1-Phenyl-1-bromocyclopropanes have been prepared via reaction of benzal bromide, potassium t-butoxide, and olefins. Trimethylethylene and cis-butene react so as to yield mainly that cyclopropane in which bromine is cis to the larger number of methyl groups. Rates of addition of the reactive intermediate (relative to iso-butene) have been determined for the several olefins.
