Epoxidation of olefins and allylic alcohols with hydrogen peroxide catalyzed by heteropoly acids in the presence of cetylpyridinium chloride.

Abstract

The epoxidation of olefins and allylic alcohols with aqueous hydrogen peroxide could be achieved in good yields when catalyzed by heteropoly acids combined with an appropriate ammonium salt under the two-phase condition using chloroform as the solvent. From the results of epoxidation catalyzed by several heteropoly acids, 12-tungstophosphoric acid (WPA) in the presence of cetylpyridinium chloride (CPC) (WPA/CPC system) was found to be the best catalyst (Table 1, Run 3). In the case of terminal olefins such as 1-octene (1), the epoxidation proceeds somewhat slowly to give 1, 2-epoxy octane (2) in 82% yield by prolonged reaction (5hr) (Table 2, Run 1). Dienes, 4-vinyl-1-cyclohexene (3), 5-vinyl-2-norbornene (5), and dicyclopentadiene (7), obtained from Diels-Alder reaction of cyclopentadiene with butadiene, are readily epoxidized in good yields to give their corresponding epoxides, 4, 6 and 8-10, respectively (Table 2, Runs 2-5). The rate of epoxidation depends markedly upon the acidity of the reaction medium, and the epoxidation was found to be facilitated under weak acidic conditions (Figure 1). Allylic alcohols are also epoxidized with ease by the present catalyst-oxidant system to give the corresponding epoxides in good yields (Table 2, Runs 6-8).