HALOMETHYL-METAL COMPOUNDS .30. CH2 TRANSFER TO OLEFINS USING MONOHALOMETHYLMERCURY COMPOUNDS

The reaction of bis(bromomethyl)mercury with olefins at temperatures of 80° or above in inert solvents results in the formation of cyclopropanes via CH2 transfer from the mercurial to the olefin. Bromomethylmercuric bromide is inert under these reaction conditions, but it can be brought into reaction by admixture of 1 molar equiv of diphenylmercury. The latter reacts with BrCH2HgBr to give the reactive bis(bromomethyl)mercury and possibly PhHgCH2Br. Iodomethylmercuric iodide also transfers CH2 to olefins and it also is “activated” by added diphenylmercury. The yields of cyclopropanes and their rates of production are variable, depending on the structure of the olefin. Olefins with electron-attracting substituents and hindered olefins react more slowly than simple alkyl-substituted olefins. The available evidence is against a free carbene mechanism and in favor of a direct reaction between the organomercury reagent and the olefin. Relative re ctivity determinations show that electrophilic attack at the C=C bond is taking place and that steric factors are less important than electronic factors. © 1969, American Chemical Society. All rights reserved.