Crystal structure and Hirshfeld surface analysis of 4′-(2-chlorophenyl)-1′-methyl-3′′-phenyl-7′′,8′′-dihydro-5′′H-dispiro[indoline-3,2′-pyrrolidine-3′,6′′-isoquinoline]-2,5′′-dione

In the crystal structure of the title compound, a dispiro[indoline-3,2′-pyrrolidine-3′,6′′-isoquinoline]-2,5′′-dione, C—H⋯O hydrogen bonding predominates, linking molecules to form chains propagating along [100].

Spiro scaffolds are being used more and more in drug discovery because of their built-in three-dimensionality and structural variations, resulting in new synthetic routes to introduce spiro building blocks into more pharmaceutically active molecules (Kobayashi et al., 1991;James et al., 1991). The spiro-pyrrolidine ring system is a structural motif present in many biologically important and pharmacologically relevant alkaloids. Spiro-pyrrolidine-indolin-2-one ring systems are also found in a number of alkaloids of biological importance (Hilton et al., 2000). Some derivatives are used as antimicrobial and antitumour agents (Sundar et al., 2011), or possess analgesic (Crooks & Sommerville, 1982) and antiinfluenza virus (Stylianakis et al., 2003) activities. In view of this importance, the primary goal for the X-ray analyses of the title compound is to obtain detailed information on the structural conformation that may be useful in understanding the chemical reactivity of such compounds.

Supramolecular features
In the crystal, molecules are linked by C-HÁ Á ÁO hydrogen bonds and a weak N-HÁ Á ÁO hydrogen bond, forming chains propagating along the a-axis direction ( Fig. 2 and Table 1). There are no further significant intermolecular interactions present.

Hirshfeld Analysis
The program CrystalExplorer (Wolff et al., 2012) was used to generate the Hirshfeld surfaces mapped over d norm , and the electrostatic potential for the title compound. The contact distances, d i and d e , from the Hirshfeld surface to the nearest atom, inside and outside, respectively, enable the analysis of the intermolecular interactions through the mapping of d norm . Two-dimensional fingerprint plots (Rohl et al., 2008) provide an indication of the intermolecular contacts in the crystal. The hydrogen-bonding network generated in the crystal can be visualized using Hirshfeld surface analysis. The bright-red spots on the Hirshfeld surface mapped over d norm (Fig. 4), with labels H2 and H37A, on the surface represent donors for potential hydrogen bonds (see Table 1); the corresponding acceptor on the surface appears as a bright-red spot at atom O2.

Synthesis and crystallization
An equimolar mixture of 2-phenyl-5,6,7,8-tetrahydro-5quinolinone and 2-chlorobenzaldehyde was dissolved in 10 ml of ethanol followed by the addition of 0.5 equiv. of potassium hydroxide. The mixture was stirred for 1 h at ambient temperature and the precipitate formed was filtered and dried to obtain pure (E)-6-(2-chlorobenzylidene)-2-phenyl-7,8-dihydroquinolin-5(6H)-one (L) in 94% yield (m.p. 323-324 K). A mixture of isatin (1.1 mmol) and sarcosine (1.1 mmol) was taken in 10 ml of acetonitrile in a 50 ml round-bottom flask and heated to reflux for 2 h. Then 1 mmol of L was added to the above reaction mixture and reflux was continued for a further 14 h. After completion of the reaction, as evident from TLC, the solvent was removed under reduced pressure and the residue washed with ice-cold water (50 ml). The crude product was purified by column chromatography using a 90:10 (v/v) petroleum ether-ethyl acetate mixture to obtain the pure product (yield 82%, m.p. 356 K). Colourless block-like crystals were obtained by slow evaporation of a solution in ethyl acetate.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The NH H atom was located in a difference-Fourier map and freely refined. The C-bound H atoms were placed in calculated positions and allowed to ride on their carrier atoms: C-H = 0.93-0.98 Å with U iso = 1.5U eq (C-methyl) and 1.2U eq (C) for other H atoms. Computer programs: APEX2 and SAINT (Bruker, 2004), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).

sup-1
Acta Cryst. Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009). where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.37 e Å −3 Δρ min = −0.46 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.