Electrochemical C–O bond cleavage of diaryl ethers: upcycling of lignin 4-O-5 models and polyphenylene oxide†
Abstract
Selective and efficient cleavage of diaryl ether C–O bonds is significant and challenging for biomass conversion and organic synthesis. Herein, a mild and effective electrochemical method for nucleophilic aromatic substitution (SNAr) of diaryl ethers with various N- and O-nucleophiles is reported. Without the necessity of extra redox reagents and strong bases, this electrochemical SNAr reaction provides a selective and sustainable method for aromatic C–O bond cleavage and functionalization. Preliminary mechanistic studies support an electrooxidative dearomatization of diaryl ether pathway, wherein generation of a quinone imine cation facilitates the subsequent polar nucleophilic aromatic substitution through transient polarity inversion. Specifically, a practical application of this protocol is the efficient upcycling and valorization of lignin 4-O-5 models and polyphenylene oxide into value-added chemicals under ambient electrochemical conditions.