rac-6-Ethoxy-3,3a,4,9b-tetrahydro-1,3-diphenyl-1H-chromeno[4,3-c]isoxazole-3a-carbonitrile

The title compound, C25H22N2O3, with three stereogenic centres, crystallizes in a centrosymmetric space group as a racemate. The pyran ring adopts a sofa conformation and the five-membered isoxazole ring exhibits an envelope conformation. The dihedral angle between the benzene ring and the mean plane through the near coplanar atoms of the pyran ring is 10.54 (9)°. In the crystal, no significant intermolecular interactions are observed.

The title compound, C 25 H 22 N 2 O 3 , with three stereogenic centres, crystallizes in a centrosymmetric space group as a racemate. The pyran ring adopts a sofa conformation and the five-membered isoxazole ring exhibits an envelope conformation. The dihedral angle between the benzene ring and the mean plane through the near coplanar atoms of the pyran ring is 10.54 (9) . In the crystal, no significant intermolecular interactions are observed.
The dihedral angle between the pyran and the benzene rings (C1-C6) is 7.68 (5)°. Also the dihedral angle between the chromeno ring (fusion of benzene and pyran rings) and isoxazole ring is 40.31 (5)°.
In the chromenoisoxazole moiety, the dihedral angle between the benzene and isoxazole ring is 36.41 (5)° and the dihedral angle between the pyran and isoxazole ring is 42.56 (6)°.
The geometric parameters of the title compound ( Fig. 1) agree well with the reported similar structures (Kanchanadevi et al., 2011;Swaminathan et al., 2012).
The molecular structure is stabilized by C-H··· N intramolecular interaction and the crystal packing is stabilised by C -H··· O and C-H··· N hydrogen bonds (Table 1).

Experimental
A mixture of (E)-2-((2-ethoxy-6-formylphenoxy)methyl)-3-phenylacrylonitrile (2 mmol, 0.61 g) and N-phenylhydroxylamine (3 mmol, 0.33 g) in ethanol (10 mL) was refluxed for 6 h. After the completion of the reaction as indicated by TLC, the reaction mixture was concentrated and the resulting crude mass was diluted with water (15 mL) and extracted with ethyl acetate (3 × 15 mL). The combined organic layer was washed with brine (3 × 15 mL) and dried over anhydrous Na 2 SO 4 , solvent was removed under reduced pressure. The crude mass was purified by column chromatography on silica gel (Acme 100-200 mesh), using ethyl acetate-hexane (1:9) to afford the pure compound as a colourless solid in 76% yield.

Refinement
Hydrogen atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.93 -0.97 Å and U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2 U eq (C) for other H atoms.

Figure 1
The molecular structure of the title compound, showing the atom-numbering scheme and displacement ellipsoids drawn at the 30% probability level. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.