In the presence of imidazole as an additive, a phosphorus-contg. tetranuclear peroxotungstate, THA3[PO4{WO(O2)2}4] (I, THA = tetra-n-hexylammonium), could act as an efficient catalyst for epoxidn. of cycloaliph. alkenes with 30% aq. hydrogen peroxide (H2O2). Compd. I showed higher catalytic activity and selectivity to epoxide than other tungstates. By using the I/imidazole system, various kinds of cycloaliph. alkenes could be highly selectively converted into the acid-sensitive epoxides including industrially important diepoxide in high to excellent yields under the almost stoichiometric conditions. The 1H NMR spectroscopy showed that imidazole would work not only as a proton acceptor but also as a Lewis base to remarkably suppress the acid-catalyzed ring opening of epoxides. ﾂｩ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. [on SciFinder(R)]
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