Rhodium-Catalyzed Synthesis of Benzo[b]thiophene-3-Carboxamides via Cyclization of (ortho-Alkynyl)phenyl Sulfides in the Presence of Isocyanates

A facile synthesis of benzo[b]thiophene-3-carboxamides from (ortho-alkynyl)phenyl methoxymethyl sulfides and isocyanates was realized. The method involves a tandem-type, cyclization–addition sequence in the presence of a rhodium catalyst. The reactions proceed under considerably mild conditions (room temperature to 50 °C), providing an efficient and entirely new route to substituted benzo[b]thiophene-3-carboxamide derivatives.