1.2- Diols, acetoxy bromides from

OPTICALLY ACTIVE EPOXIDES FROM VICINAL DIOLS VIA VICINAL ACETOXY BROMIDES THE ENANTIOMERIC METHYLOXIRANES... 

If desired, glycidic esters can be derived from a,3-dihydroxy esters, such as (110), by either of two methods. In one method, reaction of the diol with an arenesulfonyl chloride is regioselective, producing the a-arenesulfonate (111) in preference to the 3-sulfbnate. Treatment of (111) with an equivalent of base produces the erythro-glycidic ester (112) in good yield. In the second method, the diol is converted to a bromohydrin (114) via the acetoxy bromide (113). The brotmhydrin (114) affords the threo-g ycidic ester (115) on exposure to potassium caitxHiate in methanol. 

Epoxides from ic-diols. The reaction if secondary, primary v/c-diols with a mixture of 6 M hydrogen bromide in HOAc n suits in a vR -2-acetoxy-l-bromoalkane, which is converted into an alkyloxirane on treaiment with base. The method is suitable for preparation of chiral alkyloxiranes. 

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