Synthesis of benzothiophenes via sulfonium-[3,3]-rearrangement of aryl sulfoxides with allenenitriles

Abstract

A general one-pot, two-step synthesis of benzothiophenes is presented. First, the Morita–Baylis–Hillman (MBH) type sulfonium-[3,3]-rearrangement of aryl sulfoxides with allenenitriles generates ortho-allenic phenyl sulfides, which then undergo in situ cyclization/isomerization to give 2-alkyl-3-cyano-benzothiophenes. The reaction features mild reaction conditions, excellent functional-group compatibility and broad substrate scope. Therefore, a diverse range of 2-alkyl 3-cyano-benzothiophenes have been prepared from a wide variety of readily available aryl sulfoxides and allenenitriles.