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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 aerobic oxidation of cycloalkanes and alkylbenzenes under mild conditions. Cycloalkanes were successfully oxidized with molecular oxygen in the presence of a catalytic amount of NHPI and Co(acac)(2) in acetic acid at 100 degrees C to give the corresponding cycloalkanones and dicarboxylic acids. Alkylbenzenes were also oxidized with dioxygen using this catalytic system. For example, toluene was converted into benzoic acid in excellent yield under these conditions. Ethyl- and butylbenzenes were selectively oxidized at their alpha-positions to form the corresponding ketones, acetophenone, and 1-phenyl-1-butanone, respectively, in good yields. A key intermediate in this oxidation is believed to be the phthalimide N-oxyl radical generated from NHPI and molecular oxygen using a Co(II) species. The isotope effect (k(H)/k(D)) in the oxidation of ethylbenzene and ethylbenzene-d(10) with dioxygen using NHPI/Co(acac)(2) was 3.8.

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Vanadomolybdophosphate supported on active carbon, NPV6Mo6/C, catalyzed the oxidation and coupling reaction of 2,3,6-trimethylphenol by dioxygen to give trimethyl-p-benzoquinone and 4,4′-dihydroxy-2,2′,3,3′,5,5′-hexamethylbiphenyl, respectively, depending on the solvent used. Hydroquinones and benzyl alcohol were selectively dehydrogenated by the present system, giving the corresponding p-benzoquinones and benzaldehyde, respectively, in good yields.

Mixed addenda heteropolyoxometalate, NPV6Mo6, was found to be an efficient catalyst for the oxidative dehydrogenation of a variety of benzylic amines to the corresponding Schiff-base imines with molecular oxygen in toluene solution. Under the same reaction conditions, isochroman and indan were respectively oxidized to 3,4-dihydroisocoumarin and 1-indanone with high selectivity.

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A Novel Catalysis of N-Hydroxyphthalimide in the Oxidation of Organic Substrates by Molecular Oxygen.-The yield of the products is affected by the reaction temp., but not by light. The oxidation of cycloalkanes occurs often only under a higher pressure of dioxygen. -(ISHII, Y.; NAKAYAMA, K.; TAKENO, M.; SAKAGUCHI, S.; IWAHAMA, T.; NISHIYAMA, Y.; J. Org. Chem. 60 (1995) 13, 3934-3935; Dep. Appl.