(E)-N′-(3-Benzyloxy-4-methoxybenzylidene)isonicotinohydrazide

In the title compound, C21H19N3O3, the pyridine ring forms a dihedral angle of 15.25 (6)° with the benzene ring. The dihedral angle between the two benzene rings is 83.66 (7)°. The methoxy group is slightly twisted away from the attached ring [C—O—C—C = 7.5 (2)°]. In the crystal structure, molecules are linked into a three-dimensional network by intermolecular N—H⋯N and C—H⋯O hydrogen bonds. The structure is further stabilized by C—H⋯π interactions.


Comment
In the search of new compounds, 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 a current work of synthesis of (E)-N'-(substituted-benzylidene) isonicotinohydrazide derivatives, in this paper we present the crystal structure of the title compound.

Experimental
The isoniazid (INH) derivative was prepared following the procedure by literature (Lourenço et al., 2008). (E)-N'-(3-Benzyloxy-4-methoxybenzylidene)isonicotinohydrazide was prepared by reaction between the 3-benzyloxy-4-methoxy benzaldehyde (1.0 eq) with INH (1.0 eq) in ethanol/water (10 ml), initially dissolving the INH in water and adding the respective solution over a solution of the aldehyde in ethanol. After stirring for 1 to 3 h at room temperature, the resulting mixture was concentrated under reduced pressure. The residue was purified by washing with cold ethyl alcohol and ethyl ether to afford the pure derivative. Yellow single crystals suitable for X-ray analysis were obtained by slow evaporation of a dimethyl sulfoxide solution at room temperature.

Refinement
All carbon-bound H atoms were positioned geometrically [C-H = 0.93-0.97 Å] and were 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 group. Atom H1N2 was located in a difference Fourier map and refined freely. Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme.   Glazer, 1986) operating at 100.0 (1) K.

sup-2 Figures
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 > σ(F 2 ) is used only for calculating Rfactors(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.