Au(I) as a π‑Lewis Base Catalyst: Controlled Synthesis of Sterically Congested Bis(triflyl)enals from α‑Allenols

A gold-catalyzed bis­[(trifluoromethyl)­sulfonyl]­ethylation of α-allenols, which allows the preparation of sterically congested bis­(triflyl)­enals bearing quaternary carbon centers, is presented. This sequence differs from the conventional reaction pathway of α-allenols under π-acid catalysis, because in our case Au­(I) functions as a π-Lewis base catalyst rather than a π-Lewis acid to activate the allene, facilitating the unusual addition of a carbon nucleophile of the gold complex belonging to the allenol moiety. Density functional theory calculations were carried out to understand this uncommon pathway.