Methyl 5-(4-acetoxyphenyl)-2-(2-bromobenzylidine)-7-methyl-3-oxo-2,3-dihydro-5H-1,3-thiazolo[3,2-a]pyrimidine-6-carboxylate

In the title molecule, C24H19BrN2O5S, the pyrimidine ring is in a flattened half-chair conformation and the 4-acetoxyphenyl group is substituted axially to this ring. The thiazole ring is essentially planar [with a maximum deviation of 0.012 (2) Å for the N atom] and forms dihedral angles of 17.65 (13) and 88.95 (11)° with the bromo- and acetoxy-substituted benzene rings, respectively. The dihedral angle between the benzene rings is 81.84 (13) Å. In the crystal, pairs of weak C—H⋯O hydrogen bonds lead to the formation of inversion dimers. A weak C—H⋯π interaction and π–π stacking interactions with centroid–centroid distances of 3.5903 (14) Å are observed.

In the title molecule, C 24 H 19 BrN 2 O 5 S, the pyrimidine ring is in a flattened half-chair conformation and the 4-acetoxyphenyl group is substituted axially to this ring. The thiazole ring is essentially planar [with a maximum deviation of 0.012 (2) Å for the N atom] and forms dihedral angles of 17.65 (13) and 88.95 (11) with the bromo-and acetoxy-substituted benzene rings, respectively. The dihedral angle between the benzene rings is 81.84 (13) Å . In the crystal, pairs of weak C-HÁ Á ÁO hydrogen bonds lead to the formation of inversion dimers. A weak C-HÁ Á Á interaction andstacking interactions with centroid-centroid distances of 3.5903 (14) Å are observed.
NSB is thankful to the University Grants Commission (UGC), India, for financial assistance. These non-planar heterocyclic compounds have interesting multifaceted pharmacological profiles such as calcium channel modulation, antitumor, antiviral, antibacterial, anti-inflammatory and antimicrobial activities (Kappe et al., 2000;Atwal et al.. 1991). In addition, a few DHPM derivatives have even emerged as orally active antihypertensive agents (Rovnyak et al., 1992).
The molecular structure of the title compound is shown in Fig. 1. The 4-acetoxy substituted benzene ring is axially substituted to the pyrimidine ring. The central pyrimidine ring adopts a half chair conformation with deviations of 0.107 (2) and -0.200 (2) Å for N1 and C5 respectively from the remaining four ring atoms (C6/C7/C9/N2). In the crystal, pairs of weak C-H···O hydrogen bonds form inversion dimers with a graph set notation of R 2 2 (16) (Bernstein et al., 1995) as shown in Fig. 2. The crystal structure of the title compound shows different type of intermolecular interactions compared to a similar structure reported earlier (Nagarajaiah et al., 2012). In addition, there are intermolecular π···π interactions between inversion-related thiazole rings with a centroid to centroid distance of 3.5903 (14)Å. A weak C-H···π(ring) interaction is also observed (see Table 1, where Cg is the centroid of the C5/C6/C7/N2/C9/N1 ring). Another example of a related crystal structure has been published in the literature (Nagarajaiah et al., 2011).

Refinement
The H atoms were placed in calculated positions in a riding-model approximation with C-H = 0.93 Å, 0.96 Å and 0.98 Å for aryl, methyl and methyne H-atoms respectively, with U iso (H) = 1.5U eq (C) for methyl H atoms and U iso (H) = 1.2U eq (C) for other H atoms.

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.