ALKANE OXIDATION WITH MOLECULAR-OXYGEN USING A NEW EFFICIENT CATALYTIC-SYSTEM - N-HYDROXYPHTHALIMIDE (NHPI) COMBINED WITH CO(ACAC)(N) (N=2 OR 3)

A novel class of catalysts for alkane oxidation with molecular oxygen was examined. N-Hydroxyphthalimide (NHPI) combined with Co(acac)(n) (n = 2 or 3) was found to be an efficient catalytic system for the aerob ic oxidation of cycloalkanes and alkylbenzenes under mild conditions. Cycloalkanes were successfully oxidized with molecular oxygen in the p resence of a catalytic amount of NHPI and Co(acac)(2) in acetic acid a t 100 degrees C to give the corresponding cycloalkanones and dicarboxy lic acids. Alkylbenzenes mere also oxidized with dioxygen using this c atalytic system. For example, toluene was converted into benzoic acid in excellent yield under these conditions. Ethyl- and butylbenzenes we re selectively oxidized at their alpha-positions to form the correspon ding ketones, acetophenone, and 1-phenyl-1-butanone, respectively, in good yields. A key intermediate in this oxidation is believed to be th e phthalimide N-oxyl radical generated from NHPI and molecular oxygen using a Co(II) species. The isotope effect (k(H)/k(D)) in the oxidatio n of ethylbenzene and ethylbenzene-d(10) with dioxygen using NHPI/Co(a cac)(2) was 3.8.