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

The degradation of four dimeric lignin model compounds by meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrin iron chloride (TDCSPPFeCl) (2) are reported. 4-Ethoxy-3-methoxyphenylglycerol-beta-guaiacyl ether (3) (a beta-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-methoxyphenyl)-1,3-propandiol (6, a beta-1 dimer) gave 4, 4-methoxybenzaldehyde (7), and 4-methoxy-alpha-hydroxyacetophenone (8) as major products. Side chain oxidation and aromatic ring cleavage reactions were found to occur for the phenylcoumaran (alpha-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.