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

In the title compound, C10H12N2S, the thiophene ring is essentially planar (r.m.s. deviation = 0.0290 Å). The two C atoms of the cyclohexene ring (at positions 6 and 7) are disordered over two sets of sites in a 0.810 (5):0.190 (5) ratio. The cyclohexene rings in both the major and minor occupancy conformers adopt a half-chair conformation. In the crystal, there are two types of N—H⋯N interaction. One of these results in centrosymmetric head-to-head dimers corresponding to an R 2 2(12) graph-set motif and the other forms a 20-membered macrocyclic ring involving six molecules.

In the title compound, C 10 H 12 N 2 S, the thiophene ring is essentially planar (r.m.s. deviation = 0.0290 Å ). The two C atoms of the cyclohexene ring (at positions 6 and 7) are disordered over two sets of sites in a 0.810 (5):0.190 (5) ratio. The cyclohexene rings in both the major and minor occupancy conformers adopt a half-chair conformation. In the crystal, there are two types of N-HÁ Á ÁN interaction. One of these results in centrosymmetric head-to-head dimers corresponding to an R 2 2 (12) graph-set motif and the other forms a 20-membered macrocyclic ring involving six molecules.
IMK is grateful to the University Grants Commission (UGC), India, for financial assistance.

Khazi Comment
Tetrahydro-benzothiophenes are important class of compounds which exhibits antibacterial and antifungal activities (Shetty et al.,2009). In the title compound, the tetrahydro-benzothiophene ring is substituted with the methyl group at C8, amine at C2 and carbonitrile group at C3 positions. The thiophene ring is essentially planar (r.m.s. deviation = 0.03 Å).
The atoms C6 and C7 are disordered over two sites (C6/C6′ and C7/C7′) with site occupancy factors 0.810 (5) and 0.190 (5) resulting in a major and a minor conformers, respectively. The cyclohexene ring in both the conformers is in the half-chair conformation with C6 and C7 atoms being deviated from the rest of the ring atoms by 0.3330 (3) and -0.3132 (3) Å for the major conformer. The C6′ and C7′ atoms are deviated by -0.3738 (2) and 0.3546 (2) Å for the minor conformer respectively. The methyl group of the cyclohexene ring is oriented axially which is characterized by the bond angles C6-C8-C11 = 112.50 (2)° and C10-C8-C11 = 115.02 (2)°. The crystal structure is stabilized by two types of N-H···N intermolecular interactions generating centrosymmetric head-to-head dimers corresponding to graph-set R 2 2 (12) motif (Bernstein et al., 1995) and a 20-membered macrocyclic ring involving six molecules (Fig. 2). The bond distances and angles in the title compound agree very well with the corresponding bond distances and angles reported in a closely related compound (Ziaulla et al., 2011).

Experimental
To a well stirred mixture of 2-methyl cyclohexanone (8 g, 71.4 mmole) and malononitrile (4.712 g, 71.4 mmole) in ethanol (100 ml) was added elemental sulfur (2.3 g, 72 mmole). To this cooled reaction mixture was added diethyl amine (5 ml) with vigorous stirring during 1 min. The reaction mixture was stirred at 333 K for about 1 h. The solvent was evaporated under reduced pressure. The residue was poured into crushed ice and the solid obtained was purified by column chromatography (yield = 9.3 g (68%), m.p. = 392-394 K. The crystals suitable for X-ray crystallographic analysis were grown from a solution of dichloromethane.

Refinement
The occupancies were refined individually for the C atoms C6 and C7, the disordered atoms were grouped in Part 1 and Part 2 as Part 1: C6 and C7 with partial occupancy of 0.810 (5) and Part 2: C6′ and C7′ with partial occupancy 0.190 (5).
In this way the occupancy disordered was modelled using the EADP command in SHELXL97. The H atoms were placed at calculated positions in the riding model approximation with N-H = 0.86° A, C-H = 0.97 and 0.96 Å for heterocyclic and methyl H atoms respectively, with U iso (H) = 1.5U eq (C) for methyl H atoms and U iso (H) = 1.2U eq (N/C).

Figure 1
The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms are presented as small spheres of arbitrary radius. C6 and C7 are disordered over sites C6/C6′ and C7/C7′ respectively.

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. 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 > 2σ(F 2 ) is used only for calculating R-factors(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.