4′-(2,4-Dichlorophenyl)-1,1′-dimethylpiperidine-3-spiro-3′-pyrrolidine-2′-spiro-3′′-indoline-4,2′′-dione

In the title compound, C23H23Cl2N3O2, the pyrroline ring adopts an envelope conformation and the piperidinone ring assumes a slightly twisted chair form. In the crystal, inversion dimers linked by pairs of N—H⋯O hydrogen bonds generate an R 2 8 graph-set motif and a short Cl⋯Cl contact of 3.478 (1) Å occurs.

In the title compound, C 23 H 23 Cl 2 N 3 O 2 , the pyrroline ring adopts an envelope conformation and the piperidinone ring assumes a slightly twisted chair form. In the crystal, inversion dimers linked by pairs of N-HÁ Á ÁO hydrogen bonds generate an R 2 8 graph-set motif and a short ClÁ Á ÁCl contact of 3.478 (1) Å occurs.

Comment
Pyrrolo ring compounds are prevalent in a variety of biologically active compounds (Watson et al., 2001) and find utility in the treatment of diseases such as diabetes, cancer and viral infections. Since the biological activity depends on the conformation of rings that constitute a molecule, precise description, at atomic resolution, of the title compound is expected to supplement further studies on structure-activity relationships on these compounds. Also, the effect of halogen-subsitutions on the conformation of the molecule and consequently on the packing modes remains an area of immense interest in crystallography (Awwadi et al., 2006).
In the title compound (I), the 5-membered methyl substitued pyrroline ring adopts the envelope conformation with C5 deviating from the plane defined by the rest of the atoms of the ring by 0.639 (2) A° The puckering parameters (Cremer & Pople, 1975) of this ring are Q = 0.431 (2)Å and φ = 331.2 °. The piperidinone ring adopts a slightly twisted chair conformation with the N1A and C4A atoms deviating by about 0.712 (2) and -0.523 (2) A°, respectively, from the plane defined by C2A,C3,C5A and C6A with an r.m.s. deviation of 0.041 A°. The chair conformation is also evident from the corresponding puckering amplitudes [Q=0.561 (2) A°, /q = 16.0 (2)°, /f = 30.8 (6)°]. The oxindole and the dichloro substituted phenyl rings are planar.
These columns resemble a 'ladder-like' arrangement of molecules much similar to the one seen in DNA, except for the twist.
These columns of molecules have interactions that are van der Waals in nature.

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 > σ(F 2 ) is used only for calculating Rfactors(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq