Ethyl 4-(tert-butylamino)-3-nitrobenzoate

In the title compound, C13H18N2O4, intramolecular N—H⋯O, N—H⋯N and C—H⋯O (× 3) hydrogen bonds generate S(6) and S(5) ring motifs. There are two crystallographically independent molecules (A and B) in the asymmetric unit. The nitro group is coplanar with the benzene ring, with O—N—C—C torsion angles of −0.33 (13) and 0.93 (14)° in molecules A and B, respectively. In the crystal structure, neighbouring molecules are linked together by intermolecular C—H⋯O hydrogen bonds. In addition, the crystal structure is stabilized by π–π interactions with centroid–centroid distances ranging from 3.7853 (6) to 3.8625 (6) Å.

In the title compound, C 13 H 18 N 2 O 4 , intramolecular N-HÁ Á ÁO, N-HÁ Á ÁN and C-HÁ Á ÁO (Â 3) hydrogen bonds generate S(6) and S(5) ring motifs. There are two crystallographically independent molecules (A and B) in the asymmetric unit. The nitro group is coplanar with the benzene ring, with O-N-C-C torsion angles of À0.33 (13) and 0.93 (14) in molecules A and B, respectively. In the crystal structure, neighbouring molecules are linked together by intermolecular C-HÁ Á ÁO hydrogen bonds. In addition, the crystal structure is stabilized byinteractions with centroid-centroid distances ranging from 3.7853 (6) to 3.8625 (6) Å .

Comment
As a part of our ongoing studies on new nitro benzoic acid derivatives, we have synthesized the title compound (I) employing a modified protocol of previous procedure (Göker et al., 1998). The nitro benzoic acid intermediates are a convenient starting material for the synthesis of heterocycles targeting important biological processes, e.g. antifungal (Fluconazole) (Anderson, 2005) and proton pump inhibitor (Omeprazole) (Kakei et al., 1993). The crystal structure of the tert-butylamino functionalized nitro benzoic acid (I) has been determined, and herein, we present a full report on its crystal structure.
In the title compound (I) (Fig. 1), intramolecular N-H···O (x 2), N-H···N (x 2), and C-H···O (x 3) hydrogen bonds (Table 2) generate S(6) and S(5) ring motifs, respectively (Bernstein et al., 1995). There are two crystallographically independent molecules, A and B in the asymmetric unit of the title compound. The nitro group is coplanar with the benzene ring with torsion angle of -0.33 (13) and 0.93 (14)° in the molecule A and B, respectively. In the crystal structure neighbouring molecules are linked together by intermolecular C-H···O hydrogen bonds (Table 1). In the crystal packing (Table 2 & Fig. 2), molecules are stacked down the b axis, being consolidated by π-π interactions with centroid to centroid distances ranging from 3.7853 (6) -3.8625 (6) Å.

Experimental
Ethyl 4-fluoro-3-nitrobenzoate (200 mg, 0.93 mmol) was dissolved in dry dichloromethane (10 ml). N, N-diisopropylethylamine (DIPEA) (0.20 ml, 1.12 mmol) was added to the stirred mixture. Then, tert-butylamine (0.11 ml, 1.03 mmol) was added dropwise using syringe and stirred at room temperature under N 2 overnight. After completion of the reaction, the mixture was washed with 10% NaCO 3 (10 ml). The aqueous layer was washed with dichloromethane (3 x 15 ml). The organic layers were collected and dried over MgSO 4 (anhydrous). The solvent was removed under reduced pressure to yield the crude product. Recrystallisation with hot hexane revealed the title compound (I) as bright yellow crystals.

Refinement
The H-atoms attached to N2A and N2B were located from the difference Fourier map and refined as riding with the parent atom with an isotropic thermal parameter 1.2 times that of the parent atom. The rest of the hydrogen atoms were positioned geometrically [C-H = 0.95-98 Å] and refined using a riding model. A rotating-group model was used for the methyl groups. The highest peak is located 0.63 Å from C6B and the deepest hole is located 0.59 Å from N1A. Ethyl 4-(tert-butylamino)-3-nitrobenzoate