Mechanistic studies in the chemistry of thiourea. Part 1. Reaction with benzil under alkaline conditions

Abstract

Benzil reacts under alkaline conditions with 1,3-dimethylthiourea to form 4,5-dihydroxy-1,3-dimethyl-4,5-diphenyltetrahydroimidazole-2-thione (1); with 1-methylthiourea to form 3-methyl-5,5-diphenyl-2-thiohydantoin (9); and with thiourea to form both the corresponding hydantoin and 3a,7a-diphenyltetrahydroimidazo[4,5-d]imidazole-2,5-dithione (19). The use of high field n.m.r. spectroscopy and benzil labelled with carbon-13 in the carbonyl group has permitted delineation of the reaction mechanisms and detection of a number of transient intermediates.