Catalytic epoxidation of olefins

The tert-huty hydroperoxide is then mixed with a catalyst solution to react with propylene. Some TBHP decomposes to TBA during this process step. The catalyst is typically an organometaHic that is soluble in the reaction mixture. The metal can be tungsten, vanadium, or molybdenum. Molybdenum complexes with naphthenates or carboxylates provide the best combination of selectivity and reactivity. Catalyst concentrations of 200—500 ppm in a solution of 55% TBHP and 45% TBA are typically used when water content is less than 0.5 wt %. The homogeneous metal catalyst must be removed from solution for disposal or recycle (137,157). Although heterogeneous catalysts can be employed, elution of some of the metal, particularly molybdenum, from the support surface occurs (158). References 159 and 160 discuss possible mechanisms for the catalytic epoxidation of olefins by hydroperoxides. 

Catalytic epoxidation of olefins (typical procedure) Solid catalyst (1 g) prepared from XAD-2 resin is stirred with 20 mL of 1.0 M cyclohexane and 1.0 M H2O2 in t-BuOH or dioxane at 60°C for 24 h. Cyclohexenoxide is obtained in a quantitative yield. 

Catalytic Epoxidation of Olefins by Hydroperoxides Catalytic Oxidation of Olefins to Aldehydes... 

Warnmark et al. [12] have reported the formation of a dynamic supramolecular catalytic system involving a hydrogen bonding complex between a Mn(ll I) salen and a Zn(II) porphyrin (Figure 1.4). The salen sub-unit acts as the catalytic center for the catalytic epoxidation of olefins while the Zn-porphyrin component performs as the binding site. The system exhibits low selectivity for pyridine-appended styrene derivatives over phenyl-appended derivatives in a catalytic epoxidation reaction. The... 

Jonsson, S., Odille, F.G.J., Norrby, P.-O. and Wammark. K. (2005) A dynamic supramolecular system exhibiting substrate selectivity in the catalytic epoxidation of olefins. Chem. Commun., 549-551,... 

Jonsson, S., Odille Fabrice, G.J., Norrby, P.-O. and Warnmark, K. (2006) Modulation of the reactivity, stability and substrate- and enantioselectivity of an epoxidation catalyst by noncovalent dynamic attachment of a receptor functionality - aspects on the mechanism of the Jacobsen-Katsuki epoxidation applied to a supramolecular system. Org. Biomol. Chem., 4, 1927-1948 Jonsson, S., Odille Fabrice, G.J., Norrby, P.-O. and Warnmark, K. (2005) A dynamic supramolecular system exhibiting substrate selectivity in the catalytic epoxidation of olefins. Chem. Commun., 549-551. 

In situ Catalytic Epoxidation of Olefins with Tetrahydrothiopyran-4-one and Oxone 2-Methyl-2,3-diphenyloxirane. 

Catalytic epoxidation of olefins by various forms of bound oxygen (ROOH, H202, peroxy acids) in the liquid phase was comprehensively studied in a review [132, 133] in which... 

IN SITU CATALYTIC EPOXIDATION OF OLEFINS WITH TETRAHYDR0THI0PYRAN-4-0NE AND OXONE trans-2-METHYL-2,3-DIPHENYLOXIRANE (Oxlrane, 2-methyl-2.3-dlphenyl-, trans-)... 

V. B. Valodkar, G. L. Tembe, M. Ravindranathan, H. S. Rama, Catalytic epoxidation of olefins by polymer-anchored amino acid ruthenium complexes. React. Funct. Polym. 56 (2003) 1. 

The most well-known example is the catalytic epoxidation of olefins with alkyl hydroperoxides that is used for the commercial production of propylene oxide (see earlier). The reaction is catalyzed by high-valent compounds of early transition metals, e.g. Movl, WVI, Vv and TiIV, and involves a peroxometal type mechanism [6,7] as shown (reaction 12). Mo compounds are particularly effective homo-... 

Peroxo and alkylperoxo metal conqilexes are presumed intermediates in the homogeneous and heterogeneous catalytic epoxidations of olefins. Both solid and soluble versions containing high valent, d transition metal ions activate peroxides heterolytically, thereby facihtating oxygen atom transfer to electron-rich substrates... 

First success of catalytic epoxidation of olefins by an electron-rich iron(lll) porphyrin complex and HjO Imidazole effect on the activation of HjOj by iron pwrphyrin complexes in aptotic solvent. J. Inorg. Biochem. 80, 219-225. 

Hofen, W. Thiele, G.A. Continuous and Cost-Effective Process for the Catalytic Epoxidation of Olefins for the Manufacture of Propylene Oxide from... 

According to Ullrich [25] and Groves et aJ. [36-39], iodosylbenzene can serve as the source of 0-atoms in the catalytic epoxidation of olefins (and oxygenation of alkanes) in the presence of metalloporphyrin complexes. The reason for the considerable success of this oxygen source is that PhIO and the iodobenzene (Phi) formed upon 0-atom transfer are both quite stable to oxidation. So the otherwise unstable oxometal species generated from a metalloporphyrin and PhIO for example remains unchanged for extended periods of time, permitting spectroscopic characterization and/or selective reactions with oxidizable substrates. The 0-atom of PhIO is, however, activated for... 

Figure 21.8. Catalytic epoxidation of olefins by (TBA)4 [(PhPO)2SiW 10O36] with H2O2 inCH3CN. Table 21.7. MW-assisted oxidation with H2O2 catalyzed by (TBA)4[(PhPO)2SiWio036]. ...

A detailed account of the mechanisms of catalytic oxidation processes has been published. The mechanisms of the catalytic oxidation of terminal oleffns to methyl ketones and of the catalytic epoxidation of olefins with hydroperoxides have also been reviewed. The latter reactions are generally thought to proceed via direct attack of the substrate upon an electrophilic oxygen of a metal peroxo species rather than prior complexa-... 

Catalytic epoxidation of olefins in systems containing metal catalyst and stoichiometric oxidant is often carried out in the presence of water. Water is often present in such systems just because some of the most popular stoichio-... 

Review "Metal Ketenides in the Catalytic Epoxidation of Olefins"... 

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