Stereoselective Nickel-Catalyzed [2+2+2] Cycloadditions and Alkenylative Cyclizations of Ene-Allenes and Alkenes

Chemo- and Regioselective Rhodium(I)-Catalyzed [2+2+2] Cycloaddition of Allenynes with Alkynes

A highly chemo- and regioselective partially intramolecular rhodium(I)-catalyzed [2+2+2] cycloaddition of allenynes with alkynes is described. A range of diverse polysubstituted benzene derivatives could be synthesized in good to excellent yields, in which the allenynes served as synthetic equivalent to the diynes. A high regioselectivity could be observed when allenynes were treated with unsymmetrical alkynes.

Stereoselective nickel-catalyzed [2+2] cycloadditions of ene-allenes

A stereoselective nickel-catalyzed [2+2] cycloaddition of ene-allenes is reported. This transformation encompasses a broad range of ene-allene substrates, thus providing efficient access to fused cyclobutanes from easily accessed π-components. A simple and inexpensive first-row catalytic system comprised of [Ni(cod)2 ] and dppf was used in this process, thus constituting an attractive approach to synthetically challenging cyclobutane frameworks under mild reaction conditions.