Phosphine-catalyzed [4+2] Annulations of α-Aminonitriles with Allenoates: Synthesis of Functionalized Tetrahydropyridines

Phosphine-catalyzed [4+2] annulations of 2-(acetoxymethyl)buta-2,3-dienoates with alpha-aminonitriles have been developed, in which alpha-aminonitriles serve as C, N-bisnucleophilic reaction partners and 2-(acetoxymethyl) buta-2,3-dienoates as C4 synthons respectively. A number of alpha-aminonitriles could be successfully applied to giving multifunctional desired products using PPh3 as catalyst. This method provides a facile entry to access polysubstituted tetrahydropyridines bearing quaternary carbon centers. The possible reaction mechanism was also proposed.