Crystal structure of 1,7,8,9-tetrachloro-4-(2-fluorobenzyl)-10,10-dimethoxy-4-azatricyclo[5.2.1.02,6]dec-8-ene-3,5-dione

In the title compound, C17H12Cl4FNO4, the configuration of the cycloalkene skeleton is endo,cis. The benzene ring is twisted by 71.01 (11)° from the attached pyrrolidine ring. In the crystal, one of the methine groups of the fused-ring system forms a weak C—H⋯O hydrogen bond. The other methine groups participates in a C—H⋯F interaction to the same adjacent molecule. Together, these generate [010] chains.

The fused pyrrolidine ring systems, are frequently encountered structural units in many synthetically challenging and biologically active alkaloids. The interest of constructing skeletons of this type was further enlightened by the recent disclosure of Kossakowski et al., (2006) that the rigid arylcyclo analogues having azatricyclo ring systems show anti-HIV-1, anti-cancer, antiviral, and antibacterial activities. We have synthesized a serial compounds with this cycloalkene skeleton. This report is one of them.
In the crystal structure, there is a tricyclic fused pyrrolidine ring system. The configuration of the cycloalkene skeleton is endo, cis. The dihedral angle of pyrrolidine ring and benzene ring is 71.01 (11)°.
The molecules packed in spacegroup P2 1 2 1 2 1 , and the absolute configuration of the title compound can be determined from Flack parameter x=-0.02 (7), and the compound has chirality at C1S, C2S, C6R, C7R.
These pairs of H-bonds link the neighbour molecules along baxis to form infinite chains. Another two molecules in the unit cell along baxis linked by the same weak H-bonds in the opposite direction. So the whole crystal packing exists as countless helices along baxis.
Then the solution was refluxed for 8 h. After the solvent was removed under reduced pressure, the residue was dissolved in ether (150 mL), washed with water and brine, dried over anhydrous sodium sulfate, and concentrated to dryness. The product was purified by flash-chromatography (petroleum ether/ethyl acetate, 6:1) and the title compound was isolated as a white solid (3.86 g, 85%). m.p.: 116-118°C.
The crystals appropriate for X-ray data collection were obtained from ethyl acetate solution at room temperature after two days.

S3. Refinement
All H atoms were placed in geometically idealized positions and constrained to ride on their parent atoms with C-H distances of 0.93 Å (0.98 for alicylic CH) for aromatic ring CH, and U iso (H) = 1.2(1.5 for CH 3 )U eq (C).

Figure 1
View of the molecule of (I) showing displacement ellipsoids drawn at the 30% probability level.

Figure 2
The C-H···X(X=O/F) interactions, dashed lines. Non-essential H atoms are omitted for clarity. Symmetry code: (i) 1 -x, where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.28 e Å −3 Δρ min = −0.26 e Å −3 Absolute structure: Flack (1983), 1826 Friedel pairs Absolute structure parameter: −0.02 (7) 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.