Ethers five-membered carbocycles

Five-membered carbocycles Ethoxycyclopropane reacted with TCNE in various sob vents. In dioxane and acetonitrile 3-ethoxy-1,1,2,2-cyclopentane-tetracarbonitrile 375 was the only product. Performing the reaction in benzene also yields a ring-opened enol ether, which reacts further with TCNE . 

Shibasaki and co-workers used a ring-closing metathesis approach to prepare a number of five-, six-, and seven-membered rings from electron-deficient olefins. Treatment of acyclic enol ether 18 with 7 mol % of 3 in refluxing benzene provided the corresponding cyclic enol ether 19 in 94% yield. Deprotection of the silyl ether 19 (not shown) resulted in the corresponding cyclic ketone, a valuable synthetic intermediate in natural products synthesis and a number of industrial processes. The authors reported additional examples of the synthesis of five-membered ring carbocycles as part of this study. 

Independently, Aggarawa and co-workers prepared five-, six-, and seven-membered carbocyclic methyl and silyl enol ethers bearing phenyl and... 

In contrast, the related cyclizadons used to form carbocyclic systems have been of limited synthetic value due to the acid sensitive nature of the derived allylic ether product (equation 1 Figure 11). The sensitivity of these carbocycles may be rationalized by considering the poor orbital overlap between the allylic C—O bond with the adjacent ir-bond in a five-, six- or seven-membered ring. ... 

Aggarawa and co-workers applied their strategy for the synthesis of five- and six- membered ring carbocyclic silyl enol ethers to the the synthesis of seven-membered ring carbocyclic silyl enol ether bearing a phenyl substituent. Substrate 230 required upward of 20 mol % of 4 in refluxing benzene to achieve modest yields of the desired product 231. 

In view of the wide distribution of the cyclohexanehexols (called inositols or cyclitols) and the importance of one in particular (myo-inositol) to certain bacteria, plants, and perhaps even to warm-blooded animals, the naturally occurring and synthetic compounds of this carbocyclic class have received considerable study. Naturally occurring members include four inositols, monomethyl ethers, a dimethyl ether, monodeoxy derivatives, one dideoxy derivative, a methyl homolog, and deoxy carboxylic acids. Five inositols and many other synthetic members, including ketones (cycloses or inososes), are known. 

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