PPh_3-catalyzed [2 + 2 + 2] and [4 + 2] annulations: synthesis of highly substituted 1,2-dihydropyridines (DHPs)

摘要

PPh_3-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, PPh_3-catalyzed [4 + 2] annulations have also been discovered.