Oxiranes syntheses

The most important oxirane syntheses are by addition of an oxygen atom to a carbon-carbon double bond, i.e. by the epoxidation of alkenes, and these are considered in Section 5.05.4.2.2. The closing, by nucleophilic attack of oxygen on carbon, of an OCCX moiety is dealt with in Section 5.05.4.2.1 (this approach often uses alkenes as starting materials). Finally, oxirane synthesis from heterocycles is considered in Section 5.05.4.3 one of these methods, thermal rearrangement of 1,4-peroxides (Section 5.05.4.3.2), has assumed some importance in recent years. The synthesis of oxiranes is reviewed in (B-73MI50500) and (64HC(19-1U). 

A versatile oxirane synthesis via (64) is the sulfur ylide approach (B-75MI50504, cf. 76TL457), which in effect inserts a CR2 group into a carbonyl group (Scheme 71). Older, less generally useful versions of this insertion utilize diazomethane or dibromomethane-butyllithium. 

The remarkable stereospecificity of TBHP-transition metal epoxidations of allylic alcohols has been exploited by Sharpless group for the synthesis of chiral oxiranes from prochiral allylic alcohols (Scheme 76) (81JA464) and for diastereoselective oxirane synthesis from chiral allylic alcohols (Scheme 77) (81JA6237). It has been suggested that this latter reaction may enable the preparation of chiral compounds of complete enantiomeric purity cf. Scheme 78) ... 

A -1,3,4-Oxadiazoline, fluoromethyl-rearrangement, 6, 437 Oxadiazolines alkylation, 6, 431 irradiation, 6, 437 mass spectra, 6, 380 oxirane synthesis from, 7, 117-118 ring cleavage... 

Oxiranes, synthesis, bioactivity, and mechanism of peroxide epoxidation of alkenes 99MI3. 

Equation (5) illustrates an example of the recently developed solid-state oxirane synthesis using iodosobenzene (91CL1391 92CL891). 

H. Paulsen, F. R. Heiker, J. Feldmann, and K. Heyns, Direct synthesis of unsaturated carbohydrates and cyclites from oxiranes, Synthesis, (1980) 636-638. 

Cycloadditions. 3.9 Metal-Catalyzed Reactions. 3.10 Polymerization. 4 Oxiranes Synthesis. 4.1 General Survey of Synthesis. 4.2 Nonenantioselective Methods... 

Oxirane synthesis from [2+1] fragments 1.03.4.2.3(0 Peroxy acid epoxidation... 

If the carbanionic carbon atom in a-halolithium compounds is reacted with carbonyl compounds, a C-C bond is created this provides a convenient, general oxirane synthesis (Eq. 

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