Abstract: 1, 5-Alkadiynes undergo intramolecular rearrangement at elevated temperatures to give dimethylenecyclobutenes. Thus, at 335 O in a flow system, 1, 5-hexadiyne rearranges rapidly to 3, 4-dimethylenecyclobutene. 1, 5-Heptadiyne rearranges somewhat more slowly, giving l-methyl-3, 4-dimethylenecyclobutene at 377 O, while 1, 2-dimethyl-3, 4- dimethylenecyclobutene is formed from 2, 6-octadiyne at 410". Evidence pertinent to the ...