Bifunctional NHC Catalysis Enables Umpolung Photocarbonylation of Two Electrophiles: Access to Unsymmetric Diaryl 1,4-Diketones

Abstract

Unsymmetric diaryl 1,4-diketones are valuable structural motifs in organic synthesis. Direct controlled installation of two distinct aryl-substituted carbonyl groups is conceptually straightforward yet synthetically challenging. Herein we report an example of unsymmetric diaryl 1,4-diketones synthesis via N-heterocyclic carbene enabled umpolung photo-carbonylation.In this system, NHC catalysis induces umpolung while simultaneously generating Breslow intermediates in situ that function as intrinsic photoactive redox mediators for the subsequent photocarbonylation. This bifunctional catalytic design enables photocarbonylation without metals, external photocatalysts, or stoichiometric reductants. The process overcomes the polarity mismatch and enables regioselective carbonylation and acylation, providing a diverse array of unsymmetric diaryl 1,4-diketones with high precision. This strategy establishes a mechanistically distinct and sustainable platform for regioselective umpolung photocarbonylation.