Epoxidation of olefins with hydrogen peroxide catalyzed by a reusable lacunary-type phosphotungstate catalyst

Olefins and allylic alcohols have been epoxidized with commercially available hydrogen peroxide (30% H(2)O(2)) using a phase transfer catalyst, composed of cetyltrimethylammonium cations and a lacunary-type phosphotungstate anion [PW(11)O(39)](7-) or the complete Keggin-type heteropolyanion [PW(12)O(40)](3-), under two-phase conditions using ethyl acetate as the solvent. It was found that the lacunary-type catalyst showed higher activity and better recyclability than the complete Keggin-type catalyst under the same reaction conditions. (31)P NMR spectroscopy and solubility measurements for the two catalysts revealed that the [PW(11)O(39)](7-) anion had a much faster degradation rate than the [PW(12)O(40)](3-) anion in an excess of H(2)O(2), which resulted in the formation of more catalytically active species. As a result, the lacunary-type phosphotungstate anion-based catalyst gave a better catalytic performance than the complete Keggin-type anion in ethyl acetate.