Visible Light Induced\nB–H Bond Insertion Reaction\nwith Diazo Compounds

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