a benzene ring or a benzene ring carrying an alkoxy 
group (usually a methoxy group) in the 5-position; or a pyridine ring with 
the nitrogen atom in the 7-position, optionally substituted with a single 
CF.sub.3 - group in the 5- or 6-position or substituted with two CF.sub.3 
- groups in the 4- and 6-positions of the ring; or a pyrazine ring with 
nitrogen atoms in both the 4- and 7- positions of the ring. 
Throughout this specification, unless stated otherwise, the term "alkyl" is 
to be taken to mean an alkyl group having from 1 to 4 carbon atoms. 
Similarly, the term "alkoxy" is to be taken to mean an alkoxy group having 
from 1 to 4 carbon atoms. 
Furthermore, in the definitions given above for R.sub.1, R.sub.5, R.sub.6 
and R.sub.7, whenever reference has been made to a carbocyclic or 
heterocyclic ring (or group), unless specified otherwise it is to be 
understood that such carbocyclic or heterocyclic rings (or groups) may be 
unsubstituted or may carry one or more substituents chosen from halogen 
atoms, alkyl, alkoxy, aryl, aryloxy, heteroaryl, amino, substituted amino, 
azo, imino, amide, carboxylate, ester, cyano, trifluoromethyl or nitro 
groups, or, further, such rings may have one or more further rings which 
are fused thereto. 
For the avoidance of doubt, in the definition of R.sub.1 above, the group 
--NR.sub.2 R.sub.3 includes within its scope ring systems in which one or 
more further rings are fused to the heterocyclic ring, and such ring 
systems may incorporate saturated and/or unsaturated rings. 
Preferably, the R.sub.1 substituent is a piperidino group or a morpholino 
group. 
Preferably, the R.sub.4 -substituent is a C.sub.1-8 alkyl group, typically 
a methyl group, an isobutyl group or a neopentyl group. 
Each of the R.sub.5 and R.sub.6 substituents is preferably a C.sub.1-8 
alkyl group, typically a methyl group, an isobutyl group or a neopentyl 
group, or the R.sub.5 and R.sub.6 groups together with the carbon atom to 
which they are attached preferably represent a spirohexyl group. 
According to a further aspect of the present invention, there is provided a 
process for preparing a spiro (indolino) oxazine compound of general 
formula (I), which process comprises 
(a) oxidising a compound of general formula (II) 
##STR5## 
wherein X, R.sub.7 and R.sub.8 are as defined above, by use of oxygen in 
the presence of a complex of a copper (II) salt and an amine of formula 
R.sub.1 H to yield a compound of formula (III) 
##STR6## 
wherein X, R.sub.1, R.sub.7 and R.sub.8 are as defined above, (b) heating 
the compound of formula (III) with hydroxylamine hydrochloride under 
reflux to yield a nitroso-hydroxy compound of formula (IV) 
##STR7## 
wherein X, R.sub.1, R.sub.7 and R.sub.8 are as defined above, and (c) 
condensing the nitroso-hydroxy compound of formula (IV) with a 
2-alkylidene indole compound of formula (V) 
##STR8## 
wherein R.sub.4, R.sub.5, R.sub.6 and ring A are as defined above. 
The novel spiro (indolino) oxazine compounds of the present invention are 
found to be particularly useful as photochromic materials to be 
incorporated into polymeric host materials so as to impart photochromic 
properties to the said polymeric host materials. 
The photochromic compounds of the present invention are incorporated into 
the plastics host material in known manner, for example as described in 
European Patent No. 0245020 or U.S. Pat. No. 5,066,818. 
The spiro-oxazine compounds of the invention exhibit substantially greater 
induced optical density (IOD) than prior art materials of comparable 
structure. As a result, the amount of photochromic material required to 
impart a useful degree of photochromism to a polymeric host material or to 
a solution is greatly reduced when compared to the amount required to 
obtain an equivalent photochromic effect with prior art photochromic 
materials. 
The use of reduced quantities of the photochromic materials of the 
invention not only gives a saving in cost, but also has the added 
advantage that there is a consequent reduction in any undesirable colour 
that the photochromic materials may impart in the bleached state, either 
by way of the inherent colour of the photochromic material itself, or by 
way of any coloured degradation/fatigue products that may be generated 
during use of the photochromic material. 
