Boronated enynes as versatile sources of stereodefined and skeletally diverse molecules.

[reaction: see text] The application of a one-pot palladium-catalyzed cycloisomerization of enynes 1/Diels-Alder cycloaddition/allylboration sequence efficiently generates tricyclic structures with complete control of the four stereogenic centers. Ruthenium and platinum catalysts perform distinct transformations providing other isomeric boron-substituted cyclic compounds.

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.