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

The title compound I, 2,2′-[(2-nitro­phen­yl)methyl­ene]bis­(3-hy­droxy-5,5-di­methyl­cyclo­hex-2-enone), C(23)H(27)NO(6), 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—H⋯O hydrogen bonds, which link mol­ecules into a two-dimensional network parallel to the (001) plane and a chain perpendicular to (1[Image: see text]1). Both title compounds II, ethyl 4-(4-hy­droxy-3,5-di­meth­oxy­phen­yl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexa­hydro­quinoline-3-carb­oxyl­ate, C(23)H(29)NO(6), and III, ethyl 4-(anthracen-9-yl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexa­hydro­quinoline-3-carboxyl­ate, C(29)H(29)NO(3), 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—H⋯O bonding is present in the crystal packing of both compound II and III.