A novel synthesis of methylcyclopropanes

Several methylcyclopropanes have been prepared in 32–96% yield by the reaction of olefins with ethylidene iodide and diethylzinc. The reaction is electrophilic, and proceeds stereospecifically. In the case of the reaction with 1,2-disubstituted olefins, cis and trans olefins affords cyclopropane derivatives whose configurations with respect to the substituents from original olefins are cis and trans, respectively. The reaction yields predominantly the anti isomer from olefins containing the hydroxyl group such as allyl alcohol, 2-buten-1-ol and cyclopenten-4-ol. On the other hand, the syn isomer is obtained predominantly from other types of olefins. Stereochemistry of the reaction is discussed.