Spiropentane sodium

With sodium methoxide in THF, 1-Me reacts analogously, but the sequence stops at the MIMIRC stage corresponding to 222, i.e. the dimethyl l-chloro-2-(l -methoxycyclopropyl)spiropentane-tran5-l,2-dicarboxylate (219). 

Oxaspiropentanes have been obtained from the cyclopropylide 103, prepared by treatment of cyclopropyldiphenylsulfonium tetrafluoroborate 102 either with sodium methylsulfmyl carbanion in dimethoxyethane at —45 °C or with potassium hydroxide in dimethylsulfoxide at 25 °C. While the reaction of the ylide 103 with a,p-unsaturated carbonyl compounds has resulted in selective cyclopropylidene transfer to the a, 3-carbon-carbon double bond leading to spiropentanes, condensation of 103 with non-conjugated aldehydes and ketones led to oxaspiropentanes such as 104, which have been isolated in 59-100% yields, Eq. (30) 57). 

The difficulty in obtaining this monomer in the pure state arises from the fact that the known methods of preparation involve the simultaneous formation of considerable amounts of the isomers of spiropentane which are difficult to remove. The method adopted as giving the most satisfactory yields is that of Applequist, Fanta, and Henrickson (I, 2). The spiropentane is prepared by reaction of zinc dust with pentaerythrityl tetrabromide in alcohol in presence of the sodium salt of ethylenediamine-tetraacetic acid as complexing agent. The yield of hydrocarbon (spiropentane plus various ethylenic compounds) is of the order of 84%. The spiropentane is obtained in the pure state by treating the mixture with bromine in dibromomethane. The yield of pure spiropentane was found to be 62%. 

The action of metals on 1,3-dihalides is an important method of ring closure for cyclopropanes. Cyclopropane is made by the action of zinc dust at 125° on an acetamide solution of 1,3-dichloropropane. A small amount of sodium iodide is used as a catalyst, and sodium carbonate is added to regenerate iodide ions from the precipitated zinc iodide." Zinc dust in aqueous ethanol is employed in the preparation of 1,1-dialkyl-cyclopropanes from the corresponding 1,3-dibromides and spiropentane from pent aery thrityl tetrabromide." ... 

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