Methyl 3′-benzyl-4′-(2,4-dichlorophenyl)-1′-methyl-2-oxospiro[indoline-3,2′-pyrrolidine]-3′-carboxylate

In the title compound, C27H24Cl2N2O3, the indole ring system is essentially planar, with a maximum deviation of 0.082 (2) Å for the carbonyl C atom. It makes a dihedral angle of 88.53 (6)° with the mean plane of the 4-methylpyrrolidine ring, which adopts an envelope conformation with the N atom at the flap position. The molecular structure is stabilized by intramolecular C—H⋯O hydrogen bonds, which generate S(6) and S(7) ring motifs, and an intramolecular π–π interaction involving the benzyl and dichloro-substituted benzene rings [centroid–centroid distance = 3.6291 (11) Å]. In the crystal, molecules are linked via N—H⋯O hydrogen bonds, forming C(7) chains running parallel to [10-1].

In the title compound, C 27 H 24 Cl 2 N 2 O 3 , the indole ring system is essentially planar, with a maximum deviation of 0.082 (2) Å for the carbonyl C atom. It makes a dihedral angle of 88.53 (6) with the mean plane of the 4-methylpyrrolidine ring, which adopts an envelope conformation with the N atom at the flap position. The molecular structure is stabilized by intramolecular C-HÁ Á ÁO hydrogen bonds, which generate S(6) and S(7) ring motifs, and an intramolecularinteraction involving the benzyl and dichloro-substituted benzene rings [centroid-centroid distance = 3.6291 (11) Å ]. In the crystal, molecules are linked via N-HÁ Á ÁO hydrogen bonds, forming C(7) chains running parallel to [101].

Comment
The derivatives of spiro-oxindole ring systems are used as antimicrobial, antitumor agents and as inhibitors of the human NKI receptor besides being found in a number of alkaloids like horsifiline, spirotryprostatin and (+)elacomine (Hilton et al., 2000).
The molecular structure of the title compound is illustrated in Fig 1. In the molecule, there are C-H···O hydrogen bonds forming S(6) and S(7) ring motifs (Bernstein et al., 1995), and a π···π interaction [Cg(1)···Cg(2) = 3.6291 (11) Å, where Cg1 and Cg2 are the centroids of rings C1-C6 and C19-C24, respectively]. The indole ring system is essentially planar with a maximum deviation of 0.082 (2) Å for atom C10. The mean plane of this indole ring system forms a dihedral angle of 88.53 (6)° with the 4-methylpyrrolidine ring mean plane. The latter forms a dihedral angle of 83.37 (9)° with the benzyl ring which shows that they are almost orthogonal. Atom O1 significantly deviates from the mean plane of In the benzene ring (C11-C16) of the indole ring system, the expansion of the ipso angles at C11, C13 and C14 [121.71 (19), 121.1 (2) and 120.8 (2)°, respectively] and contraction of the apical angles at C12, C15 and C16 [117.9 (2), 119.13 (18) and 119.43 (16)°, respectively] are caused by the fusion of the smaller pyrrole ring to the six-membered benzene ring and the strain is taken up by the angular distortion rather than by bond-length distortions (Allen, 1981). The carboxyl group and oxindole ring system are (-)anti-clinal to each other with torsion angle (C9-C17-C25-O2) of -92.85 (18)°.
The combined organic layers were washed with brine (2 × 10 ml) and dried over anhydrous Na 2 SO 4 . The organic layer was concentrated and the residue purified by column chromatography on silica gel (Acme 100-200 mesh), using ethyl supplementary materials sup-2 . E70, o335 acetate:hexanes (2:8) to afford the title compound as a colourless solid in (65%) yield. Block-like colourless crystals were obtained by slow evaporation of a solution in CHCl 3 .

Refinement
The H atoms could all be located in difference electron-density maps. In the final cycles of refinement they were treated as riding atoms and their distances were geometrically constrained: N-H = 0.86 Å, C-H = 0.93 -0.98 Å with U iso (H) = 1.5 U eq (C-methyl) and = 1.2U eq (N/C) for other H atoms.

Figure 1
The molecular structure of the title molecule, with atom labelling. Displacement ellipsoids are drawn at 30% probability level.   Table 1 for details. Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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.