Stereo/regio-controlled cyclization of polychlorohex-5-enoic acids into substituted cyclobutanes

A new method of synthesis was developed for functionally substituted cyclobutanecarboxylic acids based on an intramolecular cyclization of derivatives of the 2,2,4,6,6-pentachloro-3,3-dimethylhex-5-enoic acid in the presence of the copper(I) amine complexes. The cyclization proceeds both regiospecifically and stereoselectively, and the stereoisomeric composition of the products depends on the capability of the functional group in the initial polychloroalkenoic acid to coordinate to the transition metal ion. A reaction mechanism is suggested explaining the region/stereo-controlled course of the cyclization process.