Mechanistic investigation of Cu(I)-mediated three-component domino reaction of asymmetrical alkynes with carbon dioxide: Theoretical rationale for the regioselectivity

A computational study with the Becke3LYP DFT functional theory was carried out on Cu(I)-mediated domino reaction of asymmetrical alkynes with CO2 by the reducing reagent of hydrosilane. We studied the mechanism for the entire reaction and the selectivity-determining step in order to understand the regioselectivity. Coupling of alkyne with LCuH (L = N-heterocyclic carbene) is computed to be the selectivity-determining step, though not the rate-determining step. The steric and electronic factors that determine the regioselectivity have been discussed. The calculations show that the electronic factors are not the sole reason for the observed regioselectivity. The observed regioselectivity is dominated by both electronic factors and steric factors. Furthermore, the computational results are in good agreement with the experimental results.