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

In the title compound, C27H25ClN2O3, the methylpyrrolidine ring adopts an envelope conformation with the N atom at the flap. The mean plane of the pyrrolidine ring makes dihedral angles of 82.1 (1), 84.4 (1) and 79.8 (1)°, respectively, with the adjacent benzene ring, the mean plane of the indoline ring system and the phenyl ring. The molecular structure is stabilized by intramolecular C—H⋯O hydrogen bonds. In the crystal, molecules are linked into chains along [101] by N—H⋯O hydrogen bonds. C—H⋯π interactions are observed between the chains.

Cg3 is the centroid of the C11-C16 ring.  (Witherup et al., 1995). Oxindole derivatives are of importance in the total synthesis of indole and oxindole alkaloids such as potent inhibitors of monoamine oxidase (MAO) in human urine and rat tissues (Glover et al., 1998). We report herein the crystal structure of the title compound.
In the molecule the pyrrolidine ring (N1/C8-C10) adopts an envelope conformation with N1 atom located at the flap position having asymmetry parameter (Nardelli, 1983)  The structure is stabilized by an intermolecular N-H···O hydrogen bond and C-H···O intramolecular hydrogen bonds.
The crystal structure is further consolidated by C-H ···Cg3 interactions, where Cg3 is the centroid of C11-C16 ring.

Experimental
A mixture of (E)-methyl 2-benzyl-3-(2-chlorophenyl)acrylate (2 mmol, 0.58 g), isatin (2 mmol, 0.29 g) and sarcosine (2 mmol, 0.18 g) in acetonitrile (8 ml) was refluxed for about 10 h. After the completion of the reaction as indicated by TLC, the reaction mixture was concentrated. Then 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 overanhydrous Na 2 SO 4 . The organic layer was concentrated and the crude sample was purified by column chromatography on silica gel (Acme 100-200 mesh), using ethyl acetate:hexane (1:4) to afford the title compound as a colourless solid in 72% yield.

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.