SYNTHESIS OF CYCLOPROPANE DERIVATIVES FROM OLEFINS BY THE REACTION WITH ORGANIC GEM-DIHALIDES AND COPPER

A new, versatile, and convenient method for the synthesis of cyclopropane derivatives is reported and involves the reaction of olefins with organic gew-dihalides and copper powder in an aromatic hydrocarbon. The reaction is electrophilic and proceeds stereospecifically, i.e., cis and trans olefins afford cyclopropane derivatives whose configurations with respect to the olefin substituents are cis and trans, respectively. Moreover, ether functions controlled the stereochemistry of the cycloaddition; for example, c-2-methoxybicyclo[4.1, 0]heptane was exclusively obtained from 3-methoxycyclohexene. Isomeric olefins, which would be expected from the insertion of the corresponding free carbenes into C-H bonds, were generally not detected in the reaction mixture. The reaction appears to proceed via organocopper intermediates rather than free carbenes. The reaction with diiodomethane gave cyclopropane derivatives in good yields similar to the corresponding Simmons-Smith reaction. The reaction with trihalomethanes gave the corresponding monohalocyclopropane derivatives, and showed the syn stereoselectivity, The reaction with dibromoacetic esters, contrary to the reaction of diazoacetic esters with olefins, gave the corresponding alkoxycarbonylcyclopropane derivatives and showed syn stereoselectivity when steric repulsion between the alkoxycarbon­ yl group and the olefin substituents was not significant. © 1979, American Chemical Society. All rights reserved.