LiBr catalyzed solvent-free ring expansion of epoxides to 1,4-oxathian-2-ones with α-mercaptocarboxylic acids

An efficient and rapid (10-20 min) one-pot synthesis of chemically and pharmaceutically interesting 1,4-oxathian-2-ones is reported. The protocol involves LiBr catalyzed regioselective ring-opening-ring-closing reaction cascade of terminal epoxides with α-mercaptocarboxylic acids at rt under solvent-free conditions. Recycling of the catalyst, atom economy, and formation of water as the only by-product in the present synthesis are additional advantages relevant to green chemistry.