2-Bromo-1,6,6-trimethyl-6,7,8,9-tetrahydrophenanthro[1,2-b]furan-10,11-dione

In the title compound, C19H17BrO3, the ring skeleton is located on a crystallographic mirror plane; two C atoms of the cyclohexene ring are disordered over the two locations to satisfy the preferred ring conformation. In the crystal, C—H⋯O hydrogen bonds link the molecules into chains along the a axis. π–π stacking interactions between benzoquinone rings, with a centroid–centroid distance of 3.7225 (4) Å, are also observed, which connect the chains into a two-dimensional networkparallel to the ab plane.

In the title compound, C 19 H 17 BrO 3 , the ring skeleton is located on a crystallographic mirror plane; two C atoms of the cyclohexene ring are disordered over the two locations to satisfy the preferred ring conformation. In the crystal, C-HÁ Á ÁO hydrogen bonds link the molecules into chains along the a axis.stacking interactions between benzoquinone rings, with a centroid-centroid distance of 3.7225 (4) Å , are also observed, which connect the chains into a two-dimensional networkparallel to the ab plane.

Comment
The Chinese herbal medicine, danshen, comes from the dried root of Salvia miltiorrhiza Bunge and Salvia przewalskii Maxim(Labiatae). Tanshinone IIA is the major active component isolated from danshen, which has unique curative effect in treating coronary heart disease (Chang et al., 1991;Wang et al., 2005), antitumour (Ryu et al., 1997), myocardial infarction and angina pectoris (Xue et al., 1999). The title compound, C 19 H 17 BrO 3 , is derivative obtained by modification of Tanshinone IIA and may be used for obtaining molecules with higher bioactivity and better solubility.

Experimental
Tanshinone IIA (0.3 mmol) was added to dry dichloromethane(15 mL)in a three neck flask. The mixture was stirred and was heated to reflux temperature. And then, N-bromosuccinimide(0.36mmol) and benzoyl peroxide(0.03mmol) were dropped into the flask. After reflux reaction for 9h and left stirring about 17h at room temperature, the solvent in flask was evaporated. The residue was purified by column chromatography on silica gel with ethyl acetate/petroleum ether to afford the title compound solid (109 mg, yield 97.08%). The crimson crystals of the title compound for structure determination were obtained from recrystallization of the product from ethyl acetate at room temperature.

Refinement
H1W and H2W were located by a difference map and refined isotropically. All of the remaining H atoms were positioned geometrically and treated as riding, with C-H bonding lengths constrained to 0.93 Å (aromatic CH) or 0.97 Å (methylene CH 2 ), and with U iso (H) = 1.2U eq (C) or 1.5U eq (methylene C).The carbon atoms of C15 and C16 located from the terminal cyclohexene ring and five hydrogen atoms H13a, H13b, H13c, H14a, H14b were observed disordered at two close positions with the half occupancy, respectively.

Figure 1
The molecular structure of (I), with atom labels and 50% probability displacement ellipsoids for non-H atoms. C15, C16 atoms are in disorder over two locations but one for each atom is shown. Symmetry code used for (C18a): x,-y+3/2,z. Bromo-1,6,6-trimethyl-6,7,8,9-tetrahydrophenanthro[1,2- where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.22 e Å −3 Δρ min = −0.41 e Å −3 Special details 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 Rfactors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (