OBSERVATIONS RELATING TO THE MODE OF FORMATION OF CYCLOPROPYLIDENE DIMERS IN THE REACTION OF GEM-DIBROMOCYCLOPROPANES WITH METHYLLITHIUM

Treatment of the gem-dibromocyclopropane (5) with methyllithium in die thyl ether at -80 degrees C gives not only the syn- and anti-cycloprop ylidene dimers (12) and (13), respectively, but the related species (1 4) and (15) as well. The isolation of this latter pair of products len ds weight to the argument that beta-halobicyclopropylyllithium compoun ds such as (18) are the immediate precursors to the cyclopropylidene d imers.