endo-11-(Dibenzylamino)tetracyclo[5.4.0.03,10.05,9]undecane-8-one

The structure of the title compound, C25H27NO, is a mono-ketone pentacycloundecane (PCU) molecule bearing a tertiary amine group. One of the methylene groups in the PCU is disordered over two orientations with site-occupancy factors of 0.621 (7) and 0.379 (7).

The structure of the title compound, C 25 H 27 NO, is a monoketone pentacycloundecane (PCU) molecule bearing a tertiary amine group. One of the methylene groups in the PCU is disordered over two orientations with site-occupancy factors of 0.621 (7) and 0.379 (7).    10 .0 5,9 ]undecane-8-one R. Karpoormath, P. Govender, T. Govender, H. G. Kruger and G. E. M. Maguire

Comment
We have reported the structures of a number of PCU derivatives including a mono-ketone ethylene acetal (Kruger et al., 2006). We more recently reported the structure of a mono-ketone pentacycloundecane (PCU) (Karpoormath et al. 2010), that demonstrated intramolecular hydrogen bonding, a quite uncommon feature hitherto in mono-ketone PCU structures (Watson et al., 2000). In that example the racemate occupied alternative sites in the unit cell.
Herein, we report the crystal structure of the title compound (Fig. 1). The C1 methylene group in PCU is disordered over two positions with site-occupancy factors of 0.621 (7) (for atom labelled A) and 0.379 (7) (for atom labelled B) in Fig. 1.

Experimental
A solution of PCU cage N-dibenzyl mono ethylene ketal (0.5 g, 1.25 mmol) in 10 ml of THF was stirred at room temperature for 5 minutes. To this mixture was added 10 ml of 10% HCL solution and stirred overnight at room temperature. THF was removed from the crude product under vacuum using a teflon pump at 80 °C to obtain an aqueous solution with white precipitate. The precipitate was collected by vacuum filtration and washed with water (50 ml) to give a white solid. The yield was 97%. Crystallization of the title compound was carried out by dissolving the compound in ethyl acetate and hexane (1:4) with storage at 20 °C. Melting point: 438-439 K. IR (neat) Vmax cm -1 : 3376.61, 2978.73, 2961.26, 2794.11, 1721.74, 1602.42, 1494.57, 1342.20, 1131.34, 752.25, 731.39, 696.73, cm -1

Refinement
All hydrogen atoms were positioned geometrically with C-H = 0.95-1.00 Å and refined as riding on their parent atoms, with U iso (H) = 1.2 U eq (C). The C1 methylene group was found to be disordered over two positions and modelled with site-occupancy factors, from refinement of 0.621 (7) (C1A) and 0.379 (7) (C1B), respectively. The distance of C2-C1A, C6-C1B and C7-C1A and C11-C1B sets were restrained to 0.001 Å using command SADI and DELU. The displacement ellipsoids of C1A and C1B were restrained using commend ISOR (0.01).
supplementary materials sup-2 Figures Fig. 1. The molecular structure of the title compound with atomic numbering scheme. All hydrogen atoms are omitted for clarity. Displacement ellipsoids are drawn at the 25% probability level. The C1 methylene group was found to be disordered over two positions and modelled with site-occupancy factors, from refinement of 0.621 (7) (C1A) and 0.379 (7)
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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.