1-(4,5-Dinitro-10-azatricyclo[6.3.1.02,7]dodeca-2,4,6-trien-10-yl)-2,2,2-trifluoroethanone

In the title compound, C13H10F3N3O5, a derivative of andrographolide, the five-membered ring adopts an envelope conformation, while the non-planar six-membered ring has a chair conformation. An intramolecular C—H⋯F hydrogen bond results in the formation of a non-planar six-membered ring adopting a twisted conformation. In the crystal structure, intermolecular C—H⋯O hydrogen bonds link the molecules into centrosymmetric dimers.


S3. Refinement
H atoms were positioned geometrically, with C-H = 0.93, 0.98 and 0.97 Å for aromatic, methine and methylene H, respectively, and constrained to ride on their parent atoms with U iso (H) = 1.2U eq (C).

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

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å
parameters constrained Á max = 0.33 e A ˚À3 Á min = À0.35 e A ˚À3 andrographolide are important chemical materials.We report herein the crystal structure of the title compound. Acta Cryst. (2008).E64, o2425

Figure 1
Figure 1The molecular structure of the title molecule, with the atom-numbering scheme.Displacement ellipsoids are drawn at the 30% probability level.Hydrogen bond is shown as dashed line.

Figure 2 A
Figure 2 A partial packing diagram of the title compound.Hydrogen bonds are shown as dashed lines.