supplementary materials


nk2127 scheme

Acta Cryst. (2012). E68, o1-o2    [ doi:10.1107/S1600536811051208 ]

5',11'-Dihydrodispiro[cyclohexane-1,6'-indolo[3,2-b]carbazole-12',1''-cyclohexane]

I. A. Guzei, L. C. Spencer, E. Codner and J. M. Boehm

Abstract top

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.

Comment top

Condensations of indole with cyclohexanone yield a variety of products, often 1:1 or 1:2 structures in which the carbonyl carbon is attached to the 3-position of one or more indole moieties (Yadav et al., 2001). These products are often useful as pharmaceutical intermediates, and a variety of catalysts and reaction conditions have been explored. A particularly interesting example of indole-ketone condensation chemistry is vinylindole formation followed by the Diels-Alder reaction (Noland et al., 1993). While investigating this reaction we isolated highly symmetrical 2:2 condensation products from preparations containing indole and a cyclic ketone (cyclohexanone, tert-butyl cyclohexanone, or cyclopentanone) using hydrochloric acid as a catalyst. These 2:2 condensation products possess unusual physical properties for this class of compound, including limited solubility in most solvents, decomposition without melting at temperatures over 300 °C, and fluorescence despite the absence of extended intramolecular conjugation. Due to the lack of a suitable recrystallization solvent we employed the vapor-phase diffusion approach of Kloc et al. (1997) to produce crystals of dispiro[cyclohexane-1,6'(1'H)-indolo[3,2-b]carbazole-12'(1H),1''-cyclohexane] (I).

Data mining of the Cambridge Structural Database (CSD; November 2011 update; Allen, 2002) revealed that (I) is the only crystallographically characterized condensation product of indole and cyclohexanone in which the spiro atoms are quaternary carbon atoms.

The molecule of (I) resides on a crystallographic inversion center. The amino hydrogen atoms do not participate in hydrogen bonding interactions due to the lack of acceptors. In contrast, the related compound trans-6,12-diphenyl-5,6,11,12-tetrahydroindolo[3,2-b]carbazole dimethyl sulfoxide tetrahydrofuran solvate (II) which also has hydrogen atoms on nitrogen atoms forms hydrogen bonding interactions with the oxygen atoms of the dimethyl sulfoxide solvent molecules (Gu et al., 2009).

A Mogul (Bruno et al., 2002) structural check confirmed that the geometrical parameters of (I) are typical except for the C10—C9—C14 angle. The latter measures 111.20 (10)° and is more obtuse than the average angle of 108.3 (9)° computed for related compounds. The difference is statistically significant. The two cyclohexyl substituents most closely resemble a chair conformation. The 5,11-dihydroindolo[3,2-b]carbazole core is planar within 0.0142 Å.

Related literature top

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).

Experimental top

Indole (3 g) was dissolved in 25 ml of cyclohexanone. Approximately 0.25 ml of concentrated HCl was added and the mixture was stirred at room temperature for 7–14 days. The resulting pink-white precipitate was isolated using vacuum filtration and washed in refluxing acetonitrile for 60 min.

In an alternative preparation, indole (3 g) and cyclohexanone (2.5 g) were dissolved in 25 ml of acetonitrile. Approximately 0.1 ml of concentrated HCl was added and the mixture was heated to reflux for 24 h. The product was recovered from an accompanying intractable tarry material by washing with acetone followed by reflux in fresh acetonitrile.

Crystals were grown in a three-zone electric furnace. A 1 g sample of the material was placed on a microscope cover slip and inserted into a 25 mm quartz tube. The tube was placed in the furnace and connected to a supply of argon. The argon flow was adjusted to 2 ml/min, the tube was purged of air and heated in three zones. The first zone contained the initial sample and was heated to 308–310 °C to promote volatilization. The second zone was the region of molecular transport and was heated to 280–290 °C. The third zone was heated to 200 °C to encourage crystal deposition. These heating and gas flow conditions yielded needle-shaped crystals approximately 500 µm in the short dimensions and 10–15 mm long over 14 h.

