Three-component cascade annulation of β-ketothioamides promoted by CF3CH2OH: a regioselective synthesis of tetrasubstituted thiophenes.

A rapid and highly efficient method for the regioselective synthesis of thiophene derivatives has been developed by annulation of β-ketothioamides with arylglyoxals and 5,5-dimethyl-1,3-cyclohexanedione in CF3CH2OH within 15 min. The present synthesis has several desirable features, such as high regioselectivity, a concise one-pot protocol, short reaction time, and easy purification. This methodology provides an alternative approach for easy access to tetrasubstituted thiophenes via a one-pot cascade reaction without other additives.