Received 8 November 2011
aDepartment of Chemistry, University of Wisconsin-Madison, 1101 University Ave, Madison, WI 53706, USA, and bDepartment of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706, USA
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The title compound, C28H30N2, is a symmetrical 2:2 product from the condensation of indole and cyclohexanone. It is the only reported 5,11-dihydroindolo[3,2-b]carbazole compound in which the spiro atoms are quaternary C atoms. Crystals were grown by vapor diffusion in a three-zone electric furnace. The molecule resides on a crystallographic inversion center. The cyclohexyl rings are in a slightly distorted chair conformation, whereas the indole units and the spiro-carbons are coplanar within 0.014 Å.
For condensations of indole with cyclohexanone that yield 1:1 or 1:2 products, see: Yadav et al. (2001). For indole-ketone condensation by forming vinylindole followed by a Diels-Alder reaction, see: Noland et al. (1993). Recrystallization by the vapor-phase diffusion approach is explained in Kloc et al. (1997). For information on the related compound trans-6,12-diphenyl-5,6,11,12-tetrahydroindolo[3,2-b]carbazole dimethyl sulfoxide tetrahydrofuran solvate, see: Gu et al. (2009). Related compounds were found in the Cambridge Structural Database (Allen, 2002). Geometrical parameters were analyzed using Mogul (Bruno et al., 2002).
Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT-Plus (Bruker, 2007); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL, FCF_filter (Guzei, 2007) and INSerter (Guzei, 2007); molecular graphics: SHELXTL and DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXTL, publCIF (Westrip, 2010) and modiCIFer (Guzei, 2007).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: NK2127 ).
EC thanks Professor Wayland E. Noland for his assistance in initiating this project.
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