3,3-Dimethyl-1,2,3,4-tetrahydrocyclopenta[b]indole-1,2-dione (bruceolline E)

The title compound, C13H11NO2, crystallizes with two molecules in the asymmetric unit. The crystal packing is stabilized by N—H⋯O hydrogen bonds, which link the molecules into chains along [10], and weak C—H⋯O interactions.

The title compound, C 13 H 11 NO 2 , crystallizes with two molecules in the asymmetric unit. The crystal packing is stabilized by N-HÁ Á ÁO hydrogen bonds, which link the molecules into chains along [101], and weak C-HÁ Á ÁO interactions.

Experimental
JCB wishes to thank the School of Graduate Studies and Research, UWI, and the Government of Barbados for the funding of this research. JPJ acknowledges the NSF-MRI program (grant No. CHE1039027) for funds to purchase the X-ray diffractometer. tionality using selenium dioxide (Gribble et al., 1988) in 60% yield. Similar Nazarov cyclizations with indoles (Bergman & Venemalm, 1992;Cheng & Cheung, 1996;Ishikura et al., 2000;Miki et al., 2001;Churruca et al., 2010) have been reported.
We now report herein the first crystal structure of the title compound, C 13 H 11 NO 2 , bruceolline E, which confirms the cyclopenta[b] indole moiety and the α-diketone functionalities earlier assigned by NMR methods.
In the crystal structure of the title compound, C 13 H 11 NO 2 , two molecules crystallize in the asymmetric unit ( Fig. 1).

Refinement
H1NA and H1NB were located by a Fourier map and refined isotropically. All of the remaining H atoms were placed in their calculated positions and then refined using the riding model with Atom-H lengths of 0.95Å (CH) or 0.98Å (CH 3 ). Isotropic displacement parameters for these atoms were set to 1.19-1.20 (CH) or 1.4-1,50 (CH 3 ) times U eq of the parent atom. Fig. 1. Molecular structure of the title compound with two molecules in the asymmetric unit showing the atom labeling scheme and 50% probability displacement ellipsoids. Hall symbol: -P 1 Mo Kα radiation, λ = 0.71073 Å a = 9.1091 (7) Å Cell parameters from 5810 reflections b = 11.5337 (8) Å θ = 3.3-32.3°c = 11.8745 (9) Å µ = 0.09 mm −1 α = 63.230 (7)°T = 170 K β = 80.596 (6) 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.

sup-2 Figures
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 Rfactors(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.