Gold-Catalyzed Oxidation Reactions of Thioalkynes with Quinoline N-Oxides: A DFT Study.

ABSTRACT

Mechanistic investigation of the gold-catalyzed oxidative reactions of thioalkynes with quinoline N-oxides was performed using density functional theory (DFT) calculations. For the oxidative rearrangement of thioalkynes with quinoline N-oxide to yield the same products, the Cß-oxidation of thioalkynes was predicted to be competitive with Cα-oxidation, with the Cß-oxidative process slightly more favorable. However, for the oxidative alkenylation of propargyl aryl thioethers with quinoline N-oxides, the Cß-oxidation of thioether by quinoline N-oxide generated the product 3-hydroxy-1-alkylidene phenylthiopropan-2-one. Moreover, the ring opening of the four-membered sulfonium intermediate was achieved by the nucleophilic attack of quinoline N-oxide rather than a water molecule.