Oxacyclopropanes

Cyclic ethers can be named simply as oxacycloalkanes, such as oxacyclopropane, oxacyclo-butane, oxacyclopentane, and oxacyclohexane, where the prefix oxa indicates the replacement of CH2 by O in corresponding cycloalkanes. Most cyclic ethers, however, are known by other names. The 3-, 4-, 5-, and 6-membered rings are oxirane, oxetane, oxolane, and oxane, respectively, or ethylene oxide (or epoxide), trimethylene oxide, tetrahydrofuran, and tetrahydropyran. 

D Oxidation with Peroxidic Compounds. Oxacyclopropane (Oxirane) Formation... 

Alcohols of formula RCH2CH2OH can be prepared by addition of RMgX to oxacyclopropane (oxirane) ... 

Oxacyclopropane (oxirane), the simplest cyclic ether, is an outstanding exception to the generalization that most ethers are resistant to cleavage. Like cyclopropane, the three-membered ring is highly strained and readily opens under mild conditions. Indeed, the importance of oxacyclopropane as an industrial chemical lies in its readiness to form other important compounds. The major products derived from it are shown in Figure 15-5. 

The lesser known four-membered cyclic ether, oxacyclobutane (oxe-tane), (CH2)30, also is cleaved readily, but less so than oxacyclopropane. Oxacyclopentane (oxolane, tetrahydrofuran) is a relatively unreactive water-miscible compound with desirable properties as an organic solvent. It often is used in place of diethyl ether in Grignard reactions and reductions with lithium aluminum hydride. 

Figure 15-5 Important commercial reactions of oxacyclopropane (oxirane, ethylene oxide)...

Oxacyclopropanes also can be prepared from vicinal chloro- or bromo-alcohols and a base. This is an internal SN2 reaction and, if the stereochemistry is correct, proceeds quite rapidly, even if a strained ring is formed ... 

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