endo,endo-Tetracyclo[6.2.1.13,6.02,7]dodeca-9-en-anti-11-yl 4-bromobenzoate

The title compound 1-OPBB, C19H19BrO2, contains a dechlorinated and hydrogenated isodrin backbone with an anti-4-bromobenzoate substituent at one of the methano bridges. The dihedral angle between the CO2 ester plane and the benzene ring plane is 8.5 (2)°. In the crystal, the ester groups stack over benzene rings: the molecules pack as conformational enantiomers, with nearest parallel benzene ring planes separated by a perpendicular distance of 3.339 (1) Å. The nearest benzene-ring centroids are 5.266 (1) Å apart. Possible structural correlation with enhanced solvolytic reactivity is investigated.

The title compound 1-OPBB, C 19 H 19 BrO 2 , contains a dechlorinated and hydrogenated isodrin backbone with an anti-4-bromobenzoate substituent at one of the methano bridges. The dihedral angle between the CO 2 ester plane and the benzene ring plane is 8.5 (2) . In the crystal, the ester groups stack over benzene rings: the molecules pack as conformational enantiomers, with nearest parallel benzene ring planes separated by a perpendicular distance of 3.339 (1) Å . The nearest benzene-ring centroids are 5.266 (1) Å apart. Possible structural correlation with enhanced solvolytic reactivity is investigated.

Experimental
Compound 1-OPBB was synthesized via the steps shown in Fig. 4 and described below. Products were verified by 90 MHz 1 H NMR spectroscopy in CDCl 3 solvent. The most recent methods for synthesizing precursor compound 6 are found in Chow (1996). See also Melder & Prinzbach (1991) for substrate syntheses.
Into 70 ml of CH 2 Cl 2 were dissolved 2.0 g of 6 and 0.1 g of 10% Pd/C was added. The mixture was stirred under H 2 (~9 × 10 4 Pa) at 298 K for 12 h. The mixture was vacuum filtered to remove catalyst, and CH 2 Cl 2 was removed under Into 5 ml of freshly distilled dry pyridine (from CaH 2 ) were dissolved 0.086 g of pure 1-OH, and 0.14 g of freshly recrystallized (from hexanes) 4-bromobenzoyl chloride with stirring under a dry N 2 atmosphere. The mixture was warmed briefly until reagents dissolved, and stirred overnight at 298 K. The mixture was poured into 100 ml of cold water, and extracted with 2 × 50 ml of ether. Combined ether extracts were washed with water, twice with 10% HCl, twice with NaHCO 3 , and with saturated brine. The ether solution was dried over MgSO 4 , filtered, and ether was evaporated under vacuum, yielding crude 1-OPBB. Recrystallization from a 1:4 CHCl 3 / hexane mixture yielded 0.15 g (86%) of white 1-OPBB crystals. These were dissolved in ~5 ml of CH 2 Cl 2 and passed down a 0.05 m × 0.005 m silica gel column, eluting with distilled CH 2 Cl 2 , and solvent was evaporated. The residual white crystals were sublimed (353 K, About 0.1 g of sublimed 1-OPBB was dissolved in 15 ml of absolute ethanol by warming on a steam bath for 5 min.
This solution was placed in a crystallizing dish and covered with plastic wrap. Three small holes were made in the plastic wrap with a hot wire and ethanol slowly evaporated at 298 K. About ten crystals were eventually removed from the evaporating dish, and one of these was selected for the X-ray structure analysis.

Refinement
A colorless plate shaped crystal 0.23 × 0.20 × 0.13 mm in size was mounted on a quartz fiber with epoxy resin, and transferred to a Nonius KappaCCD diffractometer equipped with Mo Kα radiation (λ = 0.71073 Å). Ten frames of data were collected at 150 (1) K with an oscillation range of 1°/frame and an exposure time of 20 sec/frame (Nonius, 1998).
Indexing and unit cell refinement based on all observed reflections from those ten frames indicated a monoclinic P lattice.

Special details
Experimental. The program DENZO-SMN (Otwinowski & Minor, 1997) uses a scaling algorithm which effectively corrects for absorption effects. High redundancy data were used in the scaling program hence the 'multi-scan′ code word was used. No transmission coefficients are available from the program (only scale factors for each frame). The scale factors in the experimental table are calculated from the 'size′ command in the SHELXL-97 input file. 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 >σ2(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.  (7)  C7 0.0243 (9) 0.0181 (9) 0.0188 (9) −0.0002 (7) 0.0101 (7) 0.0029 (7)  0.0138 (9) 0.0263 (10) 0.0183 (9) −0.0006 (7) 0.0043 (7) 0.0006 (7)  C15 0.0227 (10) 0.0325 (12) 0.0291 (10) 0.0005 (8) 0.0145 (8) −0.0027 (9) C16 0.0248 (10) 0.0340 (12) 0.0308 (11) −0.0016 (9) 0.0167 (9) 0.0047 (9)  C17 0.0190 (9) 0.0261 (10)