Direct Aroylation of Olefins through a Cobalt/Photoredox-Catalyzed Decarboxylative and Dehydrogenative Coupling with α-Oxo Acids

A photoredox/cobalt dual catalytic procedure has been developed that allows benzoylation of olefins. Here the photoredox catalyst effects the decarboxylation of alpha-ketoacids to form benzoyl radicals. After addition of this radical to styrenes, the cobalt catalyst abstracts a H-atom. Hydrogen evolution from the putative cobalt hydride intermediate allows a Heck-like aroylation without the need for a stoichiometric oxidant. Mechanistic studies reveal that electronically different styrenes lead to a curved Hammett plot, thus suggesting a change in product-determining step in the catalytic mechanism.

Automated summary

A dual catalytic procedure involving photoredox and cobalt catalysts has been developed for the benzoylation of olefins. The photoredox catalyst initiates the decarboxylation of alpha-ketoacids to generate benzoyl radicals, which react with styrenes in the presence of a cobalt catalyst that abstracts a hydrogen atom. The catalytic system allows a Heck-like aroylation without the need for a stoichiometric oxidant. Mechanistic studies show that differently substituted styrenes result in a curved Hammett plot, suggesting a change in the product-determining step in the catalytic mechanism.