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The title compound, C18H18N2, was synthesized by the dimerization of N-methyl­indole in the presence of iodine as a catalyst. In the crystal structure, the dihedral angle between the indole and indoline ring systems is 86.30 (3)°.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807028243/ez2083sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536807028243/ez2083Isup2.hkl
Contains datablock I

CCDC reference: 654971

Key indicators

  • Single-crystal X-ray study
  • T = 298 K
  • Mean [sigma](C-C) = 0.003 Å
  • R factor = 0.063
  • wR factor = 0.215
  • Data-to-parameter ratio = 18.0

checkCIF/PLATON results

No syntax errors found



Alert level B PLAT230_ALERT_2_B Hirshfeld Test Diff for C12 - C17 .. 9.14 su
Alert level C DIFMX01_ALERT_2_C The maximum difference density is > 0.1*ZMAX*0.75 _refine_diff_density_max given = 0.580 Test value = 0.525 DIFMX02_ALERT_1_C The maximum difference density is > 0.1*ZMAX*0.75 The relevant atom site should be identified. PLAT066_ALERT_1_C Predicted and Reported Transmissions Identical . ? PLAT097_ALERT_2_C Maximum (Positive) Residual Density ............ 0.58 e/A    PLAT154_ALERT_1_C The su's on the Cell Angles are Equal (x 10000) 3000 Deg. PLAT230_ALERT_2_C Hirshfeld Test Diff for C10 - C11 .. 5.33 su PLAT230_ALERT_2_C Hirshfeld Test Diff for C14 - C15 .. 5.07 su PLAT241_ALERT_2_C Check High Ueq as Compared to Neighbors for C11 PLAT790_ALERT_4_C Centre of Gravity not Within Unit Cell: Resd. # 1 C18 H18 N2
Alert level G PLAT793_ALERT_1_G Check the Absolute Configuration of C10 = ... R
0 ALERT level A = In general: serious problem 1 ALERT level B = Potentially serious problem 9 ALERT level C = Check and explain 1 ALERT level G = General alerts; check 4 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 6 ALERT type 2 Indicator that the structure model may be wrong or deficient 0 ALERT type 3 Indicator that the structure quality may be low 1 ALERT type 4 Improvement, methodology, query or suggestion 0 ALERT type 5 Informative message, check

Comment top

Indole has potentially reactive sites for a variety of chemical reactions to generate molecular diversity (Farhanullah et al., 2004). Indole derivatives, either natural or synthetic products, have been widely studied because of their therapeutic importance (Sundberg, 1996). Indoles are known to dimerize and trimerize in acidic media (Noland et al., 1960), and the derivatives of the indole dimer, i.e. a series of 1-imidoyl-2-(2- and 3-indolyl)indolines, are found to present potential diuretic activity (Wu et al., 1972). The title compound (I) was synthesized by dimerization of N-methylindole in the presence of iodine as a catalyst. Herein we report the crystal structure of (I).

The molecular structure of (I) is shown in Fig.1. A l l bond distances and angles are normal. The length of the bond linking the indole and the indoline rings (C2—C10) is 1.486 (3) Å. The indoline ring adopts an envelope conformation with atom C10 deviating from the N2/C11/C12/C17 plane by 0.501 (3) Å. The indole ring and the indoline ring are approximately perpendicular, and the dihedral angle between them is 86.30 (3)°.

Related literature top

For related literature on indole derivatives, see: Farhanullah et al. (2004); Noland & Hammer (1960); Sundberg (1996); Wu et al. (1972).

Experimental top

A mixture of N-methylindole (10 mmol) and I2 (1 mmol) was stirred in acetonitrile (30 ml) at room temperature for a few s. After completion of the reaction (TLC, < 1 min), the mixture was treated with aqueous Na2S2O3 solution (5%, 30 ml). The product was extracted with ethyl acetate (3 × 30 ml). The combined organic layer was dried with anhydrous sodium sulfate, and purified by column chromatography (ethyl acetate:petroleum ether = 1:20) to afford the title compound (85% yield). Recrystallization by slow evaporation of a methanol solution was carried out to obtain good, diffraction quality crystals.

