(E)-Methyl N′-(3,4-dimethoxybenzylidene)hydrazinecarboxylate

The title compound, C11H14N2O4, crystallizes with two independent but essentially identical molecules in the asymmetric unit. Each molecule adopts a trans configuration with respect to the C=N bond. Molecules are linked into a one-dimensional network by inter- and intramolecular N—H⋯O and C—H⋯O hydrogen bonds.


Comment
Benzaldehydehydrazone derivatives have received considerable attentions for a long time due to their pharmacological activity (Parashar et al., 1988) and their photochromic properties (Hadjoudis et al., 1987). Meanwhile, it's an important intermidiate of 1,3,4-oxadiazoles, which have been reported to be versatile compounds with many properties (Borg et al., 1999). As a further investigation of this type of derivatives, we report herein the crystal structure of the title compound (I).
The title compound, C 11 H 14 N 2 O 4 ,crystallizes with two independent, but essentially identical molecules in the asymmetric unit. Each essentially planar molecule of the unit adopts a trans configuration with respect to the C═N bond. in a molecule of the unit,the hydrazine carboxylic acid methyl ester group is slightly twisted away from the attached ring. The dihedral angle between the two essentially planar molecule of the unit is 81.67 (4)°. The bond lengths and angles agree with those observed for (E)-Methyl N'-(4-hydroxybenzylidene)hydrazinecarboxylate (Shang et al., 2007).
The molecules are linked into a one-dimensional network by intermolecular intramolecular N-H···O, C-H···O hydrogen bonds (Fig.2). Meanwhile, A C-H···π contact between benzene ring (centroid Cg1) and H atom of methoxy C13 further stabilizes the structure (Table 1).
Experimental 3,4-Dimethoxybenzaldehyde (1.66 g, 0.01 mol) and methyl hydrazinecarboxylate (0.9g, 0.01mol) were dissolved in stirred methanol (25ml) and left for 3.2h at room temperature. The resulting solid was filtered off and recrystallized from ethanol to give the title compound in 86% yield. Crystals suitable for X-ray analysis were obtained by slow evaporation of a ethanol solution at room temperature (m.p. 468-470 K).

Refinement
H atoms were included in the riding model approximation with N-H = 0.86Å. C-bound H atoms were positioned geometrically (C-H = 0.93Å and 0.96Å) and refined using a riding model, with U iso (H) = 1.2-1.5U eq (C). In the absence of significant anomalous dispersion effects, Friedel pairs were averaged.

Special details
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.