Catalytic C(β)–O Bond Cleavage of Lignin in a One-Step Reaction Enabled by a Spin-Center Shift

Abstract

A challenge to the utilization of lignin as a feedstock for aromatic fine chemicals lies in selective cleavage of copious β-O-4 linkages. A photocatalytic strategy for the selective cleavage of the C(β)–O bonds of model substrates and natural lignin extracts is achieved by a redox-neutral, catalytic cycle that does not require stoichiometric reagents. Mechanistic studies reveal the generation of a thiyl radical, which is derived from a cystine-derived H-atom transfer catalyst, initiates a spin-center shift (SCS) that leads to C(β)–O bond cleavage. The SCS reactivity is reminiscent of the C(β)–O bond cleavage chemistry that occurs in the active site of ribonucleotide reductase.

Topics & Concepts