Co(salen) catalysed oxidation of synthetic lignin-like polymer: Co(salen) effects

In this paper, Co(salen) [salen = N, N’-bis(salicylidene)ethylenediamine] complex was studied as oxygen activators for the catalytic oxidation of a lignin model polymer using water as the solvent, with molecular oxygen and hydrogen peroxide as the oxidants. The effect of Co(salen) on oxidation was tested by spectroscopic methods (FTIR, 13C-NMR and GC-MS). The reactions catalysed by Co(salen) included Cα-alcohol oxidation, Cα-Cβ side chain cleavage, demethoxylation, aromatic ring cleavage, and β-O-4 cleavage. In addition to the mechanistic information obtained, the effect of Co(salen) suggests that Co(salen) can be important for the catalytic oxidation, as they affect the oxidation of lignin model polymer. The reaction performed in the presence of Co(salen) was more efficient than without it. The formation of aldehyde in the catalytic oxidation, as shown by GC-MS, could be identified as the mechanism of oxidative cleavage of the β-O-4 bonds.