SE327207

1,136,683. Spiropyrans. NATIONAL CASH REGISTER CO. 21 Feb., 1967 [28 March, 1966], No. 8102/67. Heading C2C. [Also in Divisions B2, C3 and C4] The invention comprises compounds of the formula wherein R 1 is hydrogen and R 2 a phenyl or p-methoxyphenyl group, or R 1 is a methoxy group and R 2 is a methyl or phenyl group. The compounds are prepared by reacting the appropriate coumarin derivative in ether solution with phenylmagnesium bromide, decomposing the reaction product with concentrated HCl and precipitating the corresponding benzopyrylium chloride, reacting this intermediate with 6 - nitro - 2 - hydroxy - 1 - naphthaldehyde in the presence of dry HCl, hydrolysing the resultant naphthavinylpyrylium chloride and crystallizing the required naphthoisospiropyran therefrom. Examples describe the preparation of the four compounds of the above formula. These spiropyrans are photo-chromic compounds and are used in the preparation of light sensitive films (see Divisions B2, C3, C4].