1-[2-(4-Nitrophenyl)-5-(5-phenyl-1,2-oxazol-3-yl)-1,2,3,4-tetrahydroquinolin-4-yl]pyrrolidin-2-one monohydrate

The title compound, C28H24N4O4·H2O, crystallizes with two organic molecules and two solvent water molecules in the asymmetric unit. The most obvious difference between the molecules is the torsion angles between the isoxazole ring and the benzene and phenyl rings [47.0 (2)/56.4 (2) and 33.3 (2)/11.0 (2)°, respectively]. Another important difference is observed in the rotation of the nitro group with respect to the phenyl groups [3.5 (6) and 31.1 (6)°]. The pyrrolidinone fragment is cis oriented with respect to the 4-nitrophenyl fragment. In the crystal, molecules are linked into centrosymmetric R 4 2(8) and R 4 4(20) motifs by O—H⋯O and N—H⋯O interactions.

The title compound, C 28 H 24 N 4 O 4 ÁH 2 O, crystallizes with two organic molecules and two solvent water molecules in the asymmetric unit. The most obvious difference between the molecules is the torsion angles between the isoxazole ring and the benzene and phenyl rings [47.0 (2)/56.4 (2) and 33.3 (2)/ 11.0 (2) , respectively]. Another important difference is observed in the rotation of the nitro group with respect to the phenyl groups [3.5 (6) and 31.1 (6) ]. The pyrrolidinone fragment is cis oriented with respect to the 4-nitrophenyl fragment. In the crystal, molecules are linked into centrosymmetric R 4 2 (8) and R 4 4 (20) motifs by O-HÁ Á ÁO and N-HÁ Á ÁO interactions.  Table 1 Hydrogen-bond geometry (Å , ). The isoxazoles form a relevant group of biologically active compounds with a wide range of applications, including
A considerable number of methods to synthesize substituted isoxazoles have been published including approaches based on intramolecular cycloadditions, condensations, and intramolecular cyclizations of amino acids. These methods sometimes suffer in their versatility, convenience and yield (Lautens & Roy, 2000). The isoxazole ring can be synthesized by 1,3-dipolar cycloaddition reactions between nitrile oxide and alkyne, and that reaction may be catalyzed by copper(II). Cycloaddition reactions are among the most useful reactions in synthetic and mechanistic organic chemistry (Broggini et al., 2005).
Isoxazoles have a rich chemistry because of their easy reductive cleavage and susceptibility to ring transformations (Kotera et al., 1970). Depending on the substitution patterns, isoxazoles can be used as reagents for the imino-Diels-Alder condensation between anilines, aldehydes and electron-rich alkenes to generate tetrahydroquinolines with different selected substitution patterns. Due to this fact, the combination of the two heterocycles rings into a new chemical entityis of interest as no examples are known on chemical literature to date. Many molecules widely used today consist of fusions of rings; an example is the case of penicillins, where in the isoxazole ring incorporation allowed obtaining stable derivatives catalyzed degradation by gastric acid level (flucloxacillin and cloxacillin).
We report here the crystal structure of a novel synthetic derivative cis quinoline-isoxazole by imino Diels-Alder cycloaddition, Fig. 2 O-H···O and N-H···O interactions, (Bernstein et al., 1995). There are six intramolecular hydrogen bonds which stabilized the molecular conformation in both molecules, Table 1.

Refinement
The positions of the O1W, O2W, N2 and N6 H atoms were refined freely along with isotropic displacement parameters.