Computational Mechanistic Study of Palladium(II)-Catalyzed Carboxyalkynylation of an Olefin Using an lodine(III) Oxidant Reagent

The Pd(II)-catalyzed chemical transformations using an iodine(III) oxidant are mostly believed to proceed via a Pd(IV)/Pd(II) catalytic cycle. The present computational study, however, demonstrates that this statement is not always true, and, in some particular cases, an alternative mechanism could be operative. Herein, the reaction mechanism of the Pd(II)-catalyzed carboxyalkynylation of an olefin using an alkynyl benziodoxolone reagent was elucidated with the aid of density functional theory calculations. The catalytic reaction was found to proceed via a mechanism in which a Pd(II) vinylidene-like complex, not a Pd(IV) complex, plays a leading role. The mechanistic understanding of the carboxyalkynylation reaction may have significant implications in a variety of processes catalyzed by transition metal complexes in the presence of alkynyl benziodoxolones.