As a C1 synthetic block, isocyanates were widely used in the synthesis of amide derivatives or heterocyclic compounds. Density functional theory (DFT) calculation was employed to reveal the mechanism of Cu(I)-catalyzed hydroboraethylation of isocyanates. Cu(I)O^tBu was considered as the active species in catalytic cycle. The catalytic cycle involves transmetallation with borane, alkene insertion, isocyanate insertion, and transmetallation with LiO^tBu to yield lithium acetylamide product. The isocyanate insertion was considered as rate-determining step, which underwent a unique three- membered ring type transition state. The catalytic cycle with chiral phosphine ligand was also considered for this reaction. DFT calculation resulted that the enantioselectivity was determined at the alkene insertion step, which was controlled by steric effect of phosphine ligand. Moreover, it was also found that the activation free energy for the rate-determining step with phosphine ligand was lower than that with carbene ligand. Therefore, the phosphine ligand would lead to a higher reaction rate.

Key words: cuprous catalysis, density functional theory (DFT) study, isocyanate, insertion