Crystal structure of 7′-(4-chlorophenyl)-2′′-(4-methoxyphenyl)-7′,7a’,7′′,8′′-tetrahydro-1′H,3′H,5′′H-dispiro[indoline-3,5′-pyrrolo[1,2-c]thiazole-6′,6′′-quinoline]-2,5′′-dione and an unknown solvent

The title compound crystallizes with two independent molecules in the asymmetric unit. They differ essentially in the orientation of the 4-methoxyphenyl ring with respect to the pyridine ring of the quinoline moiety.

The asymmetric unit of the title compound, C 34 H 28 ClN 3 O 3 S, contains two independent molecules (A and B). They differ essentially in the orientation of the 4-methoxyphenyl ring with respect to the pyridine ring of the quinoline moiety; this dihedral angle is 37.01 (18) in molecule A but only 7.06 (17) in molecule B. In both molecules, the cyclohexanone ring of the isoquinoline unit has a half-chair conformation. In the pyrrolothiazole ring system, the pyrrolo ring in molecule A has a twisted conformation on the N-C fused bond and an envelope conformation in molecule B with the N atom as the flap. The thiazole rings of both molecules have twisted conformations on the N-C fused bond. In the crystal, the A molecules are linked by pairs of N-HÁ Á ÁO hydrogen bonds, forming inversion dimers with an R 2 2 (8) ring motif. These dimers are linked to the B molecules by an N-HÁ Á ÁN hydrogen bond and a series of C-HÁ Á ÁO hydrogen bonds, forming layers lying parallel to the (101) plane. The layers are linked by C-HÁ Á Á interactions and offsetinteractions [intercentroid distance = 3.427 (1) Å ], forming a supramolecular framework. The contribution to the scattering from a region of highly disordered solvent molecules was removed with the SQUEEZE routine in PLATON [Spek (2015). Acta Cryst. C71, 9-18]. The solvent formula mass and unit-cell characteristics were not taken into account during refinement.

Chemical context
Pyrazolo (Siminoff et al., 1973;Zheng et al., 2006) quinoline ring systems are a privileged class of nitrogen-containing heterocycles endowed with significant biological activities. Quinoline derivatives have been reported to possess many interesting pharmacological activities and they are characteristic components of a large number of biologically active compounds. The wide spectrum of biological effects of these kind of compounds includes anti-viral (Billker et al., 1998;Roma et al., 2000;Chen et al., 2001), and antifungal (Vargas et al., 2003;Singh et al., 1996) agents. In view of their significance, the primary goal of the X-ray diffraction analysis of the title compound was to obtain detailed information on the structural conformation that may be useful in understanding the chemical reactivity of such compounds.

Structural commentary
The molecular structure of the two independent molecules, A and B, of the title compound are given in Figs. 1 and 2, respectively. The molecular overlay of inverted molecule B on molecule A is shown in Fig. 3. The r.m.s. deviation is 0.44 Å with a maximum deviation of 1.931 Å (Mercury; Macrae et al., 2008). The two molecules differ essentially in the orientation of the 4-methoxyphenyl ring (C51A-C56A, C51B-C56B) with respect to the pyridine ring of the isoquinoline moiety (N2A/ C22A-C26A, N2B/C22B-C26B). In molecule A, the dihedral angle between the two rings is 37.01 (18) compared to 7.06 (17) in B. There is also a slight difference in the orientation of the 4-chlorophenyl ring with respect to the mean plane of the pyrrolo ring, viz. in molecule A benzene ring C11A-C16A is inclined to the mean plane of the pyrrol ring (N1A/C1A-C4A) by 86.12 (17) , while in molecule B the corresponding dihedral angle is 76.92 (17) .
The thiazole rings have twisted conformations on bonds C4A-N1A and C4B-N1B for molecules A and B, respectively. The pyrrolo ring (N1A/C1A-C4A) has a twisted conformation on bond C4A-N1A in molecule A, while in molecule B this ring (N1B/C1B-C4B) has an envelope conformation with atom N1B as the flap. The mean planes of the thiazole and pyrrolo rings are inclined to each other by 11.58 (17) in A and 12.79 (18) in B.
As usual for such spiro compounds, the rings involving the spiro atoms (here C2A/C2B and C3A/C3B) are normal to each The molecular structure of independent molecule B of the title compound, showing 30% probability displacement ellipsoids and the atom labelling.

Figure 3
A view of the molecular overlay of inverted molecule B (red) on molecule A (black).

Figure 1
The molecular structure of independent molecule A of the title compound, showing 30% probability displacement ellipsoids and the atom labelling.

Figure 4
A view normal to plane (101) of the crystal packing of the title compound. The hydrogen bonds (see Table 1) are shown as dashed lines. H atoms not involved in these interactions have been omitted for clarity. Table 1 Hydrogen-bond geometry (Å , ).

Synthesis and crystallization
A mixture of isatin (1.1 mmol) and thiazolidine-4-carboxylic acid (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 (E)-6-(4chlorobenzylidene)-2-(4-methoxyphenyl)-7,8-dihydroquinolin-5(6H)-one (1 mmol) was added and the reaction mixture was allowed to reflux 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 90:10 (v/v) petroleum ether-ethyl acetate mixtures to obtain the pure product. The product was dissolved in ethyl acetate and poured into a beaker, covered with perforated film and kept undisturbed. The solvent was allowed to evaporate slowly, yielding colourless block-like crystals after a period of seven days (m.p. 458 K; yield 80%).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The NH H atoms were located in a difference-Fourier map and freely refined. The C-bound H atoms were placed at 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. The residual electron density was difficult to model and therefore, the SQUEEZE routine in PLATON (Spek, 2015) was used to remove the contribution of the electron density in the solvent region from the intensity data and the solvent-free model was employed for the final refinement. The solvent formula mass and unit-cell characteristics were not taken into account during refinement. The cavity of volume ca 418 Å 3 (ca 14% of the unit-cell volume) contains approximately 100 electrons (see Fig. 6).

7′-(4-Chlorophenyl)-2′′-(4-methoxyphenyl)-7′
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.