How does methanol assist the hydrogen transfer in Pd-catalyzed cyclocarbonylation of allylic alcohols? insights from a DFT study

The carbonylation mechanisms of allylic alcohol catalyzed by [PdHCl(bppm)] complex were studied using a density functional theory (DFT) method. The results indicate that the catalytic cycle consists of three main steps: alkene insertion, CO insertion, and hydrogen transfer and product elimination. Pathways with a Pd(II) character are more favorable than that with Pd(IV) character. Methanol serves as the proton shuttle in carbonylation and reduces the energy barrier by 15.4 kcal mol1 below that without methanol assistance.