rac-Methyl (1R,3′S)-1′,1′′-dimethyl-2,2′′-dioxo-2H-dispiro[acenaphthylene-1,2′-pyrrolidine-3′,3′′-indoline]-4′-carboxylate

In the title compound, C26H22N2O4, the pyrrolidine ring adopts a twisted conformation and the other five-membered rings adopt envelope conformations with the spiro C atoms as the flap atoms. The naphthalene ring system of the dihydroacenaphthylene group forms dihedral angles of 89.2 (9) and 75.5 (6)° with the pyrrolidine and indole rings, respectively. The pyrrolidine ring makes a dihedral angle of 80.1 (9)° with the indole ring. In the crystal, molecules are linked by weak C—H⋯O hydrogen bonds, forming chains along the b-axis direction.

In the title compound, C 26 H 22 N 2 O 4 , the pyrrolidine ring adopts a twisted conformation and the other five-membered rings adopt envelope conformations with the spiro C atoms as the flap atoms. The naphthalene ring system of the dihydroacenaphthylene group forms dihedral angles of 89.2 (9) and 75.5 (6) with the pyrrolidine and indole rings, respectively. The pyrrolidine ring makes a dihedral angle of 80.1 (9) with the indole ring. In the crystal, molecules are linked by weak C-HÁ Á ÁO hydrogen bonds, forming chains along the b-axis direction.
Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 2012); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009). et al., 1998;Wright et al., 2000). It may be produced by metabolic processes in termites or by associated microorganisms which inhabit, e.g., the termite guts (Varma et al., 1994). In view of these importance and continuation of our work on the crystal structure analyis of napthalene derivatives, the crystal structure of the title compound has been carried out and the results are presented here.

Experimental
To a mixture of 1eq of (E)-methyl 2-(1-methyl-2-oxoindolin -3-ylidene) acetate, 1eq of isatin and 1.5eq of acenaphthylene-1,2 -dione were dissolved in acetonitrile. This reaction mixture refluxed at 80°C for 8 hours. The reaction mixture was monitored for completion by thin layar chromatography. Upon completion, the reaction mixture was extracted with ethyl acetate and water. The product was dried and purified by coloumn chromatography using ethyl acetate and hexane (1:9) as an elutent to affored pure Dispiro oxindole. Yield (78%). 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 H atoms were fixed geometrically and allowed to ride on their parent C atoms, with C-H distances fixed in the range 0.93-0.97 Å with U iso (H) = 1.5U eq (C) for methyl H 1.2U eq (C) for other H atoms. The positions of methyl hydrogens were optimized rotationally.

Figure 1
The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms are presented as small spheres of arbitrary radius.  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.