The colour range of the spiro (indolino) oxazine compounds of the present 
invention is 490 to 610 nm; thus, the materials of the present invention 
impart a red or purple or blue colouration in their darkened state. In the 
faded or bleached condition the materials exhibit a colourless or pale 
colouration. 
Typical polymeric host materials are 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), polyurethanes, polycarbonates, polyethylene 
terephthalate, polystyrene, styrene/methylmethacrylate copolymers, 
styrene/acrylonitrile copolymers, and polyvinylbutyral. Transparent 
copolymers and blends of the transparent polymers are also suitable as 
host materials. Polymers of the type described in EP 0294056 or EP 0453149 
are also suitable. 
Preferably, the polymeric host material is an optically clear polymerized 
organic material such as a polyurethane or a polymer of diethylene glycol 
bis(allyl carbonate) (sold under the trade name CR-39), or SPECTRALITE--a 
material sold by Sola Optical USA. 
Usually, the amount of photochromic spiro oxazine compound incorporated in 
the polymeric host material ranges from 0.001 to 0.5 wt %, based on the 
weight of the polymeric host material. 
In some applications, it may be desirable or advantageous to combine the 
spiro oxazine compounds of the present invention with other photochromic 
materials to obtain an aggregate colour effect. For example, other known 
spiro-oxazine materials may have a colour range of 530 to 680 nm which 
means that in the darkened condition the spiro-oxazines impart a 
red-purple or purple or blue or blue-green or green colouration to a host 
material. Thus, the present spiro-oxazine compounds are complementary to 
known spiro-oxazine materials such as those described in our European 
Patent No. 0245020, or in our UK Patent Applications Nos. 92/25346, 
92/25347 and 92/25348, or to the spiro (indolino) naphthoxazines, spire 
(indolino) pyrido benzoxazines and spiro (indolino) benzoxazines described 
in U.S. Pat. Nos. 4,637,698, 3,562,172, 3,578,602, 4,816,584, 4,215,010 
and 4,342,668, and can be combined with such other photochromic materials. 
The compounds of the present invention may also be combined with other 
photochromic materials such as the naphthopyran compounds described in our 
U.K. Patent Application No. 9306587 or in U.S. Pat. No. 5,066,818. 
Typically, when used in combination, the further additional photochromic 
material is present in an amount of from 0.001 to 0.5 weight %, based on 
the weight of the polymeric host material. 
Examples of suitable uses of the photochromic plastic articles 
incorporating the spiro-oxazine compounds of the invention are in the 
manufacture of plano lenses, e.g. for sunglasses, and ophthalmic lenses 
and as photochromic transparencies for vehicles such as cars and aircraft. 
The spirooxazine materials of the present invention may be prepared by a 
general preparative method which is based on the following reaction 
scheme: 
##STR9## 
In reaction scheme A, an appropriately substituted 
4-amino-1-nitroso-2-hydroxy compound (IV) is condensed with an 
appropriately substituted 2-alkylidene indole compound (V)--also referred 
to hereinbelow as a Fischer base analogue--to produce the spiro (indolino) 
oxazine compounds (I) of the present invention. This condensation reaction 
is analogous to the condensation reaction between nitrosonaphthols and 
2-alkylidene indoles described in detail in, for example, "Photochromism: 
Molecules and Systems", edited by H. Durr and H. Bouas-Laurent, Studies in 
Organic Chemistry 40, Elsevier, 1990--see Chapter 10, and also in various 
patents such as EP 0245020 and U.S. Pat. No. 4,986,934. 
The starting materials of formula (III) in reaction scheme A are believed 
to be new. The synthesis of these starting materials is based on the work 
of W. Brackman and E. Havinga, Recueil, 1955, 74, 937, 1021, 1071 and 
1101. Their work details the synthesis of 4-amino-1,2-naphthaquinone from 
the readily available 2-naphthol. The initial reaction is the oxidation of 
the naphthol by gaseous oxygen and a catalytic quantity of copper (II) 
salt-amine complex (the complex is formed in situ by the simple addition 
of the copper (II) salt to the amine solution). The naphthoquinone formed 
in situ immediately reacts with the amine to form the amino naphthenediol 
which itself is immediately oxidised to form an amino-naphthoquinone 
product in good yield. 
By analogy, the compounds of formula (III) are made using the same reaction 
sequence, as illustrated in Scheme B. 
