4-(4-Bromophenyl)-5-oxo-1,2,3,4,5,6,7,8-octahydroquinazoline-2-thione

The title compound, C14H13BrN2OS, was synthesized from the multicomponent reaction between thiourea, 4-bromobenzaldehyde and cyclohexane-1,3-dione. The crystal packing is stabilized by intermolecular N—H⋯O, N—H⋯S, C—H⋯O and C—H⋯S hydrogen bonds. Br⋯O interactions [3.183 (3) Å] are also observed in the crystal structure.

The reaction between thiourea, 4-bromobenzaldehyde, and 1,3-cyclohexanedione instead of an open-chain dicarbonyl compound in the presence of palladium(II) 2,4-pentanedionate as catalyst proceeded to give the title compound in excellent yield. A representation of the title compound is given in Figure 2. There are no unusual bond lengths and angles in the compound. The molecules in the structure are linked via N1-H1···O1 and paired N2-H2···S1 intermolecular hydrogen bonds. The bromine atom Br1 exhibits a Br···O halogen bond with oxygen atom O1 ( Figure 3). (Damodharana et al., 2004;Sureshan et al., 2001;Yang et al., 2008). The Br1···O1 distance of this interaction is 3.182 Å, which is less than the sum of their van der Waals radii.

Experimental
A mixture of thiourea (0.91 g, 12 mmol), 4-bromobenzaldehyde (1.84 g, 10 mmol), 1,3-cyclohexanedione (1.12 g, 10 mmol), and palladium(II) 2,4-pentanedionate (0.0020 mg) was refluxed in acetonitrile (12 ml) at 353 K for 4 h. After being cooled to room temperature, the reaction mixture was poured into water. The white precipitate was filtered off with a silica pad, washed twice with water, and the filtrate was then dried under vacuum to yield the product. Single crystals of the title compound were obtained by slow evaporation from ethanol at room temperature to yield colourless, block-shaped crystal.

Refinement
The H atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.93-0.97 Å and N-H = 0.86 Å, respectively, and U iso = 1.2 eq (parent atom).

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