Synthesis of 5,6,7,8-tetrahydro-1,6-naphthyridines and related heterocycles by cobalt-catalyzed [2+2+2] cyclizations

Microwave-promoted, cobalt-catalyzed intramolecular [2 + 2 + 2] cyclizations of dialkynylnitriles successfully gave 5,6,7,8-tetrahydro-1,6-naphthyridines. The efficient synthesis of these relatively simple, yet rarely addressed heterocycles enabled the preparation of a collection of these compounds.