(E)-N’-(2,3,4-Trimethoxybenzylidene)isonicotinohydrazide

In the title compound, C16H17N3O4, the molecule exists in an E configuration with respect to the C=N double bond. The molecule is not planar, the dihedral angle between the pyridine and benzene rings being 71.67 (8)°. In the crystal structure, molecules are linked into chains along the b axis by bifurcated N—H⋯O and C—H⋯O hydrogen bonds. These chains are linked into a three-dimensional network by C—H⋯O and C—H⋯π interactions.

In the title compound, C 16 H 17 N 3 O 4 , the molecule exists in an E configuration with respect to the C N double bond. The molecule is not planar, the dihedral angle between the pyridine and benzene rings being 71.67 (8) . In the crystal structure, molecules are linked into chains along the b axis by bifurcated N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds. These chains are linked into a three-dimensional network by C-HÁ Á ÁO and C-HÁ Á Á interactions.

Comment
In the search of new compounds of pharmaceutical importance, isoniazid derivatives have been found to possess potential tuberculostatic activity (Janin, 2007;Maccari et al., 2005;Slayden & Barry, 2000). Schiff bases have attracted much attention because of their biological activity (Kahwa et al., 1986). As a part of on-going work into the synthesis of (E)-N'-substituted isonicotinohydrazide derivatives, in this paper we present the crystal structure of the title compound (I).

Experimental
The isoniazid derivative (I) was prepared following the procedure by Lourenco et al. (2008). 2,3,4-Trimethoxybenzaldehyde (1.0 eq) was reacted with isoniazid (1.0 eq) in ethanol/water. After stirring for 3 h at room temperature, the resulting mixture was concentrated under reduced pressure. The residue was purified by washing with cold ethanol and ethyl ether, affording the pure derivative. The colourless crystals were obtained by recrystallization from a methanol solution of (I).

Refinement
The H1N2 H atom was located from a difference Fourier map and refined freely. The remaining H atoms were positioned geometrically [C-H = 0.93 or 0.96 Å] and refined using a riding model, with U iso (H) = 1.2 or 1.5 U eq (C). A rotating-group model was applied for the methyl groups. Fig. 1. The molecular structure of (I) with atom labels and 50% probability ellipsoids for non-H atoms.
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.