Ethyl 3-nitro-4-(propylamino)benzoate

In the title compound, C12H16N2O4, intramolecular N—H⋯O and C—H⋯O hydrogen bonds generate S(6) and S(5) ring motifs, respectively. The nitro group is almost coplanar with the benzene ring, forming a dihedral angle of 6.2 (2)°. In the crystal structure, neighbouring molecules are linked together by intermolecular N—H⋯O and O⋯O interactions. Of interest are the short intermolecular O⋯O interactions which cause a stacking arrangement of the molecules along the a axis.

In the title compound, C 12 H 16 N 2 O 4 , intramolecular N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds generate S(6) and S(5) ring motifs, respectively. The nitro group is almost coplanar with the benzene ring, forming a dihedral angle of 6.2 (2) . In the crystal structure, neighbouring molecules are linked together by intermolecular N-HÁ Á ÁO and OÁ Á ÁO interactions. Of interest are the short intermolecular OÁ Á ÁO interactions which cause a stacking arrangement of the molecules along the a axis.

Comment
The benzoic acid cores are precursors to many medicinally important heterocycles, e.g. benzimidazoles (Ishida et al., 2006;Vinodkumar et al., 2008) and benzoxazoles (Rida et al., 2005;Harikrishnan et al., 2008). Using Moore's procedure (Moore et al., 2005) with some modifications, we attempted the derivatization of nitro benzoic acid precursors, which led to the synthesis of the title compound (I) bearing a propylamine motif. Its crystal structure has been determined and is presented here.
In the title compound (I), (Fig. 1), intramolecular N-H···O and C-H···O hydrogen bonds generate S(6) and S(5) ring motifs, respectively (Bernstein et al., 1995). The bond lengths and angles are within normal ranges (Allen et al., 1987).The nitro group is almost coplanar with the benzene ring with torsion angle of -6.4 (5)°. In the crystal structure ( Fig. 2), neighbouring molecules are linked together by intermolecular N-H···O and O···O interactions. The interesting feature of the crystal structure is the short intermolecular O···O [symmetry codes: -x, 1 -y, 1 -z; 1 -x, 1 -y, 1 -z] interactions ( Table   2) with distances of 2.914 (5) and 2.984 (5) Å which are shorter than the sum of the van der Waals radii of oxygen atoms.
These interactions along with the intermolecular N-H···O interactions stack the molecules along the a axis.
After completion of the reaction, the mixture was washed with 10% Na 2 CO 3 (10 ml). The aqueous layer was washed again with dichloromethane (3 x 15 ml). The organic fractions were pooled and dried over MgSO 4 and the solvent was removed by rotary evaporator. Recrystallization with hot hexane afforded the desired compound (I) as yellow needle-like crystals.

Refinement
The H-atom bound to N1 was located from the difference Fourier map and refined freely. The rest of the hydrogen atoms were positioned geometrically [C-H = 0.93-0.97 Å] and refined using a riding model with U iso = 1.2 or 1.5U eq (C). A rotating-group model was used for the methyl groups. sup-2