Type II photoelimination of thiobenzoic acid O-esters; photolysis of optically active O-2-phenylbutyl thiobenzoate

Abstract

U.v. irradiation of O-2-phenylbutyl thiobenzoate (I) gives Norrish type II products [α-ethylstyrene (II) and thiobenzoic acid] in high yields, the quantum efficiency for the decomposition being 0.49. When the optically active thioester (+)-(S)-(I) is photolysed, the recovered starting material retains its original optical purity, which implies that the intermediate 1,4-diradical (III) is so unstable that the reverse γ-hydrogen shift to re-form structure (I) does not take place to an appreciable extent.