Abstract: The mechanism for the unusual base-induced ring-enlargement reaction of (halomethy1ene) cyclobutanes to 1-halocyclopentenes was examined by C-13 labeling studies with (bromomethy1ene) cyclobutane (l), cis-and trans-1-(bromo-methylene)-3-ethoxy- 2, 2-dimethylcyclobutane (15 and 16), and l-(bromomethylene)-2, 2, 4, 4- tetramethylcyclobutane (22). Two competing processes were found to lead from the vinyl ...