Refinement top

All H-atoms attached to carbon atoms were placed in idealized locations and refined as riding with appropriate thermal displacement coefficients Uĩso(H) = 1.2 times Ueq(bearing atom). Default effective X—H distances for T = -173.0°C C(sp3)–2H=0.99, C(sp2)–H=0.95. The hydrogen atom attached to N1 was located in the difference map and refined independently.

Computing details top

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT-Plus (Bruker, 2007); data reduction: SAINT-Plus (Bruker, 2007); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008), FCF_filter (Guzei, 2007) and INSerter (Guzei, 2007); molecular graphics: SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXTL (Sheldrick, 2008), publCIF (Westrip, 2010) and modiCIFer (Guzei, 2007).

Figures top
[Figure 1] Fig. 1. Molecular structure of (I) (Brandenburg, 1999). Displacement ellipsoids are shown at the 50% probability level and C-bound H atoms are omitted. The compound resides on a crystallographic inversion center. Symmetry transformations used to generate equivalent atoms: (i) -x + 1,-y,-z.
5',11'-Dihydrodispiro[cyclohexane-1,6'-indolo[3,2-b]carbazole- 12',1''-cyclohexane] top
Crystal data top
C28H30N2F(000) = 424
Mr = 394.54Dx = 1.291 Mg m3
Monoclinic, P21/cCu Kα radiation, λ = 1.54178 Å
Hall symbol: -P 2ybcCell parameters from 9920 reflections
a = 7.4655 (2) Åθ = 5.5–67.3°
b = 13.6820 (4) ŵ = 0.57 mm1
c = 10.5348 (3) ÅT = 100 K
β = 109.380 (1)°Block, colourless
V = 1015.08 (5) Å30.38 × 0.30 × 0.19 mm
Z = 2
Data collection top
Bruker SMART APEXII area-detector
diffractometer
1826 independent reflections
Radiation source: fine-focus sealed tube1779 reflections with I > 2σ(I)
graphiteRint = 0.022
0.50° ω and 0.5 ° φ scansθmax = 67.7°, θmin = 5.5°
Absorption correction: analytical
(SADABS; Bruker, 2007)
h = 88
Tmin = 0.813, Tmax = 0.900k = 1616
20619 measured reflectionsl = 1212
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.041Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.113H atoms treated by a mixture of independent and constrained refinement
S = 0.99 w = 1/[σ2(Fo2) + (0.0708P)2 + 0.5526P]
where P = (Fo2 + 2Fc2)/3
1826 reflections(Δ/σ)max < 0.001
140 parametersΔρmax = 0.35 e Å3
0 restraintsΔρmin = 0.22 e Å3
Crystal data top
C28H30N2V = 1015.08 (5) Å3
Mr = 394.54Z = 2
Monoclinic, P21/cCu Kα radiation
a = 7.4655 (2) ŵ = 0.57 mm1
b = 13.6820 (4) ÅT = 100 K
c = 10.5348 (3) Å0.38 × 0.30 × 0.19 mm
β = 109.380 (1)°
Data collection top
Bruker SMART APEXII area-detector
diffractometer
1826 independent reflections
Absorption correction: analytical
(SADABS; Bruker, 2007)
1779 reflections with I > 2σ(I)
Tmin = 0.813, Tmax = 0.900Rint = 0.022
