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 at, 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 at heterocyclic ring are 96.4 ( 3) and 102.6 ( 3)degrees, respectively. In ( IIIb), the dihedral angle between the pseudo-axial naphthalene bicycle and the at part of the pyran ring is 81.6 ( 3) degrees. 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.