Metal-Free sigma-Bond Metathesis in 1,3,2-Diazaphospholene-Catalyzed Hydroboration of Carbonyl Compounds

摘要

The first metal-free catalytic hydroboration of carbonyl derivatives has been developed in which a catalytic amount of 1,3,2-diazaphospholene effectively promotes a hydroboration reaction of aliphatic and aromatic aldehydes and ketones. The reaction mechanism involves the cleavage of both the PO bond of the alkoxyphosphine intermediate and the BH bond of pinacolborane as well as the formation of PH and BO bonds. Thus, the reaction proceeds through a non-metal sigma-bond metathesis. Kinetic and computational studies suggest that the sigma-bond metathesis occurred in a stepwise but nearly concerted manner.