Refinement top

All H atoms were positioned geometrically and allowed to ride on their respective parent atoms, with C—H = 0.93, 0.96, 0.97 or 0.98 Å and Uiso(H) = 1.2 or 1.5 Ueq(C).

Structure description top

Indole has potentially reactive sites for a variety of chemical reactions to generate molecular diversity (Farhanullah et al., 2004). Indole derivatives, either natural or synthetic products, have been widely studied because of their therapeutic importance (Sundberg, 1996). Indoles are known to dimerize and trimerize in acidic media (Noland et al., 1960), and the derivatives of the indole dimer, i.e. a series of 1-imidoyl-2-(2- and 3-indolyl)indolines, are found to present potential diuretic activity (Wu et al., 1972). The title compound (I) was synthesized by dimerization of N-methylindole in the presence of iodine as a catalyst. Herein we report the crystal structure of (I).

The molecular structure of (I) is shown in Fig.1. A l l bond distances and angles are normal. The length of the bond linking the indole and the indoline rings (C2—C10) is 1.486 (3) Å. The indoline ring adopts an envelope conformation with atom C10 deviating from the N2/C11/C12/C17 plane by 0.501 (3) Å. The indole ring and the indoline ring are approximately perpendicular, and the dihedral angle between them is 86.30 (3)°.

For related literature on indole derivatives, see: Farhanullah et al. (2004); Noland & Hammer (1960); Sundberg (1996); Wu et al. (1972).

