PPh3-catalyzed [2 + 2 + 2] annulations between two units of an activated terminal alkyne and one unit of an aryl N-tosylimine have been developed to provide a synthetic method for highly substituted dihydropyridines. On the basis of the mechanism of the [2 + 2 + 2] annulation, PPh3-catalyzed [4 + 2] annulations have also been discovered.