Visible Light Induced B–H Bond Insertion Reaction with Diazo Compounds

A protocol induced by visible light for the direct insertion of α-carbonyl carbenes into the B–H bond of amine-borane adducts has been developed under conditions that are free of metal and photocatalyst. This approach provides a straightforward route to various organoboron compounds from diazo compounds and amine-borane adducts with moderate to good yields. Mechanistic investigations reveal that this photoinduced reaction proceeds through concerted carbene insertion into the B–H bond, and the photoinduced generation of free carbene from α-diazo esters may be the rate-determining step.