Latex supported manganese(III) porphyrin catalysts for oxidations of alkenes by hydrogen peroxide and tert-butyl hydroperoxide in the aqueous medium

Abstract

Cationic polymer latexes were prepared by emulsion copolymerization of vinylbenzyl chloride and divinylbenzene followed by quaternization with trimethylamine and used as catalyst supports for 5,10,15,20-tetrakis(2, 6-dichloro-3-sulfonatophenyl)porphinatomanganese(III) chloride and 5,10,15,20-tetra(4-sulfonatophenyl)porphinatomanganese(III) chloride. The supported catalysts and water soluble analogues were used for oxidation of styrene, 1-decene and cis-cyclooctene by hydrogen peroxide and tert-butyl hydroperoxide in the aqueous phase. The oxidation of 1-decene and cis-cyclooctene failed. In the oxidation of styrene, the porphyrin catalysts in the latex were more active than in solution. The relative molar ratios of oxidant: styrene: Mn porphyrin were 1250: 750: 1, and about 25% styrene conversion in 4 h was obtained. When hydrogen peroxide was employed as oxidant, styrene oxide and benzaldehyde were the major and minor products, respectively, and in the case of tert-butyl hydroperoxide, it was vice versa. The reaction depended on pH, the porphyrin ligand, type of oxidant used and presence of imidazole.