Photocatalytic, Oxidative Cleavage of C−C Bond in Lignin Models and Native Lignin

Abstract

It is challenging to realize the selective C−C bond cleavage of lignin β-O-4 linkages for production of high-value aromatic chemicals due to its intrinsic inertness and complex structure. Here we report a light-driven, chlorine-radical-based protocol to realize the oxidative C−C bond cleavage in various lignin model compounds catalyzed by commercially available TPT and CaCl2, achieving high conversion and good to high product yields at room temperature. Mechanistic studies reveal that the preferential activation of Cβ−H bond facilitates the oxidation and C−C bond cleavage of lignin β-O-4 model via chlorine radical. Furthermore, this method is also applicable to the depolymerization of natural lignin extracts, furnishing the aromatic oxygenates from the cleavage of Cα−Cβ bonds. This study provides experimental foundations to the depolymerization and valorization of lignin into high value-added aromatic compounds.