20619 measured reflectionsθmax = 67.7°
Refinement top
R[F2 > 2σ(F2)] = 0.041H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.113Δρmax = 0.35 e Å3
S = 0.99Δρmin = 0.22 e Å3
1826 reflectionsAbsolute structure: ?
140 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.79965 (15)0.12731 (8)0.03500 (11)0.0165 (3)
H10.837 (2)0.1597 (11)0.0234 (16)0.017 (4)*
C10.87673 (18)0.13818 (9)0.17213 (13)0.0164 (3)
C21.02992 (18)0.19577 (9)0.24794 (13)0.0182 (3)
H21.09950.23470.20590.022*
C31.07633 (18)0.19384 (9)0.38671 (13)0.0191 (3)
H31.17900.23240.44100.023*
C40.97353 (19)0.13558 (9)0.44782 (13)0.0190 (3)
H41.00830.13530.54310.023*
C50.82312 (18)0.07871 (9)0.37278 (13)0.0173 (3)
H50.75560.03940.41600.021*
C60.77079 (18)0.07954 (9)0.23203 (13)0.0157 (3)
C70.62336 (17)0.03331 (9)0.12319 (12)0.0154 (3)
C80.64558 (17)0.06437 (9)0.00578 (13)0.0151 (3)
C90.47366 (17)0.03714 (9)0.13577 (12)0.0153 (3)
C100.57699 (18)0.12878 (9)0.21510 (13)0.0170 (3)
H10A0.62100.16960.15370.020*
H10B0.69100.10650.28860.020*
C110.45854 (19)0.19262 (9)0.27583 (13)0.0189 (3)
H11A0.35710.22540.20270.023*
H11B0.54030.24380.33290.023*
C120.3696 (2)0.13171 (10)0.36026 (13)0.0217 (3)
H12A0.47090.10090.43540.026*
H12B0.29410.17460.39900.026*
C130.24144 (19)0.05256 (10)0.27410 (13)0.0194 (3)
H13A0.18550.01350.33060.023*
H13B0.13620.08370.20200.023*
C140.35216 (18)0.01490 (9)0.21105 (13)0.0172 (3)
H14A0.43750.05620.28310.021*
H14B0.26070.05890.14680.021*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0180 (6)0.0177 (6)0.0138 (6)0.0033 (4)0.0054 (4)0.0008 (4)
C10.0180 (6)0.0154 (6)0.0148 (6)0.0033 (5)0.0041 (5)0.0004 (5)
C20.0191 (7)0.0160 (6)0.0192 (7)0.0008 (5)0.0058 (5)0.0009 (5)
C30.0178 (6)0.0174 (6)0.0181 (7)0.0022 (5)0.0007 (5)0.0022 (5)
C40.0214 (7)0.0188 (7)0.0149 (6)0.0021 (5)0.0036 (5)0.0005 (5)
C50.0196 (6)0.0158 (6)0.0166 (6)0.0006 (5)0.0063 (5)0.0002 (5)
C60.0160 (6)0.0130 (6)0.0183 (6)0.0021 (5)0.0061 (5)0.0006 (5)
C70.0156 (6)0.0147 (6)0.0144 (6)0.0027 (5)0.0032 (5)0.0015 (5)
C80.0140 (6)0.0133 (6)0.0177 (6)0.0008 (4)0.0050 (5)0.0007 (5)
C90.0171 (6)0.0151 (6)0.0138 (6)0.0007 (5)0.0055 (5)0.0003 (5)
C100.0178 (6)0.0167 (7)0.0152 (6)0.0004 (5)0.0039 (5)0.0008 (5)
C110.0223 (7)0.0159 (6)0.0159 (6)0.0017 (5)0.0030 (5)0.0019 (5)
C120.0276 (7)0.0224 (7)0.0169 (6)0.0049 (5)0.0099 (6)0.0016 (5)
C130.0204 (7)0.0224 (7)0.0176 (6)0.0027 (5)0.0090 (5)0.0032 (5)
C140.0191 (6)0.0169 (6)0.0158 (6)0.0002 (5)0.0060 (5)0.0013 (5)
Geometric parameters (Å, °) top
N1—C11.3743 (16)C9—C8i1.5080 (17)
N1—C81.3872 (16)C9—C141.5608 (16)
N1—H10.876 (17)C9—C101.5612 (17)
C1—C21.4001 (18)C10—C111.5264 (17)
C1—C61.4137 (18)C10—H10A0.9900
C2—C31.3862 (19)C10—H10B0.9900
