Synthesis of Cyclopropyl Ethers and Cyclopropanols by Carbene Transfer – Acetolysis of Cyclopropyl p‐Toluenesulfonates

The reaction of chloromethyl phenyl ether with butyllithium in olefins yields phenoxy‐cyclopropanes. 1‐Chloro‐1‐phenoxycyclopropanes can be prepared in a similar manner, though the yields are poor. Alkoxycyclopropanes are formed when dichloromethyl alkyl ethers are treated with methyllithium/lithium iodide in the presence of olefins. Cyclopropanols can be obtained in good yields by reaction of (β‐chloroethoxy)cyclopropanes either with butyl‐ or ethyllithium or with bases. – As was shown by acetolysis experiments with cyclopropyl p‐toluenesulfonates having a known steric configuration, the rearrangement of a cyclopropyl derivative into an allyl cation proceeds in accordance with the Woodward‐Hoffmann‐DePuy rule. The solvolysis of exo‐bicyclo[n.1.0]alkyl p‐toluene‐sulfonates is assumed to proceed via “semi‐open” intermediates, which are somewhere between an allyl cation and a cyclopropyl cation.