2-Amino-7-oxo-4,5,6,7-tetrahydro-1-benzothiophene-3-carbonitrile

In the title compound, C9H8N2OS, the benzothiophene ring is substituted with amino, oxo and carbonitrile groups. The thiophene ring is essentially planar (r.m.s. deviation = 0.0003 Å), while the cyclohexene ring is in a half-chair conformation. In the crystal, N—H⋯O hydrogen bonds generate chains of molecules in a zigzag pattern along the b axis. Pairs of N—H⋯N hydrogen bonds form centrosymmetric head-to-head dimers about inversion centres, corresponding to an R 2 2(12) graph-set motif. In addition, rather weak N—H⋯S interactions are also present in the structure and the supramolecular assembly is further consolidated by π–π stacking interactions between the benzothiophene rings, disposed at a distance of 3.742 (3) Å.

NSB is grateful to the University Grants Commission (UGC), India, for financial assistance, and the Department of Science and Technology (DST), India, for the data-collection facility under the IRHPA-DST programme.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: PV2326).
The N-H···O hydrogen bonds generate chains of molecules in a zigzag pattern along the b-axis. While the N-H···N hydrogen bonds form centrosymmetric, head-to-head dimers about inversion centers corresponding to graph set R 2 2 (12) motif. In addition, rather weak N-H···S interactions are also present in the structure and the supramolecular assembly is further consolidated by π-π-stacking interactions between the benzothiophene rings; C-C disposed at a distance of 3.742 (3) Å.
The intermolecular interactions of the type N-H···O, N-H···N and N-H···S stabilize the crystal structure (Table   1). The N1-H1A···O1 hydrogen bonds generate chains of molecules in a zigzag pattern along the b-axis (Fig. 2). The N1-H1B···N2 hydrogen bonds on the other hand, form centrosymmetric, head-to-head dimers about inversion centers corresponding to graph set R 2 2 (12) motif (Bernstein et al., 1995) (Fig. 2). In addition, rather weak N1-H1B···S1 interactions are also present in the structure and the supramolecular assembly is further consolidated by π-π-stacking interactions between the benzothiophene rings; C-C disposed at a distance of 3.742 (3) Å.

Experimental
The title compound was synthesized by following the procedure reported earlier (Shetty et al., 2009).

Refinement
The H atoms were placed at calculated positions in the riding model approximation with N-H = 0.86 and C-H = 0.97 Å, and U iso (H) = 1.2U eq (N/C).  Fig. 1. ORTEP (Farrugia, 1997) view of the title compound, showing 50% probability ellipsoids and the atom numbering scheme. 2-Amino-7-oxo-4,5,6,7-tetrahydro-1-benzothiophene-3-carbonitrile 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq C1 −0.0414 (