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One Electron Oxidation of α‐Alkylbenzyl Alcohols Induced by Potassium 12‐Tungstocobalt(III)ate − Comparison with the Oxidation Promoted by Microsomal Cytochrome P450
Author(s) -
Baciocchi Enrico,
Belvedere Sandro,
Bietti Massimo,
Lanzalunga Osvaldo
Publication year - 1998
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(199802)1998:2<299::aid-ejoc299>3.0.co;2-b
Subject(s) - chemistry , bond cleavage , microsome , medicinal chemistry , electron transfer , ketone , stereochemistry , alkyl , potassium , cleavage (geology) , fragmentation (computing) , photochemistry , enzyme , organic chemistry , catalysis , operating system , geotechnical engineering , fracture (geology) , computer science , engineering
The chemical and microsomal oxidations of a number of 4‐methoxy substituted α‐alkylbenzyl alcohols 4‐MeOPhCH(R)OH ( E ox = 1.6−1.7 V vs SCE) were investigated. Using potassium 12‐tungstocobalt(III)ate, a bona fide one electron oxidant, competition between C α −H and C α −C β bond cleavage in the intermediate radical cation was observed when the side‐chain alkyl group R was Et ( 2 ) and i Pr ( 3 ). With R = Me ( 1 ), only C−H bond cleavage took place, whereas with R = t Bu ( 4 ) C−C bond cleavage was the exclusive fragmentation process. In contrast, the microsomal oxidation of the two substrates 3 and 4 led in both cases to the exclusive formation of the corresponding ketone. Thus, an electron transfer mechanism appears unlikely for the microsomal oxidation of α‐alkylbenzyl alcohols, even though the oxidation potential of these species is lower than or comparable to that of the active oxidant in the enzyme. A hydrogen atom transfer mechanism is more in line with these results.