Simple FeCl 3 -derived iron catalysts are used for the cleavage of β-O-4 linkages in lignin and lignin model compounds. The degradation of the β-O-4 linkages and the resinol structures in both organosolv and kraft lignin was proven by 2D-NMR (HSQC) experiments, and the oxidative depolymerisation of these lignin sources was confirmed by GPC. Key reactive species facilitating this cleavage are methyl radicals generated from H 2 O 2 and DMSO.

A base-catalysed transformation and cleavage of lignin β-O-4 model compounds in dimethyl carbonate is reported. The reaction system consists of readily available bases and inexpensive dimethyl carbonate as a solvent and reagent, affording methoxy benzene or 2-aryloxyvinyl benzene derivatives in good to very good yields. The applicability of the system for the bond cleavage in an organosolv lignin sample was demonstrated.

The depolymerization of kraft lignin with a copper–vanadium hydrotalcite-like catalyst (HTc-Cu-V) and V­(acac)3/Cu­(NO3)2·3H2O mixtures to monomeric aromatic aldehydes and aromatic acids such as vanillin and vanillic acid using molecular oxygen as oxidant is reported. The obtained products correlate to model-based studies with erythro-1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-1,3-propanediol (1a). Kinetic investigations with 1a demonstrate that there is a combined effect of V­(acac)3 together with Cu­(NO3)2·3H2O that enhances the catalytic activity and increases the selectivity and yield for the cleavage products veratric acid and veratraldehyde. Veratric acid is formed through reaction pathways involving either the transient oxidation products 1-(3,4-dimethoxyphenyl)-3-hydroxy-2-(2-methoxyphenoxy)­propan-1-one (2) and 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)­prop-2-en-1-one (5) or through overoxidation of veratraldehyde. The formation of veratraldehyde likely proceeds through C–C bond cleavage involving either a retro-aldol or a single electron transfer mechanism.