Computing details top

Data collection: SMART (Bruker, 2003); cell refinement: SAINT (Bruker, 2003); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997a); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997a); molecular graphics: SHELXTL (Sheldrick, 1997b); software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. A perspective view of (I) with atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii.
1-Methyl-3-(1-methyl-2,3-dihydro-1H-indol-2-yl)-1H-indole top
Crystal data top
C18H18N2Z = 2
Mr = 262.34F(000) = 280
Triclinic, P1Dx = 1.212 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 7.3843 (15) ÅCell parameters from 3267 reflections
b = 10.282 (2) Åθ = 3.1–27.5°
c = 10.757 (2) ŵ = 0.07 mm1
α = 65.54 (3)°T = 298 K
β = 75.14 (3)°Block, colorless
γ = 84.22 (3)°0.51 × 0.49 × 0.23 mm
V = 718.6 (3) Å3
Data collection top
Bruker SMART CCD APEXII
diffractometer
3267 independent reflections
Radiation source: fine-focus sealed tube2203 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.017
Detector resolution: 8.40 pixels mm-1θmax = 27.5°, θmin = 3.1°
ω scansh = 99
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
k = 1313
Tmin = 0.964, Tmax = 0.984l = 1313
7121 measured reflections
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)] = 0.063Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.215H-atom parameters constrained
S = 1.09 w = 1/[σ2(Fo2) + (0.1209P)2 + 0.0915P]
where P = (Fo2 + 2Fc2)/3
3267 reflections(Δ/σ)max < 0.001
181 parametersΔρmax = 0.58 e Å3
0 restraintsΔρmin = 0.29 e Å3
Crystal data top
C18H18N2γ = 84.22 (3)°
Mr = 262.34V = 718.6 (3) Å3
Triclinic, P1Z = 2
a = 7.3843 (15) ÅMo Kα radiation
b = 10.282 (2) ŵ = 0.07 mm1
c = 10.757 (2) ÅT = 298 K
α = 65.54 (3)°0.51 × 0.49 × 0.23 mm
β = 75.14 (3)°
Data collection top
Bruker SMART CCD APEXII
diffractometer
3267 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
2203 reflections with I > 2σ(I)
Tmin = 0.964, Tmax = 0.984Rint = 0.017
7121 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0630 restraints
wR(F2) = 0.215H-atom parameters constrained
S = 1.09Δρmax = 0.58 e Å3
3267 reflectionsΔρmin = 0.29 e Å3
181 parameters
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
N10.0594 (2)0.54541 (17)0.62999 (18)0.0532 (5)
N20.2976 (3)0.2855 (2)1.07571 (19)0.0608 (5)
C10.1060 (3)0.5440 (2)0.7237 (2)0.0528 (5)
H1A0.17620.62480.72200.063*
C20.1544 (3)0.4082 (2)0.8201 (2)0.0478 (5)
C30.0081 (3)0.3184 (2)0.78479 (19)0.0441 (5)
C40.0237 (3)0.1719 (2)0.8403 (2)0.0527 (5)
H4A0.06070.11080.91860.063*
C50.1830 (3)0.1188 (2)0.7771 (3)0.0644 (6)
H5A0.20530.02100.81350.077*
C60.3100 (3)0.2088 (3)0.6604 (3)0.0678 (7)
H6A0.41670.17000.62090.081*
C70.2826 (3)0.3533 (3)0.6016 (2)0.0586 (6)
H7A0.36710.41290.52210.070*
C80.1232 (3)0.4075 (2)0.66545 (19)0.0457 (5)
C90.1532 (4)0.6710 (2)0.5147 (2)0.0681 (7)
H9A0.08010.75420.51280.102*
H9B0.16710.66160.42760.102*
H9C0.27460.68050.52730.102*
C100.3284 (3)0.3675 (2)0.9342 (2)0.0514 (5)
H10A0.39350.45570.93340.062*
