Methyl 4′-(3-bromophenyl)-3′-(2,5-dimethylbenzyl)-1′-methyl-2-oxospiro[indoline-3,2′-pyrrolidine]-3′-carboxylate

In the title compound, C29H29BrN2O3, the indole ring system is essentially planar (r.m.s. deviation = 0.079 Å) and makes a dihedral angle of 85.23 (10)° with the mean plane of the 4-methylpyrrolidine ring. This ring adopts an envelope conformation with the N atom at the flap. The pyrrolidine ring of the indole ring system adopts a twisted conformation on the C—C(=O) bond. The molecular structure is stabilized by an intramolecular C—H⋯O hydrogen bond, which generates an S(6) ring motif. In the crystal, molecules are linked via pairs of C—H⋯O hydrogen bonds, forming inversion dimers with an R 2 2(14) ring motif. These dimers are further linked by N—H⋯O and C—H⋯O hydrogen bonds, forming two-dimensional networks lying parallel to (10-1).

In the title compound, C 29 H 29 BrN 2 O 3 , the indole ring system is essentially planar (r.m.s. deviation = 0.079 Å ) and makes a dihedral angle of 85.23 (10) with the mean plane of the 4methylpyrrolidine ring. This ring adopts an envelope conformation with the N atom at the flap. The pyrrolidine ring of the indole ring system adopts a twisted conformation on the C-C( O) bond. The molecular structure is stabilized by an intramolecular C-HÁ Á ÁO hydrogen bond, which generates an S(6) ring motif. In the crystal, molecules are linked via pairs of C-HÁ Á ÁO hydrogen bonds, forming inversion dimers with an R 2 2 (14) ring motif. These dimers are further linked by N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds, forming two-dimensional networks lying parallel to (101).
The molecular structure of the title compound is illustrated in Fig 1. In the molecule, there is a C-H···O hydrogen bond, forming an S(6) ring motif (Table 1; Bernstein et al., 1995). The indole ring system (N2/C9-C16) is essentially planar with a maximum deviation of -0.136 (2) Å for atom C10. Atom O1 deviates significantly from the mean plane of In benzene ring (C11-C16) of the indole ring system, the expansion of the ipso angles at C11, C13 and C14 [121.8 (2), 121.3 (2) and 120.2 (2)°, respectively] and contraction of the apical angles at C12, C15 and C16 [117.9 (2), 119.1 (2) and 119.56 (19)°, 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 (+)syn-clinal to each other with the torsion angle (C9-C17-C25-O2) of 84.5 (2)°.

Experimental
A mixture of (E)-methyl 3-(3-bromophenyl)-2-(2,5-dimethylbenzyl)acrylate (2 mmol), isatin (2 mmol) and sarcosine (2 mmol) in acetonitrile (8 ml) was refluxed for 12 h. After the completion of the reaction as indicated by TLC, the reaction mixture was concentrated. The resulting crude mass was diluted with water (10 ml) and extracted with ethyl acetate (3 × 10 ml). 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 acetate:hexanes (2:8) to afford the title compound as a colourless solid (Yield 71%). 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: C-H = 0.93 and 0.96 Å for CH and CH 3 H atoms, respectively, with U iso (H) = 1.5 U eq (C-methyl) and = 1.2U eq (C) for other H atoms.

Figure 1
The molecular structure of the title comolecule, with atom labelling. Displacement ellipsoids are drawn at 30% probability level.  Aview of the crystal packing of the title compound, showing the formation of infinite chains C(7) and C(8) and R 2 2 (14) graph-set motifs. The dashed lines indicate hydrogen bonds (see Table 1 for details). 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.