Two-Step, Catalytic C-C Bond Oxidative Cleavage Process Converts Lignin Models and Extracts to Aromatic Acids

We herein report a two-step strategy for oxidative cleavage of lignin C-C bond to aromatic acids and phenols with molecular oxygen as oxidant. In the first step, lignin beta-O-4 alcohol was oxidized to beta-O-4 ketone over a VOSO4/TEMPO [(2,2,6,6-tetramethy1piperidin-1-yl)oxyl)] catalyst. In the second step, the C-C bond of beta-O-4 linkages was selectively cleaved to acids and phenols by oxidation over a Cu/1,10-phenanthroline catalyst. Computational investigations suggested a copper-oxo-bridged dimer was the catalytically active site for hydrogen-abstraction from C-beta-H bond, which was the rate-determining step for the C-C bond cleavage