5-Nitro-1-(prop-2-yn-1-yl)-2,3-dihydro-1H-1,3-benzodiazol-2-one

In the two independent molecules of the title compound, C10H7N3O3, the nitro substitutent is twisted slightly with respect to the benzodiazol fused-ring system [dihedral angles = 4.9 (3) and 8.5 (1)°]. The two independent molecules are disposed about a pseudo inversion center and are held together by N—H⋯O hydrogen bonds. The supramolecular dimer is essentially planar [dihedral angle between the fused rings = 2.0 (1)°]. Adjacent dimers are linked by acetylene–nitro C—H⋯O interactions, generating a ribbon motif along (110).

In the two independent molecules of the title compound, C 10 H 7 N 3 O 3 , the nitro substitutent is twisted slightly with respect to the benzodiazol fused-ring system [dihedral angles = 4.9 (3) and 8.5 (1) ]. The two independent molecules are disposed about a pseudo inversion center and are held together by N-HÁ Á ÁO hydrogen bonds. The supramolecular dimer is essentially planar [dihedral angle between the fused rings = 2.0 (1) ]. Adjacent dimers are linked by acetylenenitro C-HÁ Á ÁO interactions, generating a ribbon motif along (110).

Comment
Benzodiazoles are of interest owing to their pharmacological properties. When the parent compound, benzodiazol-2-one, reacts with propargyl bromide, both amino groups are alkylated to give 1,3-bis(prop-2-ynyl)-benziodiazol-2-one (Ouzidan et al., 2011b). The presence of an electron-withdrawing nitro group allows only one amino group to be alklylated, as noted from the reactions of 5-nitrobenzodiazol-2-onezol with n-octyl bromide and n-nonyl bromide (Ouzidan et al., 2011b(Ouzidan et al., , 2011c. In the two independent molecules of C 10 H 7 N 3 O 3 (Scheme I), the nitro substitutent is slightly bent with respect to the benzodiazol fused-ring (Fig. 2). The two are disposed about a false inversion center, and are held together by N-H···O hydrogen bonds. Adjacent dimers are linked by C-H acetylene ···O nitro interactions to generate a ribbon motif (Fig. 2).

Experimental
To a mixture of 5-nitro-1H-benzodiazol-2(3H)-one (0.25 g, 1.5 mmol), potassium carbonate (0.35 g, 2.5 mmol), tetra-nbutylammonium bromide (0.1 g,0.2 mmol) in DMF (15 ml) was added propargyl bromide (0.14 ml, 1.6 mmol). Stirring was continued at room temperature for 6 hours. The salt was removed by filtration and the filtrate concentrated under reduced pressure. The residue was separated by chromatography on a column of silica gel with ethylacetate/hexane; yellow crystals were obtained upon evaporation of the solvent.

Refinement
All H atoms were located in a difference map. The aromatic and methylene H-atoms were placed in calculated positions (C-H 0.93-0.97 Å) and were included in the refinement in the riding model approximation, with U(H) set to 1.2U(C).
The amino and acetylenic H-atoms were freely refined.
The (0 0 1) reflection was omitted owing to bad disagreement.  Anisotropic displacement ellipsoid plot (Barbour, 2001) of the two independent molecules of C 10 H 7 N 3 O 3 molecule at the 50% probability level; hydrogen atoms are drawn as spheres of arbitrary radius.