C110.4692 (4)0.2706 (3)0.9273 (3)0.0717 (7)
H11A0.55340.32620.86880.086*
H11B0.40530.20110.89210.086*
C120.5719 (3)0.1998 (2)1.0790 (2)0.0596 (6)
C130.7391 (4)0.1275 (3)1.1416 (3)0.0749 (7)
H13A0.81230.11841.08700.090*
C140.7986 (4)0.0678 (3)1.2871 (3)0.0731 (7)
H14A0.91100.01721.33010.088*
C150.6936 (3)0.0830 (2)1.3672 (3)0.0687 (7)
H15A0.73640.04351.46450.082*
C160.5242 (3)0.1559 (2)1.3072 (2)0.0622 (6)
H16A0.45310.16651.36240.075*
C170.4639 (3)0.2130 (2)1.1609 (2)0.0554 (6)
C180.1963 (4)0.3514 (3)1.1257 (3)0.0840 (8)
H18A0.18440.28711.21800.126*
H18B0.26030.43601.12980.126*
H18C0.07400.37671.06380.126*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0550 (10)0.0429 (9)0.0495 (9)0.0051 (7)0.0071 (8)0.0087 (7)
N20.0512 (10)0.0688 (12)0.0529 (10)0.0022 (9)0.0069 (8)0.0189 (9)
C10.0551 (12)0.0434 (10)0.0558 (11)0.0070 (9)0.0126 (9)0.0178 (9)
C20.0487 (11)0.0434 (10)0.0451 (10)0.0047 (8)0.0064 (8)0.0156 (8)
C30.0453 (10)0.0429 (10)0.0402 (9)0.0012 (8)0.0059 (8)0.0156 (8)
C40.0558 (12)0.0440 (10)0.0503 (11)0.0023 (9)0.0062 (9)0.0155 (9)
C50.0671 (14)0.0476 (12)0.0725 (15)0.0120 (10)0.0087 (12)0.0255 (11)
C60.0541 (13)0.0698 (15)0.0773 (15)0.0100 (11)0.0001 (11)0.0388 (13)
C70.0468 (11)0.0680 (14)0.0539 (12)0.0071 (10)0.0031 (9)0.0247 (10)
C80.0456 (10)0.0462 (10)0.0426 (9)0.0014 (8)0.0082 (8)0.0163 (8)
C90.0785 (16)0.0528 (13)0.0565 (13)0.0198 (11)0.0123 (12)0.0036 (10)
C100.0492 (11)0.0502 (11)0.0475 (10)0.0091 (9)0.0044 (9)0.0187 (9)
C110.0630 (14)0.0657 (15)0.0731 (15)0.0067 (12)0.0096 (12)0.0286 (12)
C120.0640 (13)0.0521 (12)0.0594 (12)0.0009 (10)0.0056 (11)0.0247 (10)
C130.0754 (16)0.0698 (16)0.0752 (16)0.0182 (13)0.0058 (14)0.0278 (13)
C140.0671 (15)0.0553 (13)0.0749 (16)0.0123 (11)0.0024 (13)0.0132 (12)
C150.0663 (15)0.0488 (12)0.0572 (13)0.0060 (11)0.0047 (11)0.0011 (10)
C160.0575 (13)0.0578 (12)0.0536 (12)0.0109 (10)0.0093 (10)0.0099 (10)
C170.0459 (11)0.0416 (10)0.0581 (12)0.0104 (8)0.0020 (9)0.0108 (9)
C180.0743 (17)0.102 (2)0.0733 (17)0.0125 (16)0.0119 (14)0.0337 (16)
Geometric parameters (Å, º) top
N1—C11.367 (3)C9—H9B0.9600
N1—C81.374 (3)C9—H9C0.9600
N1—C91.449 (3)C10—C111.546 (3)
N2—C181.384 (3)C10—H10A0.9800
N2—C171.395 (3)C11—C121.504 (3)
N2—C101.468 (3)C11—H11A0.9700
C1—C21.365 (3)C11—H11B0.9700
C1—H1A0.9300C12—C131.369 (3)
C2—C31.430 (3)C12—C171.383 (3)
C2—C101.486 (3)C13—C141.388 (4)
C3—C41.391 (3)C13—H13A0.9300
C3—C81.412 (3)C14—C151.359 (4)
C4—C51.383 (3)C14—H14A0.9300
C4—H4A0.9300C15—C161.385 (3)
C5—C61.386 (3)C15—H15A0.9300
C5—H5A0.9300C16—C171.396 (3)
C6—C71.370 (3)C16—H16A0.9300
C6—H6A0.9300C18—H18A0.9600
C7—C81.392 (3)C18—H18B0.9600
C7—H7A0.9300C18—H18C0.9600
C9—H9A0.9600
C1—N1—C8108.25 (16)N2—C10—C2114.55 (17)
C1—N1—C9125.9 (2)N2—C10—C11101.59 (18)
C8—N1—C9125.8 (2)C2—C10—C11116.85 (18)
C18—N2—C17120.3 (2)N2—C10—H10A107.8
C18—N2—C10117.3 (2)C2—C10—H10A107.8
C17—N2—C10107.50 (18)C11—C10—H10A107.8
C2—C1—N1111.00 (19)C12—C11—C10101.8 (2)
C2—C1—H1A124.5C12—C11—H11A111.4
N1—C1—H1A124.5C10—C11—H11A111.4
