2-(1,2,3,4-Tetra­hydro­carbazol-2-yl)­butyl­amine

The title compound, C₁₆H₂₂N₂, consists of a carbazole skeleton with a butyl­amine side chain at position 2. Molecules are linked about inversion centres by N—H...N hydrogen bonds [N...N 2.950 (3) Å] to form centrosymmetric dimers.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.055
• wR factor = 0.157
• Data-to-parameter ratio = 14.8

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



PLAT_420  Alert C D-H Without Acceptor       N(2)   -   H(2B)             ?


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 1 Alert Level C = Please check

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S1. Comment

1,2,3,4-Tetrahydrocarbazole derivatives can be considered to be synthetic precursors of tetracyclic indole alkaloids. They have tricyclic ring systems with the rings named as A, B and C as in the strychnos type of indole alkaloids (Bosch & Bonjoch, 1988). The possibility of synthesizing the indole type of alkaloids by substitution at different positions is currently under investigation (Patır et al., 1997).

Tetrahydrocarbazole systems are present in the framework of a number of indole-type alkaloids of biological interest (Phillipson & Zenk, 1980; Saxton, 1983; Abraham, 1975).

The structures of tetrahydrocarbazole derivatives having different substituents at different positions of the carbazole core, e.g. 4-methylcarbazole-3-carboxylic acid, (II) (Hökelek et al., 2001), 1-benzyloxy-1,2,3,4-tetrahydrocarbazole, (III) (Hökelek et al., 2000), N-(1,2,3,4-tetrahydrocarbazole-1-yl)-2-methoxyacetamide, (IV) (Hökelek & Patır, 2000a), 2,3-dihydro-3-ethyl-9-(phenylsulfonyl)carbazol-4(1H)-one, (V) (Hökelek & Patır, 2000b), N-(2,2-dimethoxyethyl)-N-(9-methoxymethyl-1,2,3,4-tetrahydrospiro[carbazole- 1,2'-[1,3]dithiolan]-4-yl)benzamide, (VI) (Hökelek & Patır, 1999) and 1,2,3,4-tetrahydrocarbazole-1-spiro-2'-[1,3]dithiolane, (VII) (Hökelek et al., 1994) have been the subject of much interest in our laboratory.

The title compound, (I), may be an interesting intermediate in the synthesis of tetracyclic indole alkaloids (Magnus et al., 1992).

The present structure determination of (I) was undertaken in order to understand the effects of the butylamine side chain at position 2 on the geometry of the carbazole system, and to compare the obtained results with those of previously reported tetrahydrocarbazole derivatives.

Compound (I) (Fig. 1) contains a carbazole skeleton with a butylamine side chain bonded as substituent at position 2. As can be seen from the packing diagram (Fig. 2), there are intermolecular hydrogen bonding and intermolecular contact between the indole N—H group and side-chain NH₂ groups of the neighbouring molecules [N2ⁱ···H9(N9) 2.096 Å, N9—H9···N2ⁱ 172.1° and N9ⁱ···H2A 2.626 Å, N2—H2A···N9ⁱ 103.6°, respectively; symmetry code: (i) -x, -y, -z + 2]. These intermolecular hydrogen bonding and contact cause dimerization of the substituted carbazole molecules. Dipole–dipole and van der Waals interactions are also effective in the molecular packing. The substituent and the intermolecular interactions may cause increases in the exocyclic and endocyclic angles C4—C4A—C5A [130.8 (2)°], C5—C5A—C4A [135.1 (2)°], C2—C3—C4 [112.2 (2)°] and C1—C9A—C4A [126.4 (2)°].

The absence of any protecting group at atom N9 causes shortening of the C—N bonds [N9—C8A 1.373 (3) Å and N9—C9A 1.382 (3) Å]. They are shorter than the corresponding values [1.390 (10) and 1.404 (9) Å] in N-(2-methoxyethyl)-N-(2,3,4,9-tetrahydrospiro[1H-carbazole-1,2-(1,3)dithiolane]- 4-yl)benzenesulfonamide, (VIII) (Patır et al., 1997) and [1.423 (5) and 1.412 (5) Å] in 2,3-dihydro-9-(phenylsulfonyl)carbazole-4-(1H)-one, (IX) (Hökelek et al., 1994). On the other hand, N9—C8A is nearly the same, but N9—C9A is longer than the corresponding values [1.382 (2) and 1.355 (3) Å] in spiro[carbazole-1(2H),2'-[1,3]-dithiolan]-4(3H)-one, (X) (Hökelek et al., 1998), while N9—C8A is shorter and N9—C9A is nearly the same with respect to the corresponding ones [1.396 (2) and 1.377 (2) Å] in 9-acetonyl-3-ethylidene-1,2,3,4-tetrahydrospiro[carbazole-1,2'-[1,3]dithiolan]- 4-one, (XI) (Hökelek et al., 1999).

The butylamine side chain in (I) causes notable changes on the geometry of the carbazole core, compared with the reported values in compounds (VI), (VII), (IX), (X) and (XI) (Table 2).

