Mechanistic studies in the chemistry of thiourea. Part 2. Reaction with benzil in acid solution

Abstract

Benzil reacts with 1,3-dimethylthiourea, 1-methylthiourea, and thiourea in acid solution to give 4,5-diphenyl-4-imidazolines (3) which, in the cases of 1-methylthiourea and thiourea, readily form disulphides 11. Another product of reaction is a bicyclic compound 4 in which it appears that in one thiourea moiety sulphur has been replaced by oxygen. A mechanistic pathway for the formation of 3 and 4 is proposed involving thiourea acting as a sulphur nucleophile, urea as a leaving group, and the thermal decomposition of thiiranes.