Understanding the Higher Reactivity of B2cat2versus B2pin2in Copper(I)-Catalyzed Alkene Diboration Reactions

DFT calculations have been carried out to study the reactivity difference of B2cat2 and B2pin2 in the diboration reaction of alkenes catalyzed by carbene-ligated copper(I) complexes. The higher reactivity of B2cat2 versus B2pin2 in this reaction results largely from the enhanced electrophilicity/Lewis acidity of the former, which significantly lowers the barrier in the product-forming transmetalation step. Transmetalation reactions of B2cat2 and B2pin2 with (NHC)Cu−OMe have also been investigated, and the relative barriers are much closer than with analogous Cu−R systems.