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.