2- Butene stereospecific epoxidation

Stereospecific Epoxidation of 2-Butene. The hydroperoxide epoxidation reaction is stereospecific. Pure cis- and trans-2-butene were epoxi-dized separately by cumene hydroperoxide. The cis olefin gave exclusively cis epoxide, and the trans olefin gave exclusively trans epoxide. In both cases, the epoxide was the sole product formed from the olefin. They can be distinguished easily by their different retention times on a gas chromatography column of 20% diisodecyl phthalate on Chromosorb W(60-80 mesh). They were also identified by comparing their infrared spectra with authentic samples. 

Epoxidation of alkenes is a stereospecific syn addition Which stereoisomer of 2 butene reacts with peroxyacetic acid to give meso 2 3 epoxybu tane Which one gives a racemic mixture of (2/ 3/ ) and (25 35) 2 3 epoxybutane ... 

Figure 11.4 The overall result of epoxidation followed by acid-catalyzed hydrolysis is a stereospecific anti hydroxylation of the double bond. ds-2-Butene yields the enantiomeric 2,3-butanediols tra x-2-butene yields the meso compound.

Epoxidation of cis-2-butene-l,4-diones.3 Enediones that can assume the all s-cis-conformation (A) are oxidized by Mo05 H20 HMPT (2 equiv.) stereospecif-ically to cw-2,3-epoxybutane-l,4-diones (1). 

The synthesis of butadiene dioxide with air at 250° has been described. The epoxidation of 2-butene takes place partly stereospecifically to trans-2,3-epoxybutane. ... 

Epoxidation. Mimoun et at3 report that the M0O5 HMPT complex reacts with olefins to form epoxides in high yield. Alkyl substituents on the double bond increase the rate of epoxidation. Aprotic solvents also enhance the rate highest rates are observed in methylene chloride. The reaction is very slow in DMF or THF. The epoxidation is stereospecific with retention of configuration of the olefin. Thus m-butene-2 is converted into cis-2,3-epoxybutane and >ra . -butene-2 into trans-2,3-epoxybutane. The French chemists proposed the mechanism shown in scheme I. 

A simple synthesis of racemic allomuscarine via stereospecific intramolecular opening of the trans-substituted epoxide ring in butyl 4,5-epoxy-2-hydroxyhexanoate was reported by Chmielewski and Guzik (24,25) (Scheme 2). The furane ester intermediate was obtained in an ene reaction between butyl glyoxylate and 1-butene, followed by epoxidation of the... 

In Section 11.13B we showed the epoxidation of acid-catalyzed hydrolysis of these two epoxides and show what product or products would result from each. Are these reactions stereospecific ... 

For an alkene that shows ds,trans isomerism, epoxidation is also stereospecific the stereochemistry of the product depends on the stereochemistry of the starting alkene. Epoxidation of ds-2-butene, for example, yields only the meso compound cis-2,3-dimethyloxirane, and epoxidation of frans-2-butene yields only the enantiomers of... 

---