7-Methyl-5,6,7,8-tetrahydro-1-benzothieno[2,3-d]pyrimidin-4-amine

In the title compound, C11H13N3S, two of the C atoms of the cyclohexene ring and the methyl group attached to it are disordered over two sets of sites in a 0.544 (2):0.456 (2) ratio. The benzothiene and pyrimidine rings are almost coplanar with an angular tilt of 2.371 (9)° between them. The thiophene ring is essentially planar (r.m.s. deviation 0.05 Å), while the cyclohexene ring in both the major- and minor-occupancy conformers adopts a half-chair conformation. In the crystal structure, pairs of intermolecular N—H⋯N hydrogen bonds involving the amino groups result in centrosymmetric head-to-head dimers about inversion centres, corresponding to an R 2 2(8) graph-set motif. Further, N—H⋯N hydrogen bonding generates a two-dimensional hydrogen-bonded network perpendicular to the ac plane and running along the diagonal of the ac plane.

In the title compound, C 11 H 13 N 3 S, two of the C atoms of the cyclohexene ring and the methyl group attached to it are disordered over two sets of sites in a 0.544 (2):0.456 (2) ratio. The benzothiene and pyrimidine rings are almost coplanar with an angular tilt of 2.371 (9) between them. The thiophene ring is essentially planar (r.m.s. deviation 0.05 Å ), while the cyclohexene ring in both the major-and minor-occupancy conformers adopts a half-chair conformation. In the crystal structure, pairs of intermolecular N-HÁ Á ÁN hydrogen bonds involving the amino groups result in centrosymmetric head-tohead dimers about inversion centres, corresponding to an R 2 2 (8) graph-set motif. Further, N-HÁ Á ÁN hydrogen bonding generates a two-dimensional hydrogen-bonded network perpendicular to the ac plane and running along the diagonal of the ac plane.
NSB is grateful to the University Grants Commission (UGC), India, for financial assistance, and to 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: DS2116).

Comment
The pyrimidine ring is a frequent partner in polycyclic heterocyclic systems of biological significance (Brown, 1983). Many potential drugs have been modelled on these compounds, particularly in cancer and virus research (Heildelberg & Arafield, 1963;De Clercq, 1986a,b). These derivatives have been reported to possess analgesic, antipyretic, antianaphilactic and antiinflammatory activities. Also, some are clinically effective antiallergic, potentially antineoplastic agents, or have significant hypocholesterolemic activity (Sishoo et al., 1983). In the title compound, the fused Benzothieno and pyrimidine rings are substituted with amino and methyl groups. The C atoms C6, C7 and C11 are disordered over two sites (C6A/C6B, C7A/C7B and C11A/C11B) with site occupancy factors 0.544 (2) and 0.456 (2) resulting in minor and major conformers.
The thiophene ring is essentially planar. The cyclohexene rings in both conformers is in a half-chair conformation with C7A and C7B 0.549 (4) and 0.506 (6) Å, respectively, displaced on the opposite sides from the plane formed by the rest of the ring C-atoms. In several benzothiophene derivatives the cyclohexyl ring adopts half-chair conformation (Akkurt et al., 2008;Harrison et al., 2006). The crystal structure is stabilized by two types of N-H···N intermolecular interactions (Table 1); N1-H1A···N2 hydrogen bonds forms centrosymmetric head-to-head dimers about inversion centres, corresponding to an R 2 2 (8) graph-set motif (Bernstein et al., 1995) while C7A-H7A···N2 hydrogen bonds generates two-dimensional hydrogen bonded network perpendicular to ac plane and running along the diagonal of ac plane (Fig. 2).

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