Ring-Opening Reactions of Cyclopropenedicarboxylates with Organolithiums and Organozincs

Ring-opening reactions of cyclopropenedicarboxylates with organolithiums and organozincs have been studied. Organolithiums and dialkyl-or diphenylzincs afforded a series of 1-alkenyl malonates with attack occurring by the organic group from the organometallic reagent at the less substituted sp(2)-hybridized carbon of the cyclopropene moiety. Mechanistic studies proved both anion and dianion intermediates are involved in the reactions with organolithiums. Phenylcyclopropenedicarboxylate and phenylzinc bromide underwent a ring-opening dimerization to afford a 1,4-enyne product.