Synthesis and crystal structures of a bis­­(3-hy­dr­oxy-cyclo­hex-2-en-1-one) and two hexa­hydro­quinoline derivatives

The title compound I, 2,20 -[(2-nitrophenyl)methylene]bis(3-hydroxy-5,5-dimethylcyclohex-2-enone), C23H27NO6, features a 1,3-ketone–enol conformation which is stabilized by two intramolecular hydrogen bonds. The most prominent intermolecular interactions in compound I are C—HO hydrogen bonds, which link molecules into a two-dimensional network parallel to the (001) plane and a chain perpendicular to (111). Both title compounds II, ethyl 4-(4-hydroxy3,5-dimethoxyphenyl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3- carboxylate, C23H29NO6, and III, ethyl 4-(anthracen-9-yl)-2,7,7-trimethyl-5-oxo1,4,5,6,7,8-hexahydroquinoline-3-carboxylate, C29H29NO3, share the same structural features, such as a shallow boat conformation of the dihydropyridine group and an orthogonal aryl group attached to the dihydropyridine. Intermolecular N—HO bonding is present in the crystal packing of both compound II and III.