Ethyl 2-[2-(2-methoxyphenyl)hydrazinylidene]-3-oxobutanoate

In the title compound, C13H16N2O4, an intramolecular N—H⋯O hydrogen bond generates an S(6) ring. The molecule adopts an E configuration with respect to the central C=N double bond. In the crystal, symmetry-related molecules are connected into chains along [010] via weak C—H⋯N hydrogen bonds. The crystal structure is further stabilized by weak C—H⋯π interactions.

In the title compound, C 13 H 16 N 2 O 4 , an intramolecular N-HÁ Á ÁO hydrogen bond generates an S(6) ring. The molecule adopts an E configuration with respect to the central C N double bond. In the crystal, symmetry-related molecules are connected into chains along [010] via weak C-HÁ Á ÁN hydrogen bonds. The crystal structure is further stabilized by weak C-HÁ Á Á interactions.

Experimental
The title compound was prepared by dissolving 2-methoxy aniline (0.01 mol) in dilute hydrochloric acid (10 ml) and cooled to 273K in an ice bath. To this, a cold solution of sodium nitrite (0.02 mol) was added. The resulting diazonium salt solution was filtered into a cold solution of ethyl acetoacetate (0.05 mol) and sodium acetate in ethanol. The separated yellow solid was filtered, washed with water and recrystallized from ethanol. Crystals suitable for X-ray analysis were obtained by slow evaporationfrom of a solution of (I) in a 1:2 mixture of DMF and ethanol.

Refinement
Atom H1N1 was located in a difference Fourier map and refined freely [N-H = 0.898 (17)

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
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 > 2sigma(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.