Importance

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Abstract

A naphthopyran compound of general formula (I) ##STR1## wherein R.sub.1 represents an alkyl group or an aryl group; each of R.sub.4 and R.sub.5, which may be the same or different, independently represents an alkyl, alkenyl, carbocyclic or heterocyclic group, or R.sub.4 and R.sub.5 taken together with the carbon atom to which they are attached form a carbocyclic ring or a heterocyclic ring; and R.sub.6 represents a hydrogen atom or a substituent selected from alkyl, alkoxy, aryl, aryloxy, heteroaryl, halogen, amino, substituted amino, azo, imino, amide, carboxylate, ester, cyano, trifluromethyl or nitro, and in addition R.sub.6 may represent a carbocyciic or heterocyclic ring fused to ring A. The naphthopyran compounds of the invention are useful as photochromic materials in lenses, e.g. sunglasses, and photochromic transparencies for cars and aircraft.

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First Claim