Intramolecular cyclization of N-propargylic β-enaminones catalyzed by silver

The efficient synthesis of 1,2-dihydropyridine from the intramolecular cyclization reaction of N-propargylic β-enaminones [R2C(O)CHC(R1)(N(R)CH2CCH), where R = Pr, Bn, Ph, 4-Me-C6H4, R1 = Me, Et, Pr, R2 = CF3, CO2Et] using AgNO3 as a catalyst (12 h at 25 °C) is reported. The products were obtained at good yields (70–90%). In particular, when the reaction of N-propargylic β-enaminone with R = Me was performed over a 24 h period, the intramolecular cyclization resulted in the formation of a pyrrole with 80% yield.