Aerobic Oxidation Catalyzed by Mixed Addenda Heteropolyoxometarates

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Oxidations of variountaining vanadium and molybdenum were examined. In addition, the combination of Pd (II) with vanadomolybdophosphate (NPVMo) in the presence of hydroquinone was found to be an efficient catalytic system for the oxidation of alkenes with molecular oxygen. We have obtained the following results in this project.1. Oxidation of various organic substrates with molecular oxygen by NPVMoVanadomolybdophosphate (NPVMo), which can be shown as (NH_4) _5H_6PV_4Mo_8O_<40>, catalyzed the oxidation of aromatic amines, benzyl alcohols and phenols to the corresponding imines, bezaldehydes and quinoes with molecular oxygen under relatively mild conditions.2. Development of indirect oxidation using molecular oxygen as final oxidantHydroquinone was smoothly dehydrogenated with molecular oxygen to quinone by NPVMo. By combination of Pd (II) and this system, anew oxidation system has been developed. Thus, a variety of cycloalkenes such as cyclohexene underwent the acylation in acetic acid by Pd (II) /hydroquinone/NPVMo/O_2 system to form 3-acetoxy-1-cycloalkenes in quantitative yields. When ethyl acrylate and acrylonitrile was allowed to react in ehtanol by the use of this catalytic system, acetalization took place to form the corresponding acetals in good yields.3. Oxidation by the use of N-hydroxyphthalimide as catalystN-Hydroxyphthalimide (NHPI) was found to catalyze the oxidation of benzylic compounds with molecular oxygen to give alcohols or ketones in fair yields. This catalytic oxidation was found to be a novel aerobic oxidation system. The oxidation of alkanes such as cyclohexane was achieved by NHPI in the presence of Co (acac) n (n=2 or 3). For example, cyclohexane was converted to cyclohexanone and adipic acid in fair yields. This method was extended to the aerobic oxidation of various organic substrates.