Epoxidation Hydrogen peroxide-Sodium tungstate

Payne and Williams found that maleic, fumaric, and crotonic acid are very resistant to attack by peracetic or perbenzoic acid but are converted into their epoxides in yields of 77, 50, and 50% by hydrogen peroxide-sodium tungstate at pH 4-5.5. Addition of the peroxide initiates an exothermal reaction which is... 

The observed stereochemistry of addition suggests that oxiranes (epoxides) may be intermediates. Oxiranes may, indeed, be isolated from the reaction of certain alkenes with hydrogen peroxide in the presence of sodium tungstate. °... 

Initially, /-menthyl 2-cyano-3-methyI-2-pentenoate, and /-menthyl and r/-bornyl cy-clopentylidenecyanoacetateswere epoxidized with hydrogen peroxide in the presence of sodium tungstate. Some asymmetric induction was achieved, but the degree of diastereoselectivity was not estimated26. In the final step of the synthesis of the antibiotic phosphonomycin, (Z)-propenylphosphonic acid was epoxidized under Weitz-Scheffer conditions and 92% optically pure phosphonomycin (+ )-x-phenethylammonium-c -epoxypropylphosphonate crystallized from the reaction mixture. It is unclear whether an asymmetric induction occurs during the epoxidation step and to what extent27. 

Hydrogen peroxide or t-butyl hydroperoxide may be used in the presence of a catalyst such as sodium tungstate(VI) or vanadyl acetylaceto-nate [ MeC0CH=C(0 )Me 2V0] for the epoxidation of allylic alcohols. The stereochemistry of the hydroxyl group has a profound effect on the stereochemistry of epoxidation. A system which has been applied to allylic alcohols, to make optically active epoxides, utilizes titanium(rV) isopropoxide, t-butyl hydroperoxide and either of the enantiomeric forms of diethyl tartrate. This system forms chiral epoxides of predictable stereochemistry. When the reactivity of epoxides is combined with the... 

The hydrolysis of cw-epoxysuccinic acid (the initial product in the hydroxyla-tion reaction of maleic acid by hydrogen peroxide) by H2O2 is accelerated by the epoxidation catalyst sodium tungstate. The reaction is first-order within respect to the concentrations of the catalyst and the epoxide and end-product inhibition was observed. ... 

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