The biomimetic oxidation of β-1, β-0-4, β-5, and biphenyl lignin model compounds by synthetic iron porphyrins

Abstract

The degradation of four dimeric lignin model compounds by meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrin iron chloride (TDCSPPFeCI) ( 2) are reported. 4-Ethoxy-3-methoxyphenylglycerol-β-guaiacyl ether ( 3) (a β-0-4 dimer) was cleaved to give 4-ethoxy-3-methoxybenzaldehyde ( 4) and guaiacol ( 5) as major products. The oxidation of 1-(4-ethoxy-3-methoxyphenyl)-2-(4-metho ( 6, a β-1 dimer) gave 4, 4-methoxybenzaldehyde ( 7), and 4-methoxy-α-hydroxyacetophenone ( 8) as major products. Side chain oxidation and aromatic ring cleavage reactions were found to occur for the phenylcoumaran (α-5) model compound, ethyl dehydrodiisoeugenol ( 12). A biphenyl model compound, 4,4′-diethyldehydrodivanillin ( 20), was oxidized to give mono- and dicarboxy derivatives, as well as ring-cleaved products of the acid derivatives.