An efficient, one-pot, regioselective synthesis of 2-aryl/hetaryl-4-methyl-5-acylthiazoles under solvent-free conditions

In this article, we present an efficient, one-pot regioselective approach towards the synthesis of 2-aryl/hetaryl-4-methyl-5-acylthiazoles obtained during the reaction of alpha-bromo-1,3-diketones generated in situ by triturating unsymmetrical 1,3-diketones with N-bromosuccinimide, with various thioamides under solvent-free conditions. This environmentally benign protocol showed large functional group tolerance, resulted in the exclusive formation of a single isomer, out of the two possible regioisomers in admirable yields. The structure of the isomeric thiazole was assigned unambiguously on the basis of multinuclear NMR [(H-1-C-13) HMBC, (H-1-C-13) HMQC, (H-1-N-15) HMBC] and X-ray crystallographic studies. The entire protocol is ecologically desirable as it employs no organic solvent.