6-Methyl-3-phenyl-2-sulfanylidene-1,2,3,4-tetrahydroquinazolin-4-one

The title compound, C15H12N2OS, exists as the thione tautomer in the solid state. The phenyl group is almost perpendicular [dihedral angle = 87.96 (5)°] to the fused ring system (r.m.s. deviation = 0.036 Å for 13 ring and exocyclic non-H atoms). In the crystal, centrosymmetric dimers, sustained by pairs of N—H⋯S hydrogen bonds, are connected into layers parallel to (-101) by C—H⋯O and C—H⋯S interactions.

The title compound, C 15 H 12 N 2 OS, exists as the thione tautomer in the solid state. The phenyl group is almost perpendicular [dihedral angle = 87.96 (5) ] to the fused ring system (r.m.s. deviation = 0.036 Å for 13 ring and exocyclic non-H atoms). In the crystal, centrosymmetric dimers, sustained by pairs of N-HÁ Á ÁS hydrogen bonds, are connected into layers parallel to (101) by C-HÁ Á ÁO and C-HÁ Á ÁS interactions.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: QM2054).  et al. (2011, 2010). The title compound (I) has been investigated previously for its anti-microbial activity (Al-Omar et al., 2004). Herein, its crystal and molecular structure is described.

6-Methyl
The key result of the crystal structure determination of (I), Fig. 1, is the confirmation that the compound exists as the thione tautomer in the solid-state. The non-hydrogen atoms comprising the fused ring system, including the exocyclic atoms, are co-planar with a r.m.s. deviation = 0.036 Å. The maximum deviations from the least-squares plane through these atoms are 0.038 (1) Å for the S1 atom and -0.085 (1) Å for N1, consistent with some pyramidal character for the latter atom. The phenyl group is almost perpendicular to the aforementioned plane: the dihedral angle = 87.96 (5)°.
The presence of the thione tautomer confirms the results of previous structure determinations on related compounds (Bowman et al., 2007;Hashim et al., 2010).
The key feature of the crystal packing is the formation of N-H···S hydrogen bonds between centrosymmetrically related molecules, Table 1. The dimeric aggregates thus formed are connected into layers parallel to (1 0 1) by C-H···O interactions, involving the bifurcated carbonyl-O atom, and C-H···S interactions, Fig. 2 and Table 1. Layers stack with no specific intermolecular interactions between them, Fig. 3.

Refinement
Carbon-bound H-atoms were placed in calculated positions [C-H = 0.95 to 0.98 Å, U iso (H) = 1.2 to 1.5U eq (C)] and were included in the refinement in the riding model approximation. The N-H atom was located in a difference Fourier map, and was refined with distance restraint of N-H = 0.88±0.01 Å; the U iso value was refined.

Figure 1
The molecular structure of (I) showing the atom-labelling scheme and displacement ellipsoids at the 50% probability level.  A view in projection down the b axis of the unit-cell contents of (I). The N-H···S, C-H···O and C-H···S interactions are shown as blue, orange and brown dashed lines, respectively. 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 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.