Oxidations of Alkylbenzenes with Dimethyldioxirane

Abstract

The oxidation of various alkylbenzenes (1-17) with excess dimethyldioxirane (DMDO) in homogeneous acetone solutions has been studied. In general, the benzylic methylene and methine C–H bonds were oxidized to give the corresponding phenones and tertiary benzylic alcohols, respectively, in relatively low yields. Whereas a tert-butyl substituent at the reaction centre leads to very low conversion due to steric hindrance, the presence of additional phenyl groups appears to favour the oxidation in most, but not all cases. Di- and triphenylmethane (4 and 14) were found to be considerably less reactive than cis-decalin. By contrast, the intramolecular competetive oxidation of isobutylbenzene (19) and 1-methyl-4-phenylcyclohexanes (20) reveals that the benzylic C–H bonds are slightly more reactive than the tertiary ones at remote positions.