6124-90-9

The catalytic properties of Ti-YNU-1 for the epoxidation of various alkenes and their derivatives have been investigated in detail, and further were made a comparison with those of Ti-Beta. The much higher efficiency of Ti-YNU-1 than Ti-Beta was observed in catalyzing the epoxidation of alkenes and their electron-rich analogues. Although it was less active in the epoxidation of α,β-unsaturated ketones, it showed much higher stability. In contrast, Ti leaching from the framework sites occurred to Ti-Beta, and the leaching degree increased with the carbon number of ketones. It was also shown that the catalytic conditions, including the Ti content in samples, H 2O2/substrate ratio, reaction temperature and time, acid washing and catalyst amount, significantly influenced the activity, selectivity and H2O2 efficiency. Co-oxidation of different alkenes led to the activity and epoxide selectivity being different from those obtained in the oxidation of single olefin as a result of the differences in adsorption properties of substrates over various titanosilicates, which affected the diffusion of substrate molecules and accounted for the unique shape-selectivity of Ti-YNU-1.

Highly selective photocatalytic epoxidation of olefins proceeds on Ti-containing silica with tetrahedrally coordinated Ti-oride species with molecular oxygen and a simple addition of MeCN. The Royal Society of Chemistry 2005.

Covalent anchoring of 1,4-dimethyl-1,4,7-triazacyclononane on silica gel is the first step in the preparation of a heterogenized Mn catalyst. When H2O2 is used as the oxidant, this material can catalyze the vicinal cis- dihydroxylation of disubstituted olefins, as shown schematically here. Both enantiomers of the product are obtained.

Photocatalytic oxidation of 2-hexene on TiO2 powder was investigated under a stream of oxygen gas. The main product was 2.3-epoxyhexane with the chemical yield ranging from 65% to 83% depending on the TiO2 powders. When trans-2-hexene was used as the starting material, the epoxide was also trans. On the other hand, cis epoxide was the chief product from cis-2-hexene. From mixed 2-hexene (trans/cis = 1.7), larger amounts of trans epoxide were obtained than cis-epoxide in the initial period of the reaction, indicating that trans-2-hexene is more reactive than the cis isomer on the photocatalyst.

A biphasic system using a manganese porphyrin as a catalyst and sodium ascorbate as a reducing agent is able to activate dioxygen and to oxidize olefins selectively into epoxides and alkanes into alcohols and ketones.Its properties and specifities are shown to be different from those of the manganese porphyrin-iodosylbenzene system, suggesting that a manganese -oxo complex is not involved in these O2-dependent oxidations.