C2—H20.9500C11—C121.5227 (19)
C3—C41.4024 (19)C11—H11A0.9900
C3—H30.9500C11—H11B0.9900
C4—C51.3791 (18)C12—C131.5282 (19)
C4—H40.9500C12—H12A0.9900
C5—C61.4026 (18)C12—H12B0.9900
C5—H50.9500C13—C141.5299 (17)
C6—C71.4452 (17)C13—H13A0.9900
C7—C81.3690 (18)C13—H13B0.9900
C7—C91.5146 (17)C14—H14A0.9900
C8—C9i1.5080 (17)C14—H14B0.9900
C1—N1—C8109.12 (11)C14—C9—C10111.20 (10)
C1—N1—H1124.3 (10)C11—C10—C9115.59 (10)
C8—N1—H1126.3 (10)C11—C10—H10A108.4
N1—C1—C2129.67 (12)C9—C10—H10A108.4
N1—C1—C6107.86 (11)C11—C10—H10B108.4
C2—C1—C6122.47 (12)C9—C10—H10B108.4
C3—C2—C1117.50 (12)H10A—C10—H10B107.4
C3—C2—H2121.2C12—C11—C10110.94 (11)
C1—C2—H2121.2C12—C11—H11A109.5
C2—C3—C4120.77 (12)C10—C11—H11A109.5
C2—C3—H3119.6C12—C11—H11B109.5
C4—C3—H3119.6C10—C11—H11B109.5
C5—C4—C3121.54 (12)H11A—C11—H11B108.0
C5—C4—H4119.2C11—C12—C13110.44 (10)
C3—C4—H4119.2C11—C12—H12A109.6
C4—C5—C6119.31 (12)C13—C12—H12A109.6
C4—C5—H5120.3C11—C12—H12B109.6
C6—C5—H5120.3C13—C12—H12B109.6
C5—C6—C1118.40 (11)H12A—C12—H12B108.1
C5—C6—C7134.98 (12)C12—C13—C14111.31 (10)
C1—C6—C7106.61 (11)C12—C13—H13A109.4
C8—C7—C6106.99 (11)C14—C13—H13A109.4
C8—C7—C9126.21 (11)C12—C13—H13B109.4
C6—C7—C9126.79 (11)C14—C13—H13B109.4
C7—C8—N1109.41 (11)H13A—C13—H13B108.0
C7—C8—C9i127.44 (12)C13—C14—C9115.74 (10)
N1—C8—C9i123.14 (11)C13—C14—H14A108.3
C8i—C9—C7106.34 (10)C9—C14—H14A108.3
C8i—C9—C14111.30 (10)C13—C14—H14B108.3
C7—C9—C14108.92 (10)C9—C14—H14B108.3
C8i—C9—C10110.83 (10)H14A—C14—H14B107.4
C7—C9—C10108.06 (10)
C8—N1—C1—C2178.37 (13)C9—C7—C8—C9i0.9 (2)
C8—N1—C1—C60.86 (13)C1—N1—C8—C70.72 (14)
N1—C1—C2—C3179.13 (12)C1—N1—C8—C9i179.29 (11)
C6—C1—C2—C30.01 (19)C8—C7—C9—C8i0.78 (18)
C1—C2—C3—C40.44 (19)C6—C7—C9—C8i179.97 (11)
C2—C3—C4—C50.2 (2)C8—C7—C9—C14120.82 (13)
C3—C4—C5—C60.40 (19)C6—C7—C9—C1459.99 (15)
C4—C5—C6—C10.80 (18)C8—C7—C9—C10118.26 (13)
C4—C5—C6—C7178.16 (13)C6—C7—C9—C1060.93 (15)
N1—C1—C6—C5179.91 (11)C8i—C9—C10—C1182.20 (13)
C2—C1—C6—C50.61 (18)C7—C9—C10—C11161.65 (10)
N1—C1—C6—C70.68 (13)C14—C9—C10—C1142.16 (14)
C2—C1—C6—C7178.62 (11)C9—C10—C11—C1252.32 (14)
C5—C6—C7—C8179.29 (14)C10—C11—C12—C1359.53 (14)
C1—C6—C7—C80.25 (13)C11—C12—C13—C1458.68 (14)
C5—C6—C7—C91.4 (2)C12—C13—C14—C950.47 (14)
C1—C6—C7—C9179.57 (11)C8i—C9—C14—C1382.87 (13)
C6—C7—C8—N10.27 (14)C7—C9—C14—C13160.20 (10)
C9—C7—C8—N1179.06 (11)C10—C9—C14—C1341.22 (14)
C6—C7—C8—C9i179.73 (11)
Symmetry codes: (i) −x+1, −y, −z.
Table 1
Selected geometric parameters (Å, °)
top
N1—C11.3743 (16)N1—C81.3872 (16)
C1—N1—C8109.12 (11)
Acknowledgements top

EC thanks Professor Wayland E. Noland for his assistance in initiating this project.

references
References top

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