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

Abstract 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-ty...
Ausführliche Beschreibung

Abstract 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} $]3−, under two-phase conditions using ethyl acetate as the solvent. It was found that the lacunary-type catalyst showed higher activity and better recyclability than the complete Keggin-type catalyst under the same reaction conditions. 31P NMR spectroscopy and solubility measurements for the two catalysts revealed that the [$ 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. Ausführliche Beschreibung