Merging the Norrish type I reaction and transition metal catalysis: photo- and Rh-promoted borylation of C-C σ-bonds of aryl ketones.

Synthesis of arylboronates via borylation of C-C σ-bonds of aryl ketones was achieved by the combined use of photoenergy and a Rh catalyst. The cooperative system enables α-cleavage of photoexcited ketones to generate aroyl radicals via the Norrish type I reaction, which are successively decarbonylated and borylated with the rhodium catalyst. This work establishes a new catalytic cycle merging the Norrish type I reaction and Rh catalysis and demonstrates the new synthetic utility of aryl ketones as aryl sources for intermolecular arylation reactions.