5-Acetyl-2-amino-6-methyl-4-(1-naphthyl)-4H-pyran-3-carbo­nitrile, methyl 6-amino-5-cyano-2-methyl-4-(1-naphthyl)-4H-pyran-3-carboxyl­ate and tert-butyl 6-amino-5-cyano-2-methyl-4-(1-naphthyl)-4H-pyran-3-carboxyl­ate

Syntheses and X-ray structural investigations have been carried out for the three title compounds, C₁₉H₁₆N₂O₂, (IIIa), C₁₉H₁₆N₂O₃, (IIIb), and C₂₂H₂₂N₂O₃, (IIIc), respectively. In mol­ecules (IIIa) and (IIIc), the heterocyclic ring is practically flat, while in (IIIb) it adopts a flattened-boat conformation. In (IIIb) and (IIIc), the carbonyl group and a double bond of the heterocyclic ring are anti, but in (IIIa) they are syn and the carbonyl group participates in an intra­molecular C—H⋯O hydrogen bond which forms a six-membered ring. In mol­ecules (IIIa) and (IIIc), the dihedral angles between the naphthalene substituent and the flat heterocyclic ring are 96.4 (3) and 102.6 (3)°, respectively. In (IIIb), the dihedral angle between the pseudo-axial naphthalene bicycle and the flat part of the pyran ring is 81.6 (3)°. In the crystal structure of (IIIa), intermolecular N—H⋯N and N—H⋯O hydrogen bonds link the mol­ecules into a three-dimensional framework. In (IIIb) and (IIIc), only one H atom of the NH₂ group takes part in an N—H⋯O hydrogen bond and infinite chains are formed along the a axis.