Methyl 5′′-chloro-1′,1′′-dimethyl-2,2′′-dioxodispiro[indoline-3,2′-pyrrolidine-3′,3′′-indoline]-4′-carboxylate

In the title compound, C22H20ClN3O4, the central pyrrolidine ring adopts an envelope conformation on the N atom. The indolinone systems are individually roughly planar, with maximum deviations from their mean planes of 0.130 Å for the spiro C atom of the indolinone unit and 0.172 Å for the carbonyl C atom of the 5-chloro-1-methylindolinone unit. They make dihedral angles of 77.7 (8) and 86.1 (8)° with the mean plane through the central pyrrolidine ring. In the crystal, molecules are linked by N—H⋯O hydrogen bonds supported by C—H⋯O contacts into chains along the ab diagonal. The structure also features C—H⋯O hydrogen bonds, forming R 2 2(8) and R 2 2(16) rings and generating a three-dimensional array.

In the title compound, C 22 H 20 ClN 3 O 4 , the central pyrrolidine ring adopts an envelope conformation on the N atom. The indolinone systems are individually roughly planar, with maximum deviations from their mean planes of 0.130 Å for the spiro C atom of the indolinone unit and 0.172 Å for the carbonyl C atom of the 5-chloro-1-methylindolinone unit. They make dihedral angles of 77.7 (8) and 86.1 (8) with the mean plane through the central pyrrolidine ring. In the crystal, molecules are linked by N-HÁ Á ÁO hydrogen bonds supported by C-HÁ Á ÁO contacts into chains along the ab diagonal. The structure also features C-HÁ Á ÁO hydrogen bonds, forming R 2 2 (8) and R 2 2 (16) rings and generating a three-dimensional array.
(Yield = 90%). Single crystals suitable for X-ray diffraction were obtained by slow evaporation of a solution in ethyl acetate at room temperature.

Refinement
The H atom bound to N3 was located in a difference Fourier map and its coordinates and atomic displacement parameter were refined freely. All H atoms bound to C were fixed geometrically and allowed to ride on their parent atoms, with C-H distances fixed in the range 0.93-0.97 Å and with U iso (H) = 1.5U eq (C) for methyl H 1.2U eq (C) for other H atoms. The positions of methyl hydrogens were optimized rotationally.

Figure 1
The structure of showing the atom-numbering scheme. The displacement ellipsoids are drawn at the 30% probability level.

Figure 2
The molecular packing viewed along a. Dashed lines show the intermolecular N-H···O and C-H···O hydrogen bonds.

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.