Addition reactions of heterocyclic compounds. Part 74. Products from dimethyl acetylenedicarboxylate with thiourea, thioamide, and guanidine derivatives

Abstract

Benzimidazole-2-thione with dimethyl acetylenedicarboxylate (DMAD) in acetonitrile gave a fused thiazolidinone derivative, but in methanol a fused thiazinone was obtained. Structures were assigned to adducts from other thioureas by comparison with the ¹³C n.m.r. spectra for these compounds. A method has been developed for distinguishing between the possible structural types of adducts for guanidine and amidine derivatives with DMAD using ¹H and ¹³C n.m.r. spectroscopy. Products from various thioamides and DMAD were identified from their n.m.r. and other spectra.