Condensation of thiourea derivatives with carbonyl compounds: one-pot synthesis of N-alkyl-1,3-thiazol-2-amines and of 3-alkyl-1,3-thiazolimines

The reactions of ketones and N-substituted thioureas, in the presence of HCl (or HBr) and DMSO afford mixtures of the title compounds which are easily separated on a silica gel column. This method avoids the classical use of alpha-haloketones. The mechanism of these reactions involves the enolization of ketones and the activation of thiourea sulfur, probably by oxygen transfer from DMSO.