Methyl 3-[(1H-benzimidazol-1-yl)methyl]-1-methyl-4-(4-methylphenyl)-2′-oxopyrrolidine-2-spiro-3′-1-benzimidazole-3-carboxylate

In the title compound, C29H28N4O3, the pyrrolidine ring adopts a twist conformation whereas the oxindole and benzimidazole residues are approximately planar with maximum deviations of 0.159 (1) and 0.011 (1) Å, respectively. The oxindole residue is almost perpendicular to the benzimidazole residue, making a dihedral angle of 89.2 (1)°. The methyl-substituted benzene ring is oriented at angles of 47.7 (1) and 71.0 (1)°, respectively, with respect to the oxindole and benzimidazole residues. An intramolecular C—H⋯O hydrogen bond is observed. In the crystal, molecules associate via N—H⋯N hydrogen bonds, forming R 2 2(9) dimers.

In the title compound, C 29 H 28 N 4 O 3 , the pyrrolidine ring adopts a twist conformation whereas the oxindole and benzimidazole residues are approximately planar with maximum deviations of 0.159 (1) and 0.011 (1) Å , respectively. The oxindole residue is almost perpendicular to the benzimidazole residue, making a dihedral angle of 89.2 (1) . The methyl-substituted benzene ring is oriented at angles of 47.7 (1) and 71.0 (1) , respectively, with respect to the oxindole and benzimidazole residues. An intramolecular C-HÁ Á ÁO hydrogen bond is observed. In the crystal, molecules associate via N-HÁ Á ÁN hydrogen bonds, forming R 2 2 (9) dimers.
The molecular structure of (I) is illustrated in Fig. 1. The geometry of the pyrrolidine and oxindole residues of (I) compares well with that reported in other related structures (see, for example, Aravindan et al., 2004;Selvanayagam et al., 2005;Seshadri et al., 2003).
The sum of the angles at N1 of the pyrrolidine ring [334.8°] and N3 of the imidazole ring [359.9°] are in accordance with sp 3 and sp 2 hybridizations. Atom O1 is essentially coplanar with the heterocyclic ring to which it is attached, with a deviation of -0.159 (1) Å. Benzimidazole residue is planar with a maximum deviation of -0.011 (1) Å for atom C22. Atom C29 deviates 0.052 (2) Å from the best plane of the methylphenyl ring.
The dihedral angle between the oxindole and benzimidazole residues is 89.2 (1)°. This indicates that the oxindole residue is almost perpendicular to the benzimidazole residue. The methyl phenyl ring is oriented at an angles of 47.7 (1) and 71.0 (1)° with respect to the oxindole and benzimidazole residues.
The molecular structure is influenced by an intramolecular C-H···O hydrogen bonds. Atom O1 acts as a bifurcated acceptor for two intramolecular C-H···O hydrogen bonds. In the molecular packing, N-H···N hydrogen bonds link inversion-related molecules to form R 2 2 (9) graph-set dimer ( Fig.2 and Table 1).

Experimental
To a mixture of isatin (1mmol), sarcosine (1mmol) and Baylis-Hillman adduct (1mmol) was added and heated under reflux in methanol (20ml) until the disappearance of the starting materials as evidenced by TLC. The solvent was removed under vacuo. The crude product was subjected to column chromatography using petroleum ether-ethyl acetate as eluent. Single crystals were grown by slow evaporation from methanol.
supplementary materials sup-2 Refinement H atoms were placed in idealized positions and allowed to ride on their parent atoms, with C-H distances of 0.93-0.97 Å and an N-H distance of 0.86 Å, and Uiso(H) = 1.5U eq (C) for methyl H and Uiso(H) = 1.2U eq (C,N) for all other H atoms.

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.