##STR10## 
By heating the compound of formula (III) with hydroxylamine hydrochloride 
under reflux, one obtains the compounds of formula (IV). 
The starting materials of formula (V), i.e. the Fischer base analogues, are 
made by different methods, depending on the complexity of their 
structures. The synthesis of the simpler Fischer base analogues is well 
known and reported in the literature, see, for example, B. Robinson, The 
Fischer Indole Synthesis, Wiley-Interscience, 1982. Preparation of Fischer 
base analogues having a more complex structure, e.g. having N-branched 
alkyl substituents (e.g. N-neopentyl) or having a ring A which 
is-heterocyclic, is described in more detail in our U.K. Patent 
Application No. 9225347 or in Comprehensive Heterocyclic Chemistry, edited 
by A. R. Katritzky and C. W. Rees, Pergamon 1984, Vol 3, chapter 3.09, p. 
497 et. seq. and in the papers by G. E. Ficken and J. D. Kendall, in J. 
Chem. Soc, 1959, 3203 and J. Chem. Soc., 1961, 584.

The following Examples illustrate the present invention. The structures of 
the various products were determined using n.m.r. and i.r. spectra. 
EXAMPLE 1 
1,3,3-Trimethyl-6'-piperidinospiro2H-indole 
2,3'-3H!-2H-1,4!benzoxazino6,5-b!benzofuran!!. 
Oxygen was bubbled, at a fast rate, for 3 hours, through a vigourously 
stirred solution of 2-hydroxydibenzofuran (73.8 g; 0.40 mol), copper (II) 
acetate (4.60 g; 0.025 mol) and piperidine (79.9 g; 0.94 mol) in methanol 
(600 ml) at room temperature. The resulting dark reaction mixture was 
filtered and the collected solid dried in air to give 
4-piperidinodibenzofuran-1,2-dione as a very dark blue solid (66.3 g; 
59%), m.pt. 151.degree.-6.degree. C. 
##STR11## 
4-Piperidinodibenzofuran-1,2-dione (18.4; 0.062 mol) was added in one 
portion to a vigorously stirred solution of hydroxylamine hydrochloride 
(22.9 g; 0.33 mol) and piperidine (28 g; 0.33 mol) in methanol (230 ml) at 
room temperature. After 1.75 hours the mixture was filtered and the 
resulting solid washed with water and dried to yield 
2-hydroxy-1-nitroso-4-piperidinodibenzofuran as a red-brown solid (3.48 g; 
19%), m.pt. 181.degree.-185.degree. C. (decomp 207.degree. C.). 
##STR12## 
A mixture of 1,3,3-trimethyl-2-methyleneindoline (0.435 g; 0.0025 mol) and 
2-hydroxy-1-nitroso-4-piperidinodibenzofuran (0.675 g; 0.0025 mol) in 
methanol (25.0 ml) was heated under nitrogen and refluxed with stirring 
for 41 hours. The solution was evaporated to dryness and chromatographed 
over silica (eluent: dichloromethane) to yield 
1,3,3-trimethyl-6'-piperidinospiro2H-indole 
2,3'-3H!-2H-1,4!benzoxazino 6,5-b!benzofuran!! as an amber oil (0.35 
g; 32%), which afforded a pale yellow solid upon trituration with diethyl 
ether, m.pt. 213.5.degree.-216.degree. C.; .lambda..sub.max Absorbance 570 
nm (Polyurethane). 
##STR13## 
EXAMPLE 2 
5-Trifluoromethyl-1,3,3-trimethyl-6'-piperidinospiro2H-pyrrolo 
2,3-b!pyridine-2,3'-3H!-2H-1,4!benzoxazino6,5-b!benzofuran!!. 
(a) 2-Chloro-5-trifluoromethylpyridine (44.3 g; 0.24 mol) was treated with 
several portions of methyl hydrazine (33.9 g; 0.74 mol) at room 
temperature under nitrogen. The mixture was heated at 90.degree. C. for 6 
hr. The resulting solid was treated with 3M aqueous NaOH and extracted 
with ethyl acetate. The organic extracts were dried and evaporated to 
leave an oil/solid. Distillation of the crude product to remove excess 
hydrazine gave 1-5-trifluoromethylpyrid-2-yl!-1-methyl hydrazine as a 
white solid (44.0 g; 94%), m.pt. 52.degree.-55.degree. C. 
