Hydrogen peroxide epoxidation with

An alternative, milder oxidation method has recently been developed by Richardson and co-workers.41 It was found that hydrogen peroxide together with sodium hydrogen carbonate can efficiently epoxidize... 

Mechanism. The earliest mechanistic interpretation of alka- ini hydrogen peroxide epoxidation waa given by Bunton and Min- who found, for the case of ethylideneaoetone and mesityl oxide, iii>t-nrder kinetics with respect to both the unsaturated ketone and the hydroperoxide anion. Accordingly, the reaction was presumed to occur l.v the path shown in Eq. (Si), step (6) being rate-determining- The... 

Table 4.2 Epoxidation of olefins with aqueous hydrogen peroxide catalysed with TS-1...

The workers proposed that alkyl hydroperoxides and aqueous hydrogen peroxide interact with TS-1 in a similar manner, forming titanium alkyl peroxo complexes and titanium peroxo complexes, respectively. However, the titanium alkyl peroxo complexes were not active because the substrate could not enter the void due to steric effects. Consequently, no activity was possible for either alkane hydroxylation or alkene epoxidation. Comparison with Ti02-Si02/alkyl hydroperoxide for alkane and alkene oxidation indicated that this material was active because the oxidation took place on the surface and not in the pores. Figures 4.4 and 4.5 show the possible mechanisms in operation for the oxidation of alkenes and alkanes with a TS-1/hydrogen peroxide system. 

HFP is thermally stable up to 400°C to SOOT (752°F to 932°F). At about 600°C (1112°F) under vacuum, HFP decomposes and produces octafluoro-2-butene (CF3=CFCp3) and octafluoroisobutylene [44]. Under basic conditions, hydrogen peroxide reacts with HFP to form hexafluoropropylene epoxide, which is an intermediate in the preparation of perfluoroalkylvinyl ethers [45,46]. Hexafluoropropylene readily... 

Reactions of hydroperoxides with oleflns in the presence of a variety of other metal centers have also been investigated. Hydrogen peroxide epoxidizes olefins as well in the presence of oxy compounds of W, Mo, V, Os, Ti, Zr, Th, Nb, Ta, Cr and Ru [411-422]. Although CrOa-oxidation of oleflns has been shown to give epoxides [423-425], chromium complexes such as [Cr(acac)a] are not particularly effective epoxidation catalysts at elevated temperatures [426]. It has recently been shown [427] that OSO4 is an effective catalyst for the hydroxylation of oleflns by tert-butyl hydroperoxide in base equation (268). 

Arsonated polystyrenes (9) in biphasic and triphasic systems may be used to catalyse the epoxidation of olefins by aqueous hydrogen peroxide. Yields with various olefins are uniformly high (58—100%) the mechanism of the epoxidation is similar to that of peroxycarboxylic acids (Scheme 9). 

The reaction of perfluoroalkenes with alkaline hydrogen peroxide is a good general method for the preparation of the corresponding epoxides with the exception of the most reactive of the series, TFEO (eq. 6). 

The alkene is allowed to react at low temperatures with a mixture of aqueous hydrogen peroxide, base, and a co-solvent to give a low conversion of the alkene (29). These conditions permit reaction of the water-insoluble alkene and minimise the subsequent ionic reactions of the epoxide product. Phase-transfer techniques have been employed (30). A variation of this scheme using a peroxycarbimic acid has been reported (31). 

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