One electron oxidation of benzyltrialkylsilanes catalysed by lignin peroxidase: comparison with the oxidation induced by chemical oxidants.
Lignin peroxidase catalyses the H(2)O(2)-induced oxidation of 4-methoxybenzyltrimethylsilane by an electron transfer mechanism. The intermediate radical cation undergoes preferentially C(alpha)[bond]H deprotonation to give 4-methoxybenzaldehyde whereas C(alpha)[bond]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 C(alpha)[bond]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)[double bond]O] of the active oxidant, which is an iron-oxo porphyrin radical cation.
Gerini
Maria Francesca
MF
Dipartimento di Chimica, Università La Sapienza and Istituto CNR di Chimica dei Composti Organometallici (ICCOM-CNR), Sezione di Roma, P.le A. Moro 5, 00185 Rome, Italy. francesca.gerini@uniroma1.it
Lanzalunga
Osvaldo
O
D004579:Electron Transport; D006861:Hydrogen Peroxide / Q000378:metabolism; D007700:Kinetics; D016877:Oxidants / Q000737:chemistry*; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism*; D020075:Phanerochaete / Q000201:enzymology; D012821:Silanes / Q000737:chemistry*; D013379:Substrate Specificity
D016877:Oxidants; D012821:Silanes; D006861:Hydrogen Peroxide; D010544:Peroxidases; C042858:lignin peroxidase