Crystal structure of (1S,3R,8R,9R)-2,2-dichloro-3,7,7-trimethyl-10-methylenetricyclo[6.4.0.01,3]dodecan-9-ol

The title compound was synthesized by treating (1S,3R,8S,9R,10S)-2,2-dichloro-3,7,7,10-tetramethyl-9,10-epoxytricyclo[6.4.0.01,3]dodecane with a concentrated solution of hydrobromic acid. It is built up from three fused rings: a cycloheptane ring, a cyclohexyl ring bearing alkene and hydroxy substituents, and a cyclopropane ring bearing two chlorine atoms.


Structural commentary
There are two molecules A and B within the asymmetric unit, which are built up from three fused rings, a seven-membered heptane ring, a six-membered cyclohexyl ring bearing an hydroxyl and alkene groups and a three-membered propane ring bearing two Cl atoms (Fig. 1). ISSN 2056-9890 In molecule B, there is disorder affecting the location of the C5B, C6B, and C7B atoms, which are split over two positions C5C, C6C, and C7C ( Fig. 2), resulting in disorder of the two methyl atoms attached to C7B and C7C, and also disorder for the two H atoms attached to C5B and C5C. The disordered sites have occupancy factor in the ratio 0.502 (8):0.498 (8). In both molecules, the six-membered ring displays a chair conformation with puckering parameters = 169.3 and ' 2 = 119.6 for molecule A and = 172.1 and ' 2 = 110.0 for molecule B. The seven-membered cycloheptane ring in molecule A displays a conformation intermediate between boat and twist boat with puckering parameters q 2 = 1.138 (4) Å and q 3 = 0.037 (5) Å (Boessenkool & Boeyens, 1980). As a result of the disorder observed in molecule B within the sevenmembered ring, the conformation of this ring is intermediate between chair [q 2 = 0.434 (6), q 3 = 0.739 (6) Å ] or boat and twist-boat [q 2 = 1.173 (5), q 3 = 0.020 (4) Å ] (Boessenkool & Boeyens, 1980), depending on the position of the C6B(C) atom. The disorder does not affect the absolute configuration of the two molecules (1AS,3AR,8AR,9AR) and (1BS,3BR,8BR,9BR).

Supramolecular features
The two independent molecules are connected by O-HÁ Á ÁO hydrogen bonds (Table 1), building a pseudo-dimer. Pairs of such dimers are connected by O-HÁ Á ÁO hydrogen bonds, building an R 4 4(8) cyclic tetramer (Fig. 3). There are also weak C-HÁ Á ÁCl intramolecular interactions (Table 1). The molecular view of the title compound with the atom-labeling scheme. For clarity, only one component of the disorder is represented. Ellipsoids are drawn at the 30% probability level. H atoms are represented as small circles of arbitrary radius. The hydrogen bond is represented as dashed line.

Figure 2
View showing the disorder in molecule B. Bonds in the minor disorder component are shown as dashed lines. Table 1 Hydrogen-bond geometry (Å , ).  , contains a cyclohexyl ring substituted by a CH 2 group but, to the best of our knowledge, there are no reported structures that have a cyclohexyl group substituted by a hydroxyl at C9A (C9B).

Synthesis and crystallization
To a 100 mL flask was added (1 g, 3.29 mmol) of (1S,3R,8S,9R,10S)-2,2-dichloro-3,7,7,10-tetramethyl-9,10-epoxytricyclo[6.4.0.0 1,3 ]dodecane in 25 mL of dichloromethane. The mixture was cooled to 273.15 K in an ice bath prior to dropwise addition of 8 mL of concentrated hydrobromic acid. The mixture was stirred for 30 min. TLC control showed that the reaction was complete. The reaction mixture was extracted with dichloromethane (3 Â 30mL) and the organic layer was washed first with water and then with a saturated solution of NaHCO 3 , dried over anhydrous Na 2 SO 4 and concentrated under reduced pressure. The crude product was purified by chromatography on silica gel (230-400 mesh) with hexane/ ethyl acetate (97:3) as eluent to give the title compound in 64% yield. X-ray quality crystals were obtained by slow evaporation from a petroleum ether solution.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. All H atoms were initially located in a difference Fourier map but they were placed in geometrically idealized positions and constrained to ride on their parent atoms with C-H distances = 1.0 Å (Cmethine), 0.98 Å (Cmethyl), 0.99 Å (Cmethylene) and 0.84 Å (hydroxyl), with U iso (H) = 1.2U eq (C methine , C methylene ) or 1.5U eq (C methyl , O hydroxyl ).

Special details
Experimental. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm, CrysAlisPro (Agilent Technologies, 2014) 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.