Pd-Catalyzed Synthesis of Benzothiophenes from gem-Dihalovinyl Thiophenols

Significance

Based on an analogous synthesis of 2-substituted indoles from gem-dihalovinyl anilines (Y.-Q. Fang, M. Lautens J. Org. Chem. 2007, 73, 538), the preparation of 2-substituted benzothiophenes from gem-dihalovinyl thiophenols under Pd catalysis is described. The reaction involves an intramolecular S-vinylation and an intermolecular C-C bond formation. The majority of the examples are given for the Suzuki-Miyaura reaction for which PdCl₂/S-Phos as a catalytic system and K₃PO₄/Et₃N as combination of bases were found to be the optimized conditions compatible with a variety of different boron reagents. Four examples of Heck and Sonogashira cross-coupling reactions in tandem with the C-S coupling were also presented as an extension of the reaction.