A new regiospecific route to 2, 4-disubstituted thiophenes has been developed through Simmon–Smith reaction on β-methylthio-α, β-unsaturated ketones. Extension of the reaction to β-ethyl/benzylthio-α, β-unsaturated ketones also gave the corresponding 2, 4- disubstituted thiophenes in a regiospecific manner. A probable mechanism involving a carbenoid methylene insertion to divalent sulfur followed by intramolecular aldol ...