Cleavage of oxiranes

Reductive cleavage of oxiranes to alcohols by lithium aluminum hydride is an important reaction (64HC(19-1)199), but the most powerful hydride donor for this purpose is lithium triethylborohydride (73JA8486). 

Regioselective anbd Chemoselective Synthesis of Halohydrins by Cleavage of Oxiranes with Metal Halides," Bonini. C. Righi, G. Synthesis, 1994, 225... 

A further use of reagent 39, namely, in the synthesis of deoxyhalo-geno sugars by way of cleavage of oxiranes, is discussed in Section 11,5 (see p. 278). 

Bromotrimethylsilane has proven to be useful for a wide variety of applications most of them being reviewed.5 8 Other recent applications are mild cleavage of oxiranes,9 the synthesis of glycosyl bromides,10 the selective cleavage of tetrahydro-2,5-dimethoxyfuran and tetrahydro-2,6-dimethoxy-pyran,11 the cleavage of esters and ethers,12 and the synthesis of benzyl bromides.13... 

The complex catalyst Bu3SnI-Bu4PI provides a reagent for the carbonylation of unreactive or acid-sensitive oxiranes to carbonates it has been suggested that the iodide anion plays an effective role in nucleophilic cleavage of oxirane rings907. 

K. Iwata, C. Allyltitanium triphenoxide selective cleavage of oxiranes at the more substituted carbon atom. /. Chem. Soc. Chem. Com-mun. 1990, 906—908. 

Cleavage of oxetanes.1 Oxetanes are cleaved by this salt to the corresponding -y-phenylselenenylpropanol at room temperature, whereas tetrahydrofurans (oxo-lanes) are cleaved only at 60-100°. In each case the less-substituted carbon is attacked by the reagent. Cleavage of oxiranes with this reagent is not regioselective. 

Heterolytic cleavage of oxiranes with Grignard reagents 89UK401. Stereospecific deoxygenation of epoxides to olefins 87H(26)1345. 

Highly acidic or basic aqueous solutions result in hydrolytic cleavage of oxirane rings. The use of biphasic systems in combination with phase-transfer reagents give high selectivity to epoxides. 

Cleavage with pyridine-hydrochloric acid, glacial acetic acid, hydrobromio acid or dioxon-hydrochloride has been employed as methods of cleavage of oxirane rings before their determination [126]. 

N-methylation, which yields the latter derivative (7) (R=Me) under more vigorous methylating conditions, the 5-bromo analogue yielded the 2, 3 5, 6-dianhydride (8). Under acidic conditions, 0-2 participation occurs in the cleavage of oxiran (7), leading either... 

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