Electrophilic oxidants were generated in situ from a divanadium-substituted phosphotungstate (Bu4N)4[ホウ-PW10O38V2(ホシ-OH)(ホシ-O)] (I) by protonation of the bridging oxo group with perchloric acid followed by reaction with hydrogen peroxide. I acted as a catalyst for the epoxidn. of alkenes with hydrogen peroxide, for the oxidn. of alkanes with hydrogen peroxide to give alcs., and for the bromination and chlorination of alkenes or electron-rich benzenes with sodium bromide or lithium chloride and hydrogen peroxide to give dibromoalkanes or a dichloroalkane. Epoxidn. and dibrominations performed in the presence of I and hydrogen peroxide were regioselective and diastereoselective; oxidns. in the presence of I were chemoselective and efficiently used the hydrogen peroxide added. [on SciFinder(R)]