Photoinduced Single Electron Reduction of the 4‐O‐5 Linkage in Lignin Models for C‐P Coupling Catalyzed by Bifunctional N‐Heterocyclic Carbenes

Abstract

Abstract Catalytic activation of Caryl‐O bonds is considered as a powerful strategy for the production of aromatics from lignin. However, due to the high reduction potentials of diaryl ether 4‐O‐5 linkage models, their single electron reduction remains a daunting challenge. This study presents the blue light‐induced bifunctional N‐heterocyclic carbene (NHC)‐catalyzed one‐electron reduction of diaryl ether 4‐O‐5 linkage models for the synthesis of trivalent phosphines. The H‐bond between the newly devised bifunctional NHC and diaryl ethers is responsible for the success of the single electron transfer. Furthermore, this approach demonstrates selective one‐electron reduction of unsymmetric diaryl ethers, oligomeric phenylene oxide, and lignin model.

Keywords

• bifunctional N‐heterocyclic carbenes
• C─O bond activation
• lignin
• one electron reduction
• trivalent phosphines