Exploring the mechanism of Ni-catalyzed four-component carbonylation of alkenes and ethers using density functional theory

Abstract

This study employs density functional theory (DFT) calculations to thoroughly dissect the mechanistic intricacies of the nickel-catalyzed four-component carbonylation involving alkenes and ethers. The computational results reveal that active species in this catalytic system is Ni(I), which triggers the onset of the catalytic cycle. Interestingly, the detailed sequence of elementary steps identified here diverges from the experimental mechanistic proposals. The overall mechanism follows a Ni^I/Ni^II/Ni^III/Ni^I catalytic cycle, where the rate-limiting step is the THF radical addition to ethylene. The key challenge of multicomponent reactions lies in the complexity of their reaction mechanisms. To address this, we investigated the reaction using 5-hexenol, a substrate that contains both a double bond and a hydroxyl group. The findings indicate that steric hindrance is a key factor in dictating whether ethylene or the double bond in 5-hexenol engages in the reaction. Further analysis reveals that different alcohol substrates significantly influence reaction efficiency. Computational data indicate a correlation between CO insertion barriers and experimental yields, where increased steric bulk and electron donation at the Ni center raise energy barriers, thereby lowering the overall reaction yield. These findings offer insight into how alcohol structure modulates catalytic performance, guiding future reaction optimization.