Attempted Simmons-Smith reaction on α-oxoketene dithioacetals: A new general route to 3,4-substituted and annelated thiopenes

Article abstract of DOI:10.1016/S0040-4020(01)88342-3

A new general synthesis of 3- and 3,4-substituted 4a-q, 3,4-annelated 7a-d and condensed tricyclic 9a-e thiophenes has been developed through Simmons-Smith reaction of the respective α-oxoketene dithioacetals. Extension of the reaction of α-cinnamoylketene dithioacetals 10a-e and its higher enyl analogs 13a-d, 15a-c gave the corresponding 3-styryl 11a-e and 3-di- and trienyl 14a-d, 16a-c thiophenes in highly regioselective manner. A probable mechanism involving an unusual intramolecular aldol condensation of sulphonium ylid formed through carbenoid methylene insertion on divalent sulfur has been suggested.