Mechanism and origins of ligand-controlled regioselectivity of copper-catalyzed borocarbonylation of imines with B2pin2 and alkyl iodides: a computational study

Abstract

Density functional theory calculations have been performed to investigate the copper-catalyzed borocarbonylation of imines with B₂pin₂ and alkyl iodides. The computations reveal that the reaction is initiated by the selective migratory insertion of the C–N double bond into the Cu–B bond to forge the key α-boryl amido-copper complex, which could undergo the 1,2-rearrangment via a stepwise dearomatization–rearomatization pathway to give α-amino alkyl-copper species. From these intermediates, the following C–I bond cleavage of alkyl iodide through halogen-atom abstraction, radical association, and reductive elimination would lead to α-boryl amide and α-amino ketone products. The regioselectivity of the overall reaction is determined by the competition between the 1,2-rearrangement and C–I bond cleavage from the α-boryl amido-copper complex. The experimentally observed ligand-controlled regioselectivity is reproduced very well by the computations, which is rationalized on the basis of Cu⋯O interaction and Cu–N bond strength.