Ethyl 2-[(E)-4-(dimethylamino)benzylidenehydrazino]-5-nitrobenzoate

The title compound, C18H20N4O4, exists in the E configuration with respect to the C=N bond of the methylidine unit. The dihedral angle between the two benzene rings is 9.01 (6)°. An intramolecular N—H⋯O hydrogen bond involving the benzoate unit generates an S(6) ring motif. In the crystal, the molecules are linked by weak C—H⋯O interactions into infinite chains along the b axis. These chains are further connected into sheets parallel to the ab plane which are stacked approximately along the c axis. A C—H⋯π interaction is also observed.

The title compound, C 18 H 20 N 4 O 4 , exists in the E configuration with respect to the C N bond of the methylidine unit. The dihedral angle between the two benzene rings is 9.01 (6) . An intramolecular N-HÁ Á ÁO hydrogen bond involving the benzoate unit generates an S(6) ring motif. In the crystal, the molecules are linked by weak C-HÁ Á ÁO interactions into infinite chains along the b axis. These chains are further connected into sheets parallel to the ab plane which are stacked approximately along the c axis. A C-HÁ Á Á interaction is also observed.

Comment
Hydrazine is widely used as a reagent in synthetic organic chemistry but is probably most frequently associated with the transformation of carbonyl-containing compounds to the corresponding hydrazones (Paquette, 1995). These are intermediates in the Wolff-Kishner reduction as well as many other reactions of synthetic utility, such as the Barton vinyl iodide preparation (Barton et al., 1962). Hydrazones have been demonstrated to possess antimicrobial, anticonvulsant, analgesic, antiinflammatory, antiplatelet, antitubercular, anticancer and antitumoral activities (Bedia et al., 2006;Rollas et al., 2002;Terzioglu & Gürsoy, 2003). Hydrazones possessing an azometine -NHN=CH-proton constitute an important class of compounds for new drug development. Therefore, many researchers have synthesized these compounds as target structures to evaluate their biological activities. These observations have been the guides for the development of new hydrazones that possess varied biological activities. Some synthesized hydrazide-hydrazones were reported to have lower toxicity than hydrazides because of the blockage of -NH2 group (Buu-Hoi et al., 1953). These findings further support the growing importance of the synthesis of hydrazide-hydrazones compounds. Figure 1 shows the molecular structure of the title compound. The total molecule is not planar and exist in the E configuration with respect to the C═N bond of methylidine moiety. The dihedral angle between the two benzene rings is 9.01 (6)°.

Experimental
The title compound was obtained by refluxing ethyl 2-hydrazinyl-5-nitrobenzoate (0.01 mol) and 4-(dimethylamino) benzaldehyde (0.01 mol) in ethanol (40 ml) by adding 3 drops of concentrated sulfuric acid for 8 hrs. Excess ethanol was removed from the reaction mixture under reduced pressure. The solid product obtained was filtered, washed with water and dried.
Red single crystals of the title compound suitable for x-ray structure determination were grown by slow evaporation of an ethanol solution at room temperature (m.p. 439 K).
supplementary materials sup-2 Refinement H atom attached to N atom was located in a difference map and refined isotropically. The remaining H atoms were constrained in a riding motion approximation, with C aryl -H = 0.93, C methylene -H = 0.97 and C methyl -H = 0.96 Å. The U iso (H) values were constrained to be 1.5U eq of the carrier atom for methyl H atoms and 1.2U eq for the remaining H atoms. A rotating group model was used for the methyl groups. The highest residual electron density peak is located at 0.70 Å from C1 and the deepest hole is located at 0.64 Å from N4. Fig. 1. The asymmetric unit of (I), showing 50% probability displacement ellipsoids and the atomic numbering.