A highly chemoselective oxidation of alcohols to carbonyl products with iodosobenzene diacetate mediated by chromium(III)(salen) complexes: synthetic and mechanistic aspects.
[reaction: see text] The catalytic oxidation of the allylic alcohols 1d-n with iodosobenzene diacetate, mediated by the [Cr(III)(salen)]X complex, affords the respective enones in excellent chemoselectivity for Cl(-) as counterion [complex A(Cl)], while for the counterions TfO(-) [complex A(TfO)] and PF(6)(-) [complex A(PF(6)())] nearly equal amounts of enone and epoxide are observed. This counterion-dependent oxidation of allylic alcohols by Cr(III)(salen) complexes is rationalized in terms of Lewis acid catalysis by the complex A(Cl) and redox catalysis for A(TfO) and A(PF(6)()).
Adam
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W
Institut für Organische Chemie and für Lebensmittel Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany. adam@chemie.uni-wuerzburg.de
Hajra
S
S
Herderich
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M
Saha-Möller
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CR