One electron oxidation of benzyltrialkylsilanes catalysed by lignin peroxidase: comparison with the oxidation induced by chemical oxidants

Lignin peroxidase catalyses the H2O2-induced oxidation of 4-methoxybenzyltrimethylsilane by an electron transfer mechanism.
The intermediate radical cation undergoes preferentially Ca–H deprotonation to give 4-methoxybenzaldehyde whereas Ca–Si bond
cleavage is a minor fragmentation pathway and leads to 4-methoxybenzyl alcohol. Similar results are obtained in the oxidation
catalysed by the water soluble model compound 5,10,15,20-tetra(N-methyl-4-pyridyl)porphyrinatoiron(III) pentachloride. Instead,
in the oxidation promoted by the genuine one-electron transfer oxidant potassium dodecatungstocobalt(III)ate Ca–Si bond cleavage
is the exclusive fragmentation process of the intermediate radical cation. It is suggested that in the enzymatic and biomimetic
oxidations of 4-methoxybenzyltrimethylsilane the deprotonation of the intermediate radical cation is promoted by the reduced form
[PorFe+.(IV)=O] of the active oxidant, which is an iron-oxo porphyrin radical cation.