In conclusion, the types of substituent groups, depending on their electron releasing/denoting properties, and their bonding positions have a significant effect on the geometry of the carbazole core.

An examination of the deviations from the least-squares planes through the individual rings shows that rings A (C5A/C5–C8/C8A) and B (C4A/C5A/C8A/N9/C9A) are nearly planar and ring C (C1—C4/C4A/C9A) is not planar, with a maximum deviation for the C3 [0.340 (3) Å] atom. These rings are also twisted with respect to each other. The dihedral angles between the best least-squares planes are A/B = 1.63 (8), A/C = 8.21 (7) and B/C = 6.84 (8)°. In ring C, the puckering parameters, i.e. the angles between the best planes C1/C3/C4/C9A, C4/C4a/C9A and C1/C2/C3, are 7.0 (2) and 50.6 (2)°, respectively. Ring C has a sofa conformation with a local pseudo-twofold axis running along the midpoints of the C2—C3 and C4a—C9A bonds.

S2. Experimental

2-(1,2,3,4-Tetrahydrocarbazole-2-yl)butyronitrile (5.0 g, 21.0 mmol) was added slowly to a suspension of lithium aluminium hydride (2.4 g, 62.0 mmol) in tetrahydrofuran (50 ml) at 273 K. The reaction mixture was refluxed for 5 h under a nitrogen atmosphere, then excess of lithium aluminium hydride was destroyed with methanol–water mixture (20:1) and extracted with ethyl acetate. The organic layer was dried with magnesium sulfate and the solvent was evaporated at reduced pressure. The residue was purified by column chromatography using silica gel, ethyl acetate–methanol (9:1) to afford 4.5 g (88%) of the product. The product was recrystallized from ethyl acetate–cyclohexane mixture (m.p. 425 K).

S3. Refinement

The positions of the H atoms were calculated geometrically at distances of 0.86 (NH and NH₂), 0.93 and 0.98 (CH), 0.96 (CH₃) and 0.97 (CH₂) from the corresponding atoms, and a riding model was used during the refinement process.

Computing details

Data collection: MolEN (Fair, 1990); cell refinement: MolEN; data reduction: MolEN; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: MolEN.

Figures

	Fig. 1. An ORTEPII (Johnson, 1976) drawing of the title molecule with the atom-numbering scheme. The displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. The packing diagram for (I). Hydrogen bonds are shown as dotted lines and H atoms not involved in hydrogen bonding have been omitted.

(I)

Crystal data

C16H22N2	Z = 2
Mr = 242.36	F(000) = 264
Triclinic, P1	Dx = 1.167 Mg m^−3
a = 7.9665 (10) Å	Cu Kα radiation, λ = 1.54180 Å
b = 8.911 (10) Å	Cell parameters from 25 reflections
c = 10.7318 (10) Å	θ = 21–43°
α = 69.59 (6)°	µ = 0.52 mm^−1
β = 75.783 (10)°	T = 296 K
γ = 80.87 (8)°	Rod, yellow
V = 689.9 (8) Å^3	0.30 × 0.25 × 0.20 mm

