Gold-Catalyzed Intermolecular Alkyne Oxyarylation for C3 Functionalization of Benzothiophenes.

C3-selective C-C bond formation on benzothiophenes is challenging, and few direct functionalization methods are available. A gold-catalyzed reaction of alkynes with benzothiophene -oxides provides regioselective entry into C3-alkylated benzothiophenes with the C7-alkylated isomer as the minor product. This oxyarylation reaction works with alkyl and aryl alkynes and substituted and unsubstituted benzothiophenes. Mechanistic studies identify that sulfoxide inhibits the catalyst [DTBPAu(PhCN)]SbF, which also degrades and forms the unreactive complex [(DTBP)Au]SbF.