Ethyl 4-(4-chloroanilino)-1-(4-chlorophenyl)-2-methyl-5-oxo-2,5-dihydro-1H-pyrrole-2-carboxylate

In the title compound, C20H18Cl2N2O3, the dihedral angles between the central 2,5-dihydro-1H-pyrrole ring and the phenyl rings are 74.87 (9) and 29.09 (9)°. Intramolecular N—H⋯O and C—H⋯O hydrogen bonds occur. In the crystal, pairs of N—H⋯O hydrogen bonds link adjacent molecules into inversion dimers and form an R 1 2(6)R 2 2(10)R 1 2(6) ring motif through C—H⋯O hydrogen bonds.

In the title compound, C 20 H 18 Cl 2 N 2 O 3 , the dihedral angles between the central 2,5-dihydro-1H-pyrrole ring and the two phenyl rings are 74.87 (9) and 29.09 (9) . There is a short N-HÁ Á ÁO contact in the molecule with an S(5) ring motif. In the crystal, pairs of N-HÁ Á ÁO hydrogen bonds link adjacent molecules into inversion dimers which are reinforced by C-HÁ Á ÁO hydrogen bonds, forming an R 1 2 (6)R 2 2 (10)R 1 2 (6) ring motif. The dimers are linked by further C-HÁ Á ÁO hydrogen bonds forming slab-like two-dimensional networks lying parallel to (001).

Comment
Lactam compounds or 2-pyrrolidinones are the aza analogues of lactones. Lactams have received relatively little attention in spite of the fact that they are potentially more effective in a pharmaceutical sense, due to the lower toxicity of the lactam ring with respect to that of the lactone (Dembélé et al., 1992). A number of substances based on the γ-lactam structure have been found in an array of natural products and act as advanced intermediates for the synthesis of many biologically important compounds such as antibiotic and anticancer agents (Nay et al., 2009;Galeazzi et al., 1996;Ghelfi et al., 1999;Hanessian et al., 1996). Also, lactams themselves exhibit interesting biological and pharmacological properties, such as psychotropic, antihypertensive and antimuscarinic activity (Bergmann & Gericke 1990;Moody & Young 1994;Nilsson et al., 1990). Based on such facts, and as an extension of our work on the production γ-lactams, we report in this study the synthesis and crystal structure of another dihydro-pyrrolone derivative.

Experimental
A mixture of 254 mg (2 mmol) of 4-chloroaniline and 232 mg (2 mmol) of ethyl pyruvate was taken in presence of 8 mol % of Fe 3 O 4 nanoparticles in 15 ml ethanol/water (v/v) and was irradiated in a microwave for 30 minutes. The reaction progress was monitored by TLC. After completion of the reaction, the precipitated solid was filtered off, washed with water and recrystallized from ethanol. Single crystals of the title compound were obtained via slow evaporation of an ethanolic solution at room temperature.

Refinement
The C-bound H-atoms were positioned geometrically [C-H = 0.95, 0.98 and 0.99 Å for aromatic, methyl and methylene H, respectively], and refined by using a riding model, with U iso (H) = xU eq (C), where x = 1.5 for methyl H, and x = 1.2 for the other H atoms. The N-bound H-atom was located from a difference Fourier map and refined freely.

Figure 1
The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids for non-H atoms are drawn at the 50% probability level.  Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.