(2S,5S,6R)-5-(4-Methylphenyl)-3-phenyl-4,8-dioxa-3-azatricyclo[7.4.0.02,6]trideca-1(13),9,11-triene-6-carbonitrile

In the title compound, C24H20N2O2, the six-membered pyran ring adopts a half-chair conformation with one C atom deviating from the mean plane of the remaining ring atoms by 0.654 (6) Å. The five-membered isoxazole ring adopts an N-envelope conformation with the N atom displaced by 0.742 (5) Å from the mean plane formed by the remaining ring atoms. The carbonitrile side chain is almost linear, with a C—C—N angle of 178.6 (5)°. The crystal packing is stabilized by intermolecular C—H⋯N interactions, through bifurcated acceptor hydrogen bonds formed between the carbonitrile N atom and two alternate C atoms in the unsubstituted benzene ring. The molecular structure and crystal packing are further stabilized by intramolecular and intermolecular C—H⋯π interactions.

In the title compound, C 24 H 20 N 2 O 2 , the six-membered pyran ring adopts a half-chair conformation with one C atom deviating from the mean plane of the remaining ring atoms by 0.654 (6) Å . The five-membered isoxazole ring adopts an Nenvelope conformation with the N atom displaced by 0.742 (5) Å from the mean plane formed by the remaining ring atoms. The carbonitrile side chain is almost linear, with a C-C-N angle of 178.6 (5) . The crystal packing is stabilized by intermolecular C-HÁ Á ÁN interactions, through bifurcated acceptor hydrogen bonds formed between the carbonitrile N atom and two alternate C atoms in the unsubstituted benzene ring. The molecular structure and crystal packing are further stabilized by intramolecular and intermolecular C-HÁ Á Á interactions.

Comment
There has been a flurry of activity on the synthesis of benzopyran and isoxazolidine derivatives owing to their well established biological and pharmacological activities. For example, some benzopyran derivatives exhibit anti-HIV activities (Kashiwada et al., 2001). Similarly, isoxazolidine derivatives exhibit anti-fungal (Mullen et al., 1988), anti-inflammatory (Green et al., 1982) and other such biological activities. In this paper we report the synthesis and crystal structure of the title compound which comprises an isoxazole ring, trans-fused with the pyran ring of the chromene moiety, a methyl benzene ring and a carbonitrile group cis-attached to the adjacent carbon atoms and a benzene ring attached to the nitrogen atom of the isoxazole ring.
In the title molecule ( Fig. 1), the six membered pyran ring adopts a half-chair conformation with puckering parameters (Cremer & Pople, 1975): Q = 0.487 (4) Å, θ = 54.1 (5)° and φ = 288.0 (5)°; the carbon atom C9 deviates from the mean plane by 0.654 (6) Å. The five membered isoxazole ring adopts an N-envelope conformation with N1 displaced by 0.742 (5) Å from the mean plane formed by the rest of the ring atoms. The carbonitrile side-chain is almost linear, with C-C-N angle of 178.6 (5)°, which is in agreement with the observations made in another similar reported structure (Swaminathan et al.,

2011).
The molecular structure is stabilized by a C-H···Cg1 intramolecular interaction (Fig 1); Cg1 is the center of gravity of the phenyl ring (C19-C24). The crystal packing is stabilized by two C-H···N intermolecular interactions, through bifurcated hydrogen bonds formed between the carbonitrile N atom and two alternate C atoms in the unsubstituted benzene ring and a C-H···Cg2 intermolecular interaction (Table 1); Cg2 is the center of gravity of the phenyl ring (C12-C17). The packing arrangement of the title compound is shown in Fig. 2.

Experimental
The title compound was synthesized using Baylis-Hillman derivatives through in situ formation of nitrones followed by an intramolecular [3 + 2] dipolar cycloaddition reaction sequence (Bakthadoss & Murugan, 2010). A mixture of (E)-2-((2-Formylphenoxy)methyl)-3-o-tolylacrylonitrile (2 mmol, 0.75 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 x 15 ml). The combined organic layer was washed with brine (3 x 15 ml) and dried over anhydrous Na 2 SO 4 . The solvent was removed under reduced pressure. The crude mass was purified by column chromotography on silica gel (Acme 100-200 mesh), using ethyl acetate-hexane (1:9) to provide the pure title compound as a colourless solid in 80% yield. Block-shaped single crystals of the title compound suitable for X-ray diffraction analysis were obtained from a solution of ethyl acetate by slow evaporation at room temperature.

Refinement
The hydrogen atoms were placed in calculated positions with C-H = 0.93, 0.96, 0.97 and 0.98 Å for aryl, methyl, methylene and methyne type H-atoms, respectively, and refined in the riding mode with fixed isotropic displacement parameters: U iso (H) = 1.5 U eq (C) for methyl and U iso (H) = 1.2 U eq (C) for other H-atoms. In the absence of significant anomalous dispersion effects, an absolute structure was not determined, and 1859 Friedel pairs were merged.