One-step synthesis of symmetrical 3,3'-substituted 2,2'-bipyridine ligands by cobalt(I)-catalyzed (2+2+2) cycloadditions

Cobalt(I)-catalyzed (2+2+2) cycloadditions between 5-hexynenitrile (1) and 1,3-dynes (2) were used for a one-step synthesis of symmetrical, annelated 3,3'substituted 2,2'-bipyridines. The new method requires the regioselective Co(I)-catalyzed cocylization between 5-hexynenitrile with 1,3-diynes, reversing the usual method in bipyridine synthesis.