An opened route to 1,3-dimethylenecyclobutanes via sequential ruthenium-catalyzed [2+2] cycloaddition of allenyl boronate and palladium Suzuki coupling

The regioselective head-to-head [2 + 2] cyclodimerization of allenyl boronate catalyzed by the ruthenium catalyst [Cp*RuCl(COD)] leads to a novel diboronated 1,3-dimethylenecyclobutane. Consecutive palladium-catalyzed C-C couplings open a route to novel disubstituted 1,3-dimethylenecyclobutane species. The X-ray crystalline structure of the phenyl-substituted 1,3-dimethylenecyclobutane is provided. Copyright © 2005 American Chemical Society.