Efficient Epoxidation of Olefins with ≥99% Selectivity and Use of Hydrogen Peroxide

Abstract

Epoxides are an important class of industrial chemicals that have been used as chemical intermediates. Catalytic epoxidation of olefins affords an interesting production technology. We found a widely usable green route to the production of epoxides: A silicotungstate compound, [gamma-SiW10O34(H2O)2]4-, is synthesized by protonation of a divacant, lacunary, Keggin-type polyoxometalate of [gamma-SiW10O36]8- and exhibits high catalytic performance for the epoxidation of various olefins, including propylene, with a hydrogen peroxide (H2O2) oxidant at 305 kelvin. The effectiveness of this catalyst is evidenced by >/=99% selectivity to epoxide, >/=99% efficiency of H2O2 utilization, high stereospecificity, and easy recovery of the catalyst from the homogeneous reaction mixture.

Covalent Heterogenization of a Discrete Mn(II) Bis-Phen Complex by a Metal-Template/Metal-Exchange Method: An Epoxidation Catalyst with Enhanced Reactivity

“…Ethyl 4-(3-(triethoxysilyl)propylthio)-1,10-phenanthroline-3-carboxylate, 1 H (Scheme 1), was prepared by adding 6 g of 4-hydroxy- [1,10]phenanthroline-3-carboxylic acid ethyl ester 37 to 20 mL of SOCl 2 and a catalytic amount of DMF for 1 h at 85 °C. After cooling, the SOCl 2 was removed under vacuum and the product separated as a solid from a mixture of 500 mL of 10% K 2 CO 3 and 500 mL of ethyl acetate to give 5.3 g of crude 4-chloro- [1,10]phenanthroline-3-carboxylic acid ethyl ester.…”

“…After cooling, the SOCl 2 was removed under vacuum and the product separated as a solid from a mixture of 500 mL of 10% K 2 CO 3 and 500 mL of ethyl acetate to give 5.3 g of crude 4-chloro- [1,10]phenanthroline-3-carboxylic acid ethyl ester. This material was recrystallized from hot heptanes (75% yield).…”

“…7 For these reasons, much attention has focused on the development of heterogeneous catalysts for epoxidation reactions. [7][8][9][10][11][12] The first covalently attached epoxidation catalysts involved titanium embedded in silica supports 13 and many variations on this theme of Lewis acid transition metals (Ti IV , W VI , Mo VI , V V , Cr VI , Zr IV ) incorporated into silica supports have followed over the past 40 years. E-mail: stack@stanford.edu.…”

“…[8][9][10][11][25][26][27] Few of these materials, however, maintain high reactivity with terminal olefins and are even less effective with more electron-deficient olefins such as α,β-unsaturated ketones and esters. The few heterogenized transition metal catalysts that epoxidize electron-deficient olefins, such as a covalently tethered Ru-porphyrin system, 24 have limitations including multiple reaction byproducts and a narrow substrate scope.…”

Oxo‐Metalate Building Blocks: Conceptual Competitors for Tetravalent Carbon?

“…This inaugurated new directions in synthesis, leading to an explosion in reports of a variety of compounds for use in an expanding range of applications. This tendency was supported by the fact that POM reduction potentials, acidities, and other properties are relevant, for example, for green chemistry, [8] renewable energy (Figure 3), [9][10][11] or catalysis [12,13] (model compounds are also considered [14] ). Parallel to the above developments, the discovery of giant molybdenum/tungsten oxide clusters (obtained under reducing conditions according to a type of growth process) containing up to 368 metal atoms [15] was considered by the scientific community as a breakthrough because it was the route to new length scales and provided the option to discover a variety of new phenomena, including those related to processes under confined conditions.…”