1,2-Nucleophilic addition of 2-(picolyl)organoboranes to nitrile, aldehyde, ketone, and amide

Abstract

A series of 2-(picolyl)borane molecules were synthesized as products of the reaction between 2-(picolyl)lithium and R₂BOMe (R = ethyl, 9-BBN, phenyl, 9-borafluorenyl). The 2-(picolyl)boranes were dimeric; whereas, monomers coordinated to LiOMe could be isolated when the synthesis was carried out in the presence of TMEDA and THF. The 2-(picolyl)boranes undergo reaction with nitriles, ketones, aldehydes, and amides with apparent 1,2-addition of the B–C(picolyl) bond to the unsaturated bond. Theoretical models reveal the presence of a donor orbital on the 2-(picolyl)borane with significant electron density at the benzylic carbon that we conclude was involved in nucleophilic attack on the electrophilic center of unsaturated organic functional groups.