Photochemical and enzymatic SET promoted C–C bond cleavage reactions of lignin β-1 model compounds containing varying number of methoxy substituents on their arene rings

In the current study, 1,2-diarylpropan-1,3-diols, containing varying numbers of methoxy substituents that mimic β-1 type units in lignins, were prepared and subjected to photochemical and enzymatic SET oxidative C–C bond cleavage reactions to explore how product distributions and reactivity profiles depend on the numbers and positions of arene ring methoxy-substituents. For this purpose, product distributions of SET-promoted photochemical reactions of the β-1 model compounds and the characteristics of lignin peroxidase catalyzed bond cleavage reactions of these substances were explored. The results show that both the photochemical and enzymatic reactions, which are known to occur by initial SET to form arylpropanoid cation radicals, generate predominantly aldehydes and β-hydroxyketones through cation radical C1–C2 bond cleavage pathways. In addition, analysis of the relative quantum efficiencies of the SET photochemical processes shows that they do not depend greatly on the numbers and positions of arene ring methoxy substituents of the β-1 model compounds.

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