8-Bromo-3-phenyl-3a,4-dihydro-3H-chromeno[4,3-c]isoxazole-3a-carbonitrile

In the title compound, C17H11BrN2O2, the five-membered isoxazole ring has an envelope conformation with the C atom bearing the phenyl ring as the flap. The pyran ring has a half-chair conformation. In the chromeno ring system, the dihedral angle between the mean plane of the pyran ring and the benzene ring is 4.68 (2)°. The dihedral angle between the mean planes of the chromeno ring system and the isoxazole ring is 13.79 (15)°. The latter forms a dihedral angle of 34.10 (17)° with the phenyl ring. In the crystal, molecules are linked by C—H⋯N hydrogen bonds, forming an undulating two-dimensional network parallel to the ab plane.

In the title compound, C 17 H 11 BrN 2 O 2 , the five-membered isoxazole ring has an envelope conformation with the C atom bearing the phenyl ring as the flap. The pyran ring has a halfchair conformation. In the chromeno ring system, the dihedral angle between the mean plane of the pyran ring and the benzene ring is 4.68 (2) . The dihedral angle between the mean planes of the chromeno ring system and the isoxazole ring is 13.79 (15) . The latter forms a dihedral angle of 34.10 (17) with the phenyl ring. In the crystal, molecules are linked by C-HÁ Á ÁN hydrogen bonds, forming an undulating two-dimensional network parallel to the ab plane.
GS and SA thank UGC, India, for financial support. GS also thanks the SAIF, IIT-Madras, for for the instrumentation facility.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: SU2547).
In the crystal, molecules are linked by intermolecular C-H···N hydrogen bonds forming an undulating twodimensional network parallel to the ab plane ( Fig. 2 and Table 1).

Experimental
To a solution of (E)-2-((4-bromo-2-((E)-(hydroxyimino)methyl)phenoxy)methyl) -3-phenylacrylonitrile (2 mmol) in CCl 4 at 273 -283 K was added pinch wise NCS (4 mmol) over 3 h. After Et 3 N (4 mmol) was added to the reaction mixture which was stirred at room temperature for 2 h. After completion of the reaction, the mixture was evaporated under reduced pressure and the resulting crude mass was diluted with water (15 ml) and extracted with ethyl acetate (3 × 15 ml). The combining organic layer was washed with brine (2 × 10 ml) and dried over anhydrous Na 2 SO 4 . The organic layer was evaporated and purified by column chromatography (silica gel 60-120 mesh; 7% EtOAc in hexanes) to provide the desired pure title product as a colourless solid. Single crystals suitable for X-ray diffraction were obtained by slow evaporation of a solution of the title compound in ethyl acetate at room temperature.

Refinement
All the H atoms were positioned geometrically and constrained to ride on their parent atom: C-H = 0.93, 0.97 and 0.98 A for aromatic, methine and methylene H atoms, respectively, with U iso (H) = 1.2U eq (C).

Figure 1
The molecular structure of the title molecule, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level.

Figure 2
A view along the b axis of the crystal packing of the title compound. The molecules are linked by C-H···N hydrogen bonds (dashed lines; see Table 1 for details). 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.