Simple, inexpensive and robust cobalt-based catalytic systems for the [2+2+2] cycloaddition between unactivated nitriles and diarylacetylenes are reported. The present systems tolerate a broad range of aryl and alkyl nitriles and cyanamides as well as various di(hetero)arylacetylenes, allowing for the facile preparation of diverse polyarylated pyridines. Mechanochemistry-enabled multifold cyclodehydrogenation of tetra- and pentaarylpyridine is demonstrated to achieve the synthesis of nitrogen-containing polycyclic aromatic compounds having hitherto unprecedented skeletons.