Mechanistic Studies on N-Heterocyclic Carbene-Catalyzed Umpolung of β,γ-Unsaturated α-Diketones

The mechanism of N-heterocyclic carbene-catalyzed umpolung of beta,gamma-unsaturated alpha-diketone was studied using both density functional theory (DFT) calculations and experimental methods. In contrast to the originally proposed mechanism, the calculations revealed a more complicated process involving both nucleophilic O-acylated homoenolate and electrophilic alpha,beta-unsaturated acyl azolium intermediates. The experimental studies confirmed the existence of the aforementioned two key intermediates. A revised mechanism has been proposed to demonstrate the detailed mechanistic insights into the product formation.

Automated summary

The mechanism of N-heterocyclic carbene-catalyzed umpolung of beta,gamma-unsaturated alpha-diketone was found to be more complicated than originally proposed, involving nucleophilic O-acylated homoenolate and electrophilic alpha,beta-unsaturated acyl azolium intermediates. Both DFT calculations and experimental studies confirmed the existence of these key intermediates, leading to a revised mechanism for product formation.