Light-Driven Ligand Exchange for Palladium-Catalyzed Regiodivergent Transfer Hydrothiocarbonylation

Transfer hydrocarbonylation of alkenes could streamline the synthesis of value-added carbonylated molecules by avoiding the use of pressurized toxic CO. Existing methods, however, are limited to the use of alcohol-derived formates or anhydrides as CO and nucleophile-surrogates, because the parallel mechanism does not work for other transfer carbonylation reagents comprising nucleophilic fragments with higher coordination affinities to transition metals. Herein, we present a novel visible-light-driven strategy to address this challenge by promoting the ligand exchange via facilitating the dissociation of CO instead of nucleophiles, upon which was also an efficient transfer hydrothiocarbonylation of olefins with thioformates successfully established. The protocol features mild reaction conditions, excellent regioselectivities, broad functional group compatibilities, and vital synthetic efficacy. The kinetic analysis unveiled a striking linear correlation between the product concentration and the time-squared. Furthermore, the kinetic behaviors observed for the substrates were all consistent with the rate law derived from the proposed mechanism. These results demonstrated the pivotal importance of rapid CO dissociation via light excitation to suppress the side reaction of premature reductive elimination.