5-(4-Chlorophenyl)-7-(4-methylphenyl)-4-(pyrrolidin-1-yl)-7H-pyrrolo[2,3-d]pyrimidine

The title compound, C23H21ClN4, contains two molecules (A and B) in the asymmetric unit, which are related to one another by a pseudo-inversion center. The non-aromatic pyrrolidine ring in each independent molecule adopts a half-chair conformation; the ring puckering parameters are θ = 0.407 (3) Å and ϕ = 270.5 (4)°, and the pseudo-rotation parameters are ρ = 72.5 (3)° and τ = 42.2 (2)° for an N—C bond of molecule A, and the corresponding values are 0.415 (3) Å, 271.6 (4)°, 73.6 (3)° and 42.6 (2)° for molecule B. The dihedral angles between the central fused-ring system and the substituted chlorophenyl and methylphenyl rings are 66.35 and 45.59°, respectively, for molecule A, and 64.51 and 41.89° for molecule B. The geometry of all four intramolecular C—H⋯π interactions are of type III. π–π interactions involving the centroids of symmetry-related pyrrole rings of molecule B are 4.390 Å, contributing further to the stability of the molecule.

The title compound, C 23 H 21 ClN 4 , contains two molecules (A and B) in the asymmetric unit, which are related to one another by a pseudo-inversion center. The non-aromatic pyrrolidine ring in each independent molecule adopts a halfchair conformation; the ring puckering parameters are = 0.407 (3) Å and ' = 270.5 (4) , and the pseudo-rotation parameters are = 72.5 (3) and = 42.2 (2) for an N-C bond of molecule A, and the corresponding values are 0.415 (3) Å , 271.6 (4) , 73.6 (3) and 42.6 (2) for molecule B. The dihedral angles between the central fused-ring system and the substituted chlorophenyl and methylphenyl rings are 66.35 and 45.59 , respectively, for molecule A, and 64.51 and 41.89 for molecule B. The geometry of all four intramolecular C-HÁ Á Á interactions are of type III.interactions involving the centroids of symmetry-related pyrrole rings of molecule B are 4.390 Å , contributing further to the stability of the molecule.

Experimental
Crystal data
Two independent molecules A and B of the asymmetric unit [ Fig.1] have similar conformations. The fused pyrrolo pyrimidine rings of A and B in the title compound are practically planar with a dihedral angle of 4.11 (16)° in A and 3.00 (17)° in B. The observed bond lengths and bond angles indicate a significant amount of strain arising due to fusion.
A close observation of the molecular geometry: bond lengths, bond angles including torsional angles of both molecules A and B reveals that two independent molecules of the asymmetric unit are related to each other by a pseudoinversion center. The aromatic pyrrolodine ring of both molecules is puckered to adopt half chair conformation. The ring puckering parameters for mol A corresponding to the atom sequence N24-C25-C26-C27-C28 (Cremer et al., 1975) are Theta In the absence of potential donor-acceptor groups in these heterocyclic compounds, the stability of supra-molecular structure is mainly due to relatively weak but significant C-H···π, π-π interactions. Molecule A and its centro-symmetry related pair gets superimposed centering at 0,0,1. The molecular aggregate so formed are held together by two pairs of C -H···π hydrogen bonds [ Fig.2], one intra involving C25-H251 with Cg(3) (the centroid of the ring C17-C18-C19-C20-C21-C22) and the other intermolecular involving C18-H18 with Cg(1) (the centroid of the ring N6-C5-C4-C9-N8-C7) at 1-x, -y, 1-z. The C-H···π interactions involving molecule B and its symmetry related partner is very similar to that of molecule A but this time centered at 0,1,0. The intramolecular hydrogen bond involves C53-H531 to Cg(4) (the centroid of the ring C45-C46-C47-C48-C49-C50) and the intermolecular hydrogen bond is between C46-H46 with Cg(2) (the centroid of the ring N34-C33-C32-C37-N36-C35) at -x, 1 -y, 2 -z. The details of the geometry of these interation is in Table 1. The striking feature of the C-H···π hydrogen bond is that these interactions do not interlink molecules A and B, but it involves only individual molecules. The interactions involve the same group of moieties of the two molecules and is of same length. All of the four C-H···π interactions are of type-III as described by Malone et al., 1997, indicating an exact similarities in the C-H···π interactions. In addition, direction specific π-π interaction involving symmetry related pyrrole ring of molecule B at -1-x, 1-y, 2-z contribute further to the stability of molecular packing along the [100] direction; their centroids are seperated by 4.390 Å [ Fig.3]. However,this interaction is absent in molecule A. In the molecule, the closest approach distance between two symmetry (x -1,-y + 1, Z+1) related chlorines is 3.883 (2) Å.
The pH of reaction mixture was maintained and the final product was separated from a mixture of ethanol and N,N-dimethylformamide.

Refinement
All the H atoms were placed in geometrically idealized positions with C-H distances of 0.96 Å (methyl) or 0.93 Å (aromatic) and constrained to ride on their parent atoms with U iso (H) = 1.2U eq (C) for the phenyl H atoms and U iso (H) = 1.5U eq (C) for the methyl H atoms.

Figure 1
The molecular structure of (I), showing the atom-labelling scheme and 50% probability displacement ellipsoids.

5-(4-Chlorophenyl)-7-(4-methylphenyl)-4-(pyrrolidin-1-yl)-7H-pyrrolo[2,3-d]pyrimidine
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.18 e Å −3 Δρ min = −0.25 e Å −3 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 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.