Catalytic epoxidation and sulfoxidation activity of a dioxomolybdenum(VI) complex bearing a chiral tetradentate oxazoline ligand

A dioxomolybdenum(VI) complex bearing a tetradentate anionic N,O oxazoline ligand with four stereocenters has been studied as a catalyst in the liquid-phase epoxidation of 17 different aliphatic and aromatic olefins(including prochiral, racemate or pure enantiomers) using tert-butyl hydroperoxide as the oxidant. Epoxide selectivities of up to 100% and variable epoxide yields (3–100% within 24 h) were obtained. Although the complex generally exhibited low or no chiral induction ability, diastereoselectivity was significant in some cases (in the reaction of limonene, for example). Kinetic studies and recycling tests with the substrates cis-cyclooctene and trans-b-methylstyrene showed that the catalyst is stable and reusable, and recycling is facilitated by immobilization of the complex in a room temperature ionic liquid. Preliminary results show that the complex may have a broad substrate scope, not only for olefin epoxidation, but also for the dehydrogenation of alcohols to carbonyl compounds and the sulfoxidation of sulfides to sulfoxides.

Keywords

Ionic liquids Catalysis Olefins Molybdenum Chiral oxazoline Oxidation Sulfoxidation Peroxides

URI

http://hdl.handle.net/10400.1/5686

Citation

Anabela A Valente. Catalytic Epoxidation and Sulfoxidation Activity of a Dioxomolybdenum(VI) Complex Bearing a Chiral Tetradentate Oxazoline Ligand , Catalysis Letters, 132, 1-2, 94-103, 2009.