Nickel-Catalyzed [2+2+2] Cycloaddition of Diynes and Cyanamides.
A variety of bicyclic N,N-disubstituted 2-aminopyridines have been prepared from diynes and cyanamides by nickel-catalyzed [2+2+2] cycloaddition reactions. The reactions proceeded at room temperature with low catalyst loading to afford 2-aminopyridines in good to excellent yields. The method is amenable to both internal and terminal diynes and proceeds in a regioselective manner. A number of cyanamides with diverse functional group tolerance were used. The intermolecular version employing 3-hexyne and N-cyanopyrrolidine also afforded the desired N,N-disubstituted 2-aminopyridine in good yield.