Abstract: 1-Alken-5-ynes undergo a reversible Cope-type rearrangement at 340'to give 1, 2, 5-alkatrienes which, in turn, undergo cyclization to 3-and 4-methylenecyclopentenes. The effect of methyl substituents is reported, and possible mechanisms are discussed. ecent studies have revealed interesting thermal R rearrangements of certain alkenynes and alkadiynes. For example, 1-methylene-2-vinylcyclopentane (2) arises from rearrangement ...