##STR14## 
(b) A solution of 1-5-trifluoromethylpyrid-2-yl!-1-methyl hydrazine (5.9 
g; 0.031 mol), 3-methyl-2-butanone (5.6 g; 0.065 mol) and 
p-toluenesulphonic acid (0.1 g) in xylene (30 ml) was heated under reflux, 
with water removal (azeotrope), for 7 h. The solution was concentrated to 
yield an oil which was purified by distillation (70.degree. C./72 mbar) to 
yield 3-methyl-2-butanone 1-5-trifluoromethylpyrid-2-yl!-1-methyl 
hydrazone as a yellow oil (5.8 g; 72%). 
##STR15## 
(c) 3-Methyl-2-butanone 1-5-trifluoromethylpyrid-2-yl!-1-methyl hydrazone 
(49.5 g; 0.19 mol) was heated to 250.degree. C. for 3 h. to yield a dark 
oil. Purification by flash-chromatography over silica (eluent: petroleum 
ether 60.80) afforded 5-trifluoromethyl-1,3,3-trimethyl-2-methylenepyrrolo 
2,3-b!pyridine as an orange oil (11.0 g; 24%). 
##STR16## 
(d) A mixture of 
5-fluoromethyl-1,3,3-trimethyl-2-methylenepyrrolo2,3-b!pyridine (17.80 g; 
0.074 mol) and 2-hydroxy-1-nitroso-4-piperidinodibenzofuran (24.1 g; 0.081 
mol) in xylene (50 ml) was stirred and heated under nitrogen and refluxed 
for 24 hours. The solution was evaporated to dryness and the resulting gum 
chromatographed over silica (eluent: 5% diethyl ether in hexane) to give 
5-trifluoromethyl-1,3,3-trimethyl-6'-piperidinospiro2H-pyrrolo2,3-b!pyri 
dine-2,3'-3H!-2H-1,4!benzoxazino6,5-b!benzofuran!! as a red gum which 
afforded a pale yellow solid (2.35 g; 6.1%) after trituration with hexane, 
m.pt. 254.degree.-6.degree. C., .lambda..sub.max Absorbance 506 nm 
(polyurethane). 
##STR17## 
EXAMPLES 3 to 5 
Using preparative procedures analogous to that described in Example 1, the 
following spiro (indolino) oxazines in accordance with the invention were 
also prepared: 
EXAMPLE 3 
5-Methoxy-1,3,3-trimethyl-6'-piperidinospiro2H-indole 
2,3'-3H!-2H-4!benzoxazino6,5-b!benzofuran!! 
##STR18## 
The structure of this compound was elucidated using spectroscopic methods 
(n.m.r. and i.r.). It had a m.pt. of 194.degree.-200.degree. C., and 
.lambda..sub.max absorbance of 598 nm (polyurethane). 
EXAMPLE 4 
1,3,3-Trimethyl-6'-piperidinospiro2H-pyrrolo2,3-b!pyrazine-6,3'-3H!-2H- 
1,4!benzoxazino6,5-b!benzofuran!! 
##STR19## 
The structure of this compound was elucidated using spectroscopic methods 
(n.m.r. and i.r.). It had a m.pt. of 151.degree.-161.degree. C., and 
.lambda..sub.max absorbance of 510 nm (polyurethane). 
EXAMPLE 5 
3,3-Dimethyl-1-neopentyl-6'-pipidinospiro2H-indole 
2,3'-3H!-2H-1,4!benzoxazino6,5-b!benzofuran!! 
##STR20## 
The structure of this compound was elucidated using spectroscopic methods 
(n.m.r. and i.r.). It had a m.pt. of 167.degree.-173.degree. C., and 
.lambda..sub.max absorbance of 588 nm (polyurethane). 
EXAMPLE 6 
6-Trifluoromethyl-1,3,3-trimethyl-6'-piperidinospiro2H-pyrrolo 
2,3-b!pyridine-2,3'-3H!-2H-1,4!benzoxazino6,5-b!benzofuran!! 
