2-Trifluoromethyl-10H-benzo[4,5]imidazo[1,2-a]pyrimidin-4-one

In the molecule of the title compound, C11H6F3N3O, the three fused rings of the benzo[4,5]imidazo[1,2-a]pyrimidine unit are essentially coplanar, the maximum deviation from the mean plane being 0.096 (2) Å. In the crystal, N—H⋯O hydrogen bonds link the molecules into chains running along the b-axis direction.

In the molecule of the title compound, C 11 H 6 F 3 N 3 O, the three fused rings of the benzo [4,5]imidazo[1,2-a]pyrimidine unit are essentially coplanar, the maximum deviation from the mean plane being 0.096 (2) Å . In the crystal, N-HÁ Á ÁO hydrogen bonds link the molecules into chains running along the b-axis direction.
Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009) Benzo[4,5]imidazo[1,2-a]pyrimidin-4-one is a class of fused tricyclic system having three nitrogen atoms. The derivatives of benzopyrimidine are of great importance because of their remarkable biological properties. Some of them have shown good antineoplastic (Abdel-Hafez, 2007) and protein kinase inhibitor (Nunes, Zhu, Amouzegh et al., 2005) activities. Also, heterocycles containing an imidazolone moiety exhibits various biological activities such as antibacterial and antifungal activities (Palacios et al., 2007and Duval et al., 2005, Teimouria et al., 2006. In view of its extensive background, the title compound was prepared and characterized by single-crystal X-ray diffraction. In the molecular structure of the title compound ( Fig. 1), the bond lengths and angles are generally within normal ranges (Allen et al., 1987). The three fused rings of the benzo [4,5]imidazo[1,2-a]pyrimidine unit are essentially coplanar, the maximum deviation from the mean plane being 0.096 (2) Å for atom O15. The crystal structure is stabilized by an intramolecular C-H···O and intermolecular N-H···O hydrogen bonds. The packing diagram of the molecule exhibits linear chain when viewed down the c axis as shown in Fig. 2.

Experimental
An equimolar mixture of 2-aminobenzimadzole (0.5 g, 3.75 mmol) and 4,4,4-Trifluoro-3-oxo-butyric acid ethyl ester (0.69 g, 3.75 mmol) in DMF (10 ml) were added to a microwave tube equipped with a magnetic stir bar. The microwave tube was fitted with a reflux condenser and irradiated in a microwave reactor at a temperature of 130°C for 3 min at a maximum power of 320 W. Then, the reaction mixture was poured on to crushed ice. The solid was filtered and washed with 100 ml of cold water. The crude product was dried and recrystallized from 1:3 ethyl acetate and chloroform to get title compound (Yield = 74%, MP = 223-225°C).

Refinement
H atoms were placed at idealized positions and allowed to ride on their parent atoms with C-H and N-H distances equal to 0.93 and 0.86 Å, respectively. U iso (H) = 1.2-1.5U eq (carrier atom) for all H atoms.

2-Trifluoromethyl-10H-benzo[4,5]imidazo[1,2-a]pyrimidin-4-one
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.42 e Å −3 Δρ min = −0.37 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), FC * =KFC[1+0.001XFC 2 Λ 3 /SIN(2Θ)] -1/4 Extinction coefficient: 0.0057 (9) Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq