(Z)-Ethyl 2-(3-nitrobenzylidene)-3-oxobutanoate

The title molecule, C13H13NO5, adopts a Z conformation at the C= C double bond. The ethoxy atoms of the ethyl ester group are disordered over two orientations in a 3:2 ratio. Weak intermolecular C—H⋯O hydrogen bonds help to establish the packing.

The title molecule, C 13 H 13 NO 5 , adopts a Z conformation at the C C double bond. The ethoxy atoms of the ethyl ester group are disordered over two orientations in a 3:2 ratio. Weak intermolecular C-HÁ Á ÁO hydrogen bonds help to establish the packing.
The molecular structure of the title compound is shown in Fig. 1. It adopts a Z-conformation at the carbon-carbon double bond. The EtO atoms of the ethyl ester group are disordered over two orientations with a ratio 3:2. The molecules are connected mainly by intermolecular C-H···O interactions (Table 1).

S2. Experimental
The title compound was synthesized as previously described by Correa & Scott (2001) via Knoevenagel reaction.
Colourless crystals suitable for X-ray data collection were obtained by slow evaporation of a 2:5 ratio CH 2 Cl 2 :cyclohexane solution at room temperture.

S3. Refinement
All H atoms were positioned geometrically (C-H = 0.93-0.97 Å) and refined as riding, allowing for free rotation of the methyl groups. The constraint U iso (H) = 1.2 U eq (C) or 1.5 U eq (C) (methyl C) was applied.
Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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 > 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.

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