3-(2,4-Dichlorophenoxy)-1-(4-methoxybenzyl)-4-(4-nitrophenyl)azetidin-2-one

The β-lactam ring of the title compound, C23H18Cl2N2O5, is nearly planar [maximum deviation = 0.019 (2) Å for the N atom] and its mean plane makes dihedral angles of 56.86 (15), 68.83 (15) and 83.75 (15)° with the dichloro-, nitro- and methoxy-substituted benzene rings, respectively. In the crystal, molecules are linked by pairs of C—H⋯O hydrogen bonds, forming inversion dimers with R 2 2(10) loops. The dimers are linked by further C—H⋯O hydrogen bonds, forming sheets lying parallel to (001). The molecular packing is further stabilized by C—H⋯π interactions.


Comment
The β-lactam (2-azetidinone) ring is the most well known heterocycle to have been studied during the last century (Pitts & Lectka, 2014;France et al., 2004;Arya et al., 2014). The β-lactam framework is the structural element of a large class of broad-spectrum antibiotics such as penicillins, cephalosporins and monobactams (Delpiccolo et al., 2003;Schunk & Enders, 2000;Banik et al., 2003), that effectively combat bacterial infections (Schunk & Enders, 2000). However, the need for new antibiotics has been growing, as a result of the rapid emergence of bacterial strains′ resistance to traditional drugs (Hodous & Fu, 2002;Delpiccolo et al., 2003). Therefore, in continuation of our research on the synthesis of βlactams, we describe herein the synthesis and crystal structure of the title compound.
The bond lengths and bond angles are within normal values and are comparable with those reported for similar compounds (Akkurt et al., 2011;Butcher et al., 2011).
In the crystal, molecules are linked by a pair of C-H···O hydrogen bonds forming inversion dimers with R 2 2 (10) loops (Table 1 and Fig. 2). The dimers are linked by further C-H···O hydrogen bonds forming sheets lying parallel to (001). The molecular packing is further stabilized by C-H···π interactions (Table 1).

Experimental
A mixture of N-(4-nitrobenzylidene) (4-methoxyphenyl) methanamine (0.27 g, 1.00 mmol), 2,4-dichlorophenoxyacetic acid (0.34 g, 1.50 mmol), tosyl chloride (0.28 g, 1.50 mmol) and triethylamine (0.25 g, 2.50 mmol) in dry CH 2 Cl 2 was stirred at room temperature overnight. After completion of the reaction, monitored by TLC, the mixture was washed with HCl (1 N), saturated sodium bicarbonate solution, brine, dried over anhydrous Na 2 SO 4 and the solvent was then evaporated under vacuum to afford the crude product. This was purified by recrystallization from EtOAc giving pale yellow prismatic crystals on slow evaporation of the solvent (yield 72%). M.p. 397 -399 K. Spectroscopic data for the title compound are given in the archived CIF.

Refinement
All the H atoms were positioned geometrically and refined using a riding model:

Figure 1
The molecular structure of the title molecule, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level.  A view along the a axis of the crystal packing of the title compound. Hydrogen bonds are shown as dashed lines (see Table 1 for details).   3,116.2,123.4,123.8,125.8,127.5,127.7,129.4,130.0,130.1,140.3,148.1,151.1,159.5 (aromatic carbon),. MS m/z = 472 [M + ]. 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.

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