(a) 2-Chloro-6-trifluoromethylpyridine (29.28 g; 0.16 mol) was treated with 
several portions of methyl hydrazine (7.9 g; 0.17 mol) and stirred under 
nitrogen at room temperature for 24 h. The mixture was treated with 5M 
aqueous NaOH to basify (pHil) and extracted with ethyl acetate. The 
organic extracts were dried and evaporated to leave an oil (30.12 g) which 
was flash-chromatographed over silica (eluent: 33% diethyl ether in 
hexane) to afford 1-6-trifluoromethylpyrid-2-yl!-1-methyl hydrazine as a 
yellow oil (12.12 g; 38%). 
##STR21## 
(b) A solution of 1-6-trifluoromethylpyrid-2-yl!-1-methyl hydrazine (12.12 
g; 0.069 mol), 3-methyl-2-butanone (5.96 g; 0.069 mol) and 
p-toluenesulphonic acid (0.13 g) in toluene (70 ml) was heated under 
reflux, with water removal (azeotrope), for 24 h. The solution was 
concentrated to yield an oil which was purified by flash-chromatography 
over silica (eluent: 20% diethyl ether in hexane) to yield 
3-methyl-2-butanone 1-6-trifluoromethylpyrid-2-yl!-1-methyl hydrazone as 
an orange oil (11.6 g; 71%). 
##STR22## 
(c) 3-Methyl-2-butanone 1-6-trifluoromethylpyrid-2-yl!-1-methyl hydrazone 
(11.45 g; 0.044 mol) was heated to 250.degree. C. for 15 h. to yield a 
dark oil/gum. Flash-chromatography over silica (eluent: 20% diethyl ether 
in petroleum ether 60.80) afforded 
6-trifluoromethyl-1,3,3-trimethyl-2-methylenepyrrolo2,3-b!pyridine as a 
dark orange oil (6.2 g;58%). 
##STR23## 
(d) A mixture of 
6-trifluoromethyl-1,3,3-trimethyl-2-methylenepyrrolo2,3-b!pyridine (1.45 
g; 0.006 mol) and 2-hydroxy-1-nitroso-4-piperidinodibenzofuran (2.0 g; 
0.0066 mol) in xylene (60 ml) was stirred and heated under nitrogen and 
refluxed for 24 hours. The solution was evaporated to dryness and the 
resulting gum chromatographed over silica (eluent: 20% diethyl ether in 
hexane) to give 
6-trifluoromethyll-1,3,3-trimethyl-6'-piperidinospiro2H-pyrrolo2,3-b!pyr 
idine-2,3'-3H!-2H-1,4!benzoxazino6,5-b!benzofuran!! as an orange solid 
(0.13 g; 4%), m.pt. 221.degree.-5.degree. C., .lambda..sub.max absorbance 
506 nm (polyurethane). 
##STR24## 
EXAMPLE 7 
4,6-Bis(trifluoromethyl)-1,3,3-trimethyl-6'-pipidinospiro 
2H-pyrrolo2,3-b!pyridine-2,3'-3H!-2H-1,4!benzoxazino6,5-b!benzofuran 
!! 
(a) 2-Chloro-4,6-bis(trifluoromethyl)pyridine (19.4 g; 0.078 mol) was 
treated with several portions of methyl hydrazine (4.2 g; 0.090 mol) and 
stirred under nitrogen at room temperature for 24 h. The oil/solid mixture 
was treated with 5M aqueous NaOH to basify (pHil) and extracted with ethyl 
acetate. The organic extracts were dried and evaporated to afford 
1-4,6-bistrifluoromethyl!pyrid-2-yl!-1-methyl hydrazine as an oil (18.4 
g; 91%). 
##STR25## 
(b) A solution of 1-4,6-bistrifluoromethyl!pyrid-2-yl!-1-methyl hydrazine 
(40.04 g; 0.15 mol), 3-methyl-2-butanone (14.2 g; 0.165 mol) and 
p-toluenesulphonic acid (0.32 g) in toluene (90 ml) was heated under 
reflux, with water removal (azeotrope), for 40 h. The solution was 
concentrated to yield a dark oil which was purified by 
flash-chromatography over silica (eluent: petroleum ether 60/80) to yield 
3-methyl-2-butanone 1-4,6-bistrifluoromethyl!pyrid-2-yl!-1-methyl 
hydrazone as a red oil (10.9 g; 22%). 
