Highly Efficient and Stereoselective Thioallylation of Alkynes: Possible Gold Redox Catalysis with No Need for a Strong Oxidant

Stereoselective thioallylation of alkynes under possible gold redox catalysis was accomplished with high efficiency (as low as 0.1% catalyst loading, up to 99% yield) and broad substrate scope (various alkynes, inter-and intramolecular fashion). The gold(I) catalyst acts as both a p-acid for alkyne activation and a redox catalyst for AuI/III coupling, whereas the sulfonium cation generated in situ functions as a mild oxidant. This novel methodology provides an exciting system for gold redox catalysis without the need for a strong oxidant.