2-Amino-4-(2-methoxyphenyl)-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile and 2-amino-4-(2-methoxyphenyl)-7,7-dimethyl-3-nitro-4,6,7,8-tetrahydro-5H-chromen-5-one hemihydrate

Calculations of the conformational preferences of the methoxyphenyl substituent with respect to the pyran ring have been carried out for the two title compounds, C19H20N2O3, (II), and C18H20N2O5 center dot 0.5H(2)O, (III). In both molecules, the heterocyclic ring adopts a flattened boat conformation and the fused cyclohexenone ring adopts a 'sofa' conformation. The dihedral angles between these two at fragments are 14.5 (1) and 9.3 (1)degrees in ( II) and ( III), respectively. In both molecules, the methoxy group of the pseudo-axial aryl substituent is syn with respect to the pyran ring. The dihedral angles between the 2-methoxyphenyl rings and the at parts of the pyran rings are 86.3 ( 1) and 87.0 ( 1)degrees, respectively. In the crystal structure of ( II), intermolecular N - H center dot center dot center dot N and N - H center dot center dot center dot O hydrogen bonds link molecules into a three-dimensional framework. In the crystal structure of ( III), a strong intramolecular N - H center dot center dot center dot O hydrogen bond links the at conjugated H - N - C C - N - O fragment into a six-membered ring. In ( III), the water molecule lies on a twofold axis and forms bifurcated O - H center dot center dot center dot O hydrogen bonds with the NO2 group of the molecule. Also in (III), hydrogen bonds link the organic and water molecules into infinite tapes along the c axis.