##STR26## 
(c) 3-Methyl-2-butanone 1-4,6-bistrifluoromethyl!pyrid-2-yl!-1-methyl 
hydrazone (109 g; 0.033 mol) was heated to 245.degree. C. for 15 h. to 
yield a dark oil. Flash-chromatography over silica (eluent: 4% diethyl 
ether in petroleum ether 60/80) afforded 
4,6-bistrifluoromethyl!1,3,3-trimethyl-2-methylenepyrrolo2,3-b!pyridine 
as a low melting brown solid (3.3 g; 32%). 
##STR27## 
(d) A mixture of 
4,6-bistrifluoromethyl!-1,3,3-trimethyl-2-methylenepyrrolo2,3-b!pyridine 
(1.83 g; 0.0059 mol) and 2-hydroxy-1-nitroso-4-piperidinodibenzofuran 
(2.60 g; 0.01 mol) in xylene (50 ml) was stirred and heated under nitrogen 
and refluxed for 24 hours. A further portion of 
2-hydroxy-1-nitroso-4-piperidinodibenzofuran (1.2 g; 0.0059 mol) was added 
and the reaction continued for a further 24 h. The resulting dark solution 
was evaporated to dryness and the resulting gum chromatographed over 
silica (eluent: 2% diethyl ether in petroleum ether 60/80) to give 
4,6-bistrifluoromethyl!-1,3,3-trimethyl-6'-piperidinospiro2H-pyrrolo2,3 
-b!pyridine-2,3'-3H!-2H-1,4!benzoxazino6,5-b!benzofuran!! as an orange 
solid (0.08 g; 3%), m.pt. 195.degree.-205.degree. C., .lambda..sub.max 
absorbance 498 nm (polyurethane). 
##STR28## 
COMATIVE EXAMPLE 1 
1,3,3-Trimethylspiro2H-indole-2,31-3H-naphth2,1-b!1,4!oxazine!. 
A mixture of 1,3,3-trimethyl-2-methyleneindoline (3.62 g; 0.021 mol) and 
1-nitroso-naphthol (3.46 g; 0.02 mol) in ethanol (80.0 ml) was heated 
under reflux for 2 h. The solution was evaporated and the residue 
flash-chromatographed over silica (eluent: dichloromethane) to give 
1,3,3-trimethylspiro2H-indole-2,3'-3H-naphth2,1-b!1,4!oxazine! as a 
pale yellow solid (3.96 g; 60%), m.pt. 127.degree.-130.degree. C. 
##STR29## 
The photochromic properties of the spiro-indolino oxazine compounds of the 
present invention were tested by preparing, in conventional manner, by a 
direct casting process, 1.0 mm plates of a polyurethane host material of 
the type described in EP 0294056 incorporating the photochromic 
spiro-oxazine in a concentration of 0.25% w/w. 
The resultant plates were illuminated under standard solar simulation 
conditions at Air Mass 2.degree. at 21.degree. C. (see Parry Moon, J. 
Franklin Inst. 230, (1940), p 583-617). The measurements which were made 
on the samples in the darkened condition were taken when the samples had 
reached a steady state; this steady state was deemed to have been reached 
after 10 minutes in the darkened condition. 
The results obtained are set out in Table 1. The relatively high IOD values 
obtained with the spiro (indolino) oxazine compounds of the present 
invention (ranging from 0.34 to 1.08) demonstrate the dense colouring 
which is obtained with the photochromic materials of the present 
invention. These results contrast markedly with the low IOD values 
obtained with the comparative sample (0.27). A more proper comparison is 
between Example 1 (IOD of 0.61) and the Comparative Example (IOD of 0.27). 
The photochromic compounds of the present invention are also found, in 
general, to exhibit good fatigue resistance, that is to say that the 
compounds of the present invention are found, in general, to be capable of 
maintaining their good photochro-mic properties and intense dark 
colouration in the darkened state over relatively long periods of time 
without undergoing any substantial degree of degradation. 
TABLE 1 
______________________________________ 
Comparative Test (0.25 w/w % in Polyurethane) 
Bleached 
Darkened Induced Optical 
Transmission 
Transmission 
Darkening .lambda.max 
IVT IVT IVT nm 
______________________________________ 
Example 
1 88.8 21.8 0.61 570 
2 86.8 33.0 0.42 506 
3 87.4 40.0 0.34 598 
4 83.6 17.1 0.69 510 
5 89.9 7.4 1.08 588 
6 89.2 23.9 0.57 506 
Comparative 
Example 
1 88.7 47.9 0.27 605 
______________________________________