C1—C2—C3105.94 (17)C12—C11—H11B111.4
C1—C2—C10125.18 (19)C10—C11—H11B111.4
C3—C2—C10128.86 (18)H11A—C11—H11B109.3
C4—C3—C8118.78 (18)C13—C12—C17119.9 (2)
C4—C3—C2134.08 (18)C13—C12—C11131.8 (3)
C8—C3—C2107.13 (17)C17—C12—C11108.3 (2)
C5—C4—C3118.9 (2)C12—C13—C14119.6 (3)
C5—C4—H4A120.5C12—C13—H13A120.2
C3—C4—H4A120.5C14—C13—H13A120.2
C4—C5—C6121.1 (2)C15—C14—C13120.4 (2)
C4—C5—H5A119.4C15—C14—H14A119.8
C6—C5—H5A119.4C13—C14—H14A119.8
C7—C6—C5121.7 (2)C14—C15—C16121.5 (2)
C7—C6—H6A119.1C14—C15—H15A119.2
C5—C6—H6A119.1C16—C15—H15A119.2
C6—C7—C8117.4 (2)C15—C16—C17117.6 (2)
C6—C7—H7A121.3C15—C16—H16A121.2
C8—C7—H7A121.3C17—C16—H16A121.2
N1—C8—C7130.23 (19)C12—C17—N2110.0 (2)
N1—C8—C3107.68 (17)C12—C17—C16121.0 (2)
C7—C8—C3122.08 (19)N2—C17—C16128.9 (2)
N1—C9—H9A109.5N2—C18—H18A109.5
N1—C9—H9B109.5N2—C18—H18B109.5
H9A—C9—H9B109.5H18A—C18—H18B109.5
N1—C9—H9C109.5N2—C18—H18C109.5
H9A—C9—H9C109.5H18A—C18—H18C109.5
H9B—C9—H9C109.5H18B—C18—H18C109.5
C8—N1—C1—C20.5 (2)C18—N2—C10—C11171.3 (2)
C9—N1—C1—C2179.3 (2)C17—N2—C10—C1132.1 (2)
N1—C1—C2—C30.5 (2)C1—C2—C10—N2125.8 (2)
N1—C1—C2—C10178.07 (19)C3—C2—C10—N256.0 (3)
C1—C2—C3—C4179.1 (2)C1—C2—C10—C11115.6 (3)
C10—C2—C3—C40.6 (4)C3—C2—C10—C1162.6 (3)
C1—C2—C3—C80.3 (2)N2—C10—C11—C1230.0 (2)
C10—C2—C3—C8178.2 (2)C2—C10—C11—C12155.37 (19)
C8—C3—C4—C50.2 (3)C10—C11—C12—C13163.0 (3)
C2—C3—C4—C5178.9 (2)C10—C11—C12—C1718.9 (2)
C3—C4—C5—C60.0 (4)C17—C12—C13—C140.1 (4)
C4—C5—C6—C70.8 (4)C11—C12—C13—C14177.8 (2)
C5—C6—C7—C81.3 (4)C12—C13—C14—C151.2 (4)
C1—N1—C8—C7178.9 (2)C13—C14—C15—C160.9 (4)
C9—N1—C8—C72.2 (4)C14—C15—C16—C170.4 (3)
C1—N1—C8—C30.2 (2)C13—C12—C17—N2177.8 (2)
C9—N1—C8—C3179.1 (2)C11—C12—C17—N20.6 (2)
C6—C7—C8—N1179.5 (2)C13—C12—C17—C161.3 (3)
C6—C7—C8—C31.0 (3)C11—C12—C17—C16179.6 (2)
C4—C3—C8—N1179.05 (18)C18—N2—C17—C12159.2 (2)
C2—C3—C8—N10.0 (2)C10—N2—C17—C1221.5 (2)
C4—C3—C8—C70.3 (3)C18—N2—C17—C1621.8 (3)
C2—C3—C8—C7178.73 (19)C10—N2—C17—C16159.6 (2)
C18—N2—C10—C261.8 (3)C15—C16—C17—C121.5 (3)
C17—N2—C10—C2158.96 (18)C15—C16—C17—N2177.4 (2)

Experimental details

Crystal data
Chemical formulaC18H18N2
Mr262.34
Crystal system, space groupTriclinic, P1
Temperature (K)298
a, b, c (Å)7.3843 (15), 10.282 (2), 10.757 (2)
α, β, γ (°)65.54 (3), 75.14 (3), 84.22 (3)
V3)718.6 (3)
Z2
Radiation typeMo Kα
µ (mm1)0.07
Crystal size (mm)0.51 × 0.49 × 0.23
Data collection
DiffractometerBruker SMART CCD APEXII
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.964, 0.984
No. of measured, independent and
observed [I > 2σ(I)] reflections
7121, 3267, 2203
Rint0.017
(sin θ/λ)max1)0.650
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.063, 0.215, 1.09
No. of reflections3267
No. of parameters181
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.58, 0.29

Computer programs: SMART (Bruker, 2003), SAINT (Bruker, 2003), SAINT, SHELXS97 (Sheldrick, 1997a), SHELXL97 (Sheldrick, 1997a), SHELXTL (Sheldrick, 1997b), SHELXTL.

 

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