Lacunary Keggin type polyoxotungstates in conjunction with a phase transfer catalyst: An effective catalyst system for epoxidation of alkenes with aqueous H2O2

Na9[SbW9O33] in conjunction with a phase transfer catalyst (methyl tricapryl ammonium chloride) is a highly efficient catalytic system for the selective epoxidation of alkenes with aqueous H2O2 as the oxidant. Importantly, the reactions can be carried out in the absence of any organic solvents. The alkene epoxidation reactions with both, a transition metal ion substituted polyoxotungstate as well as a transition metal ion-free polyoxotungstate precursor indicates that the tungstate group is the active center for the oxidation reaction. It was also observed that the transition metal ion does not play any significant role in the reaction. IR studies support the formation of tungsten-peroxo species and also show that the catalyst is stable in the presence of phase transfer catalyst when aqueous H2O2 is used as an oxidant.

Graphical abstractNa9[SbW9O33] in conjunction with a PTC (methyl tricapryl ammonium chloride) is a highly efficient catalyst for the selective epoxidation of a variety of alkenes using aqueous H2O2 without addition of any solvents. In most cases selectivity for the epoxide was excellent. The reactions can be carried out in the absence of any organic solvents. IR studies support the formation of tungsten-peroxo species and stability of catalyst in the presence of phase transfer catalyst when aqueous H2O2 was used as the oxidant. The catalyst can be reused after careful decomposition of unreacted peroxide of the final reaction mixture.Figure optionsDownload full-size imageDownload as PowerPoint slide