(2-tert-Butyl-3-phenyl-2,3-dihydroisoxazole-4,5-diyl)bis(phenylmethanone)

The phenyl and tert-butyl groups of the title compound, C27H25NO3, exhibit a trans configuration in agreement with the stereochemistry of the Z phenyl-N-tert-butylnitrone starting material. The attached carbonyl groups are not coplanar with the neighboring dihydroisoxazole ring and the phenyl rings they are bonded to, with torsion angles of 59.26 (8), 17.53 (11), 16.52 (12) and 52.86 (7)°. The dihedral angle between the dihydroisoxazole ring and the directly attached phenyl group is 86.86 (8)°. There are two nonclassical intermolecular C—H⋯O hydrogen-bonding interactions that operate together with an intermolecular C—H⋯π interaction to form a supramolecular architecture in the crystal system.

The phenyl and tert-butyl groups of the title compound, C 27 H 25 NO 3 , exhibit a trans configuration in agreement with the stereochemistry of the Z phenyl-N-tert-butylnitrone starting material. The attached carbonyl groups are not coplanar with the neighboring dihydroisoxazole ring and the phenyl rings they are bonded to, with torsion angles of 59.26 (8), 17.53 (11), 16.52 (12) and 52.86 (7) . The dihedral angle between the dihydroisoxazole ring and the directly attached phenyl group is 86.86 (8) . There are two nonclassical intermolecular C-HÁ Á ÁO hydrogen-bonding interactions that operate together with an intermolecular C-HÁ Á Á interaction to form a supramolecular architecture in the crystal system.

Comment
Isoxazolines are an important class of heterocyclic compounds because of their wide variety of applications. In chemistry, they find use as intermediates in organic synthesis (Kiss et al., 2009), and many isoxazoline derivatives are bilologocally active compounds with antimicrobial, anticancer, analgesic and anti-inflammatory properties (Velikorodov and Sukhenko, 2003;Shi et al., 2012;Khan and Lee, 2006). Considering these applications we report the structure of a 4isoxazoline derivative, which was prepared by the 1,3-dipolar cycloaddition reaction of phenyl-N-tert-butylnitrone with dibenzoylacetylene.
The compound ( Fig. 1) crystallizes in the orthorhombic space group Pna2 1 . The torsion angle of 125.52 (18)° of the molecular fragment C24/N1/C17/C18 shows the phenyl and tert butyl groups be trans to each other, which agrees with the stereochemistry of the Z phenyl-N-tert-butylnitrone starting material based on the mechanism of the reaction (Eberson et al., 1998). The dihedral angle of the dihydroisoxazole ring with the directly attached phenyl group is 86.86 (8)°. The carbonyl groups attached are not coplanar with the neighboring dihydroisoxazole ring and the phenyl rings they are bonded to. The carbonyl group between the C1-C6 phenyl ring and the dihydroisoxazole ring significantly deviates from the average planes of the phenyl and the dihydroisoxazole rings, respectively, with the largest deviations being 0.2065 (1) and 0.4366 (1) Å for the O1 atom. The torsion angles between the plane of the carbonyl group (atoms C6, C7, O1 and C8) and those of the phenyl and the dihydroisoxazole rings are 17.53 (11) and 59.26 (8)° respectively. The other carbonyl group between the C11-C16 phenyl ring and the dihydroisoxazole ring also significantly deviates from the planes of the attached phenyl and the dihydroisoxazole rings, respectively, with the largest deviations being 0.4777 (1) and 0.1441 (1) Å for the O3 atom. The torsion angles between the plane of the carbonyl group (atoms C9, C10, O3 and C11) and those of the phenyl and the dihydroisoxazole rings are 52.86 (7) and 16.52 (12)° respectively.
There are two intermolecular C-H···O hydrogen bond interactions ( Fig. 2) between the H atoms attached at the C3 & C25 and O3 & O1 atoms of neighboring molecules with D···A distances of 3.203 (3) and 3.483 (3) Å, respectively. An intermolecular C-H···π interaction (Fig. 3) between the H at C2 and the C18-C23 aromatic ring of an adjacent molecule with an H···π distance of 2.70 Å also supports the interconnection between the molecules. Thus, these intermolecular hydrogen bonding interactions, augmented by a weak C-H···π interaction, play a major role in the formation of the supramolecular network of the molecular units. Fig. 4 shows a packing diagram of the title compound viewed along the c axis direction.

Experimental
The title compound was prepared by adapting a reported procedure (Chakraborty et al., 2012). Phenyl-N-tert-butylnitrone (3 mmol) and dibenzoylacetylene (3 mmol) were added into 15 mL of acetonitrile and stirred for 4 h at room temperature.
The reaction was monitored by TLC using EtOAc/hexane (1:5). The solvent was removed under reduced pressure and the product was purified from the crude by column chromatography on silica gel. Yellow crystals suitable for X-ray structure supplementary materials sup-2 . E69, o1284-o1285 determination were grown from ethanol by slow evaporation (m.p: 110 °C).

Refinement
All H atoms on C were placed in calculated positions, guided by difference maps, with C-H bond distances of 0.93-0.98 Å. H atoms were assigned U iso = 1.2U eq (carrier) or 1.5U eq (methyl C). Omitted owing to bad disagreement were the reflections (1 0 0), (2 0 0) and (1 1 0). In the absence of significant anomalous scattering effects, Friedel pairs have been merged.     Packing diagram of the compound along the c axis.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.11 e Å −3 Δρ min = −0.16 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. 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 > 2sigma(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.