Methyl (E)-2-[(3-chloro-4-cyanophenyl)imino]-4-(4-chlorophenyl)-6-methyl-1,2,3,4-tetrahydropyrimidine-5-carboxylate

In the title compound, C20H16Cl2N4O2, the dihedral angles between the planes of the chlorophenyl, chlorocyanophenylimine and ester groups and the plane of the six-membered tetrahydropyrimidine ring are 86.9 (2), 72.6 (2) and 7.9 (2)°, respectively. The Cl atom substituent on the cyanophenyl ring is disordered over two rotationally related sites [occupancy factors 0.887 (2):0.113 (2)], while the molecular conformation is stabilized by the presence of an intramolecular aromatic C—H⋯π interaction. Both N—H groups participate in separate intermolecular hydrogen-bonding associations with centrosymmetric cyclic motifs [graph sets R 2 2(8) and R 2 2(12)], resulting in ribbons parallel to [010]. Further weak C—H⋯O hydrogen bonds link these ribbons into a two-dimensional molecular assembly.

In the title compound, C 20 H 16 Cl 2 N 4 O 2 , the dihedral angles between the planes of the chlorophenyl, chlorocyanophenylimine and ester groups and the plane of the six-membered tetrahydropyrimidine ring are 86.9 (2), 72.6 (2) and 7.9 (2) , respectively. The Cl atom substituent on the cyanophenyl ring is disordered over two rotationally related sites [occupancy factors 0.887 (2):0.113 (2)], while the molecular conformation is stabilized by the presence of an intramolecular aromatic C-HÁ Á Á interaction. Both N-H groups participate in separate intermolecular hydrogen-bonding associations with centrosymmetric cyclic motifs [graph sets R 2 2 (8) and R 2 2 (12)], resulting in ribbons parallel to [010]. Further weak C-HÁ Á ÁO hydrogen bonds link these ribbons into a twodimensional molecular assembly.

Comment
The multifunctionalized dihydropyrimidones (DHPMs) are prime target molecules for their therapeutic and pharmacological properties (Kappe, 2000). Due to the vast range of applications of this class of compounds we have been investigating conformational and packing features of tetrahydropyrimidine derivatives of this title compound (Nayak et al., 2010;Nayak, Venugopala, Govender et al., 2011;Nayak, Venugopala, Chopra & Guru Row (2011). In a continuation of our work on synthesis of heterocyclic compounds for biological properties, herein we report the single-crystal structure of the title compound, C 20 H 16 Cl 2 N 4 O 2 .

Experimental
A mixture of methyl-2-chloro-4-(p-chlorophenyl)-6-methyl-1,4-dihydropyrimidine-5-carboxylate (1 mmol), 4-amino-2chlorobenzonitrile (1 mmol) and methanamine (1 mmol) in 2-propanol (5 ml) was refluxed for 10 h. The reaction completion was monitored by TLC. The reaction medium was cooled to room temperature, the product was filtered, washed with cold 2-propanol and dried to obtain the crude product. The product was purified by recrystallization using ethanol in 69% yield as a yellow solid (m.p. 431 (2) K). Crystals suitable for single-crystal X-ray study were obtained from methanol solvent using slow evaporation at room temperature.

Refinement
The 3-chloro-4-cyanophenylimino group was treated as disordered over two possible rotation-related sites (A and B), having refined site occupancy factors of 0.887 (2) and 0.113 (2), respectively. All H atoms were positioned geometrically with N-H = 0.88 Å, C-H = 0.95-1.00 Å and refined using a riding model with U iso (H) = 1.2U eq (C/N) except for the methyl group where U iso (H) = 1.5U eq (C).

Computing details
Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae et al., 2008); software used to prepare material for publication: PLATON (Spek, 2009) and PARST (Nardelli, 1995).     where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.41 e Å −3 Δρ min = −0.37 e Å −3 Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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.