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 β-O-4 alcohol was
oxidized to β-O-4 ketone over a VOSO4/TEMPO [(2,2,6,6-tetramethylpiperidin-1-yl)oxyl)]
catalyst. In the second step, the C–C bond of β-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
Cβ–H bond, which was the rate-determining
step for the C–C bond cleavage.