Data collection

Enraf-Nonius CAD-4 diffractometer	1637 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.015
Graphite monochromator	θmax = 74.2°, θmin = 5.7°
ω/2θ scans	h = 0→9
Absorption correction: ψ scan empirical (using intensity measurements) via ψ scans (Fair, 1990)	k = −10→11
Tmin = 0.855, Tmax = 0.901	l = −12→13
2927 measured reflections	3 standard reflections every 120 min
2807 independent reflections	intensity decay: 1%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.055	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.157	H atoms treated by a mixture of independent and constrained refinement
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0911P)^2] where P = (Fo^2 + 2Fc^2)/3
2406 reflections	(Δ/σ)max < 0.001
163 parameters	Δρmax = 0.27 e Å^−3
0 restraints	Δρmin = −0.21 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
C13	−0.1054 (3)	−0.0112 (3)	0.7310 (2)	0.0523 (5)
H13A	−0.1215	0.0784	0.7655	0.063*
H13B	−0.0907	0.0322	0.6329	0.063*
C11	0.1092 (3)	−0.2434 (3)	0.6975 (2)	0.0542 (6)
H11A	0.0043	−0.2817	0.6928	0.065*
H11B	0.1709	−0.1947	0.6052	0.065*
N2	−0.2607 (2)	−0.1008 (2)	0.7869 (2)	0.0568 (5)
H2A	−0.2524	−0.2009	0.8341	0.068*
H2B	−0.3602	−0.0533	0.7724	0.068*
C12	0.2219 (4)	−0.3857 (3)	0.7682 (3)	0.0721 (7)
H12A	0.2487	−0.4611	0.7190	0.108*
H12B	0.1608	−0.4367	0.8590	0.108*
H12C	0.3276	−0.3496	0.7713	0.108*
N9	0.3919 (2)	0.2037 (2)	0.91651 (18)	0.0515 (5)
H9	0.3446	0.1797	1.0014	0.062*
C9A	0.3388 (3)	0.1611 (2)	0.8210 (2)	0.0444 (5)
C10	0.0581 (3)	−0.1151 (2)	0.7672 (2)	0.0458 (5)
H10	0.0302	−0.1723	0.8651	0.055*
C8A	0.5338 (3)	0.2913 (2)	0.8517 (2)	0.0468 (5)
C5A	0.5682 (3)	0.3056 (2)	0.7128 (2)	0.0471 (5)
C4A	0.4414 (3)	0.2206 (2)	0.6967 (2)	0.0444 (5)
C3	0.2425 (3)	0.1181 (3)	0.6045 (2)	0.0498 (5)
H3A	0.1494	0.2030	0.6033	0.060*
H3B	0.2407	0.0745	0.5338	0.060*
C1	0.1930 (3)	0.0573 (3)	0.8559 (2)	0.0484 (5)
H1A	0.0827	0.1206	0.8656	0.058*
H1B	0.1968	−0.0280	0.9414	0.058*
C2	0.2101 (3)	−0.0148 (2)	0.7428 (2)	0.0451 (5)
H2	0.3151	−0.0890	0.7455	0.054*
C4	0.4174 (3)	0.1894 (3)	0.5742 (2)	0.0498 (5)
H4A	0.5113	0.1151	0.5488	0.060*
H4B	0.4205	0.2890	0.4987	0.060*
C5	0.7104 (3)	0.3901 (3)	0.6258 (3)	0.0558 (6)
H5	0.7362	0.4028	0.5336	0.067*
C8	0.6347 (3)	0.3563 (3)	0.9052 (3)	0.0574 (6)
H8	0.6090	0.3463	0.9969	0.069*
C6	0.8103 (3)	0.4533 (3)	0.6798 (3)	0.0655 (7)
H6	0.9044	0.5091	0.6227	0.079*
C7	0.7749 (3)	0.4365 (3)	0.8176 (3)	0.0685 (7)
H7	0.8463	0.4797	0.8510	0.082*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C13	0.0430 (11)	0.0560 (12)	0.0546 (13)	−0.0018 (9)	−0.0129 (10)	−0.0127 (10)
C11	0.0553 (13)	0.0535 (12)	0.0583 (14)	−0.0045 (10)	−0.0115 (11)	−0.0236 (10)
N2	0.0406 (10)	0.0665 (11)	0.0592 (12)	−0.0007 (8)	−0.0140 (8)	−0.0145 (9)
C12	0.0791 (18)	0.0563 (14)	0.0874 (19)	0.0098 (12)	−0.0256 (15)	−0.0321 (13)
N9	0.0532 (11)	0.0572 (10)	0.0454 (10)	−0.0117 (8)	−0.0069 (8)	−0.0170 (8)
C9A	0.0448 (11)	0.0455 (10)	0.0455 (11)	−0.0031 (8)	−0.0092 (9)	−0.0182 (8)
C10	0.0415 (11)	0.0475 (11)	0.0477 (11)	−0.0034 (8)	−0.0100 (9)	−0.0143 (9)
C8A	0.0474 (12)	0.0452 (10)	0.0490 (11)	−0.0063 (9)	−0.0105 (9)	−0.0149 (9)
C5A	0.0470 (12)	0.0375 (10)	0.0549 (12)	−0.0007 (8)	−0.0098 (9)	−0.0141 (9)
C4A	0.0451 (11)	0.0397 (10)	0.0475 (11)	−0.0045 (8)	−0.0080 (9)	−0.0134 (8)
C3	0.0522 (13)	0.0527 (12)	0.0458 (11)	−0.0063 (9)	−0.0116 (9)	−0.0158 (9)
C1	0.0463 (12)	0.0547 (12)	0.0450 (11)	−0.0090 (9)	−0.0070 (9)	−0.0167 (9)
C2	0.0418 (11)	0.0445 (10)	0.0501 (12)	−0.0012 (8)	−0.0110 (9)	−0.0167 (9)
C4	0.0488 (12)	0.0546 (12)	0.0445 (11)	−0.0088 (9)	−0.0032 (9)	−0.0167 (9)
C5	0.0579 (14)	0.0512 (12)	0.0554 (13)	−0.0120 (10)	−0.0028 (10)	−0.0165 (10)
C8	0.0624 (14)	0.0589 (13)	0.0561 (13)	−0.0117 (11)	−0.0156 (11)	−0.0196 (10)
C6	0.0619 (15)	0.0591 (14)	0.0774 (18)	−0.0218 (12)	−0.0097 (13)	−0.0203 (12)
C7	0.0695 (17)	0.0642 (15)	0.0811 (19)	−0.0205 (13)	−0.0219 (14)	−0.0241 (13)

Geometric parameters (Å, º)

C13—N2	1.463 (3)	C8A—C5A	1.411 (3)
C13—C10	1.523 (3)	C5A—C5	1.408 (3)
C13—H13A	0.9700	C5A—C4A	1.430 (3)
C13—H13B	0.9700	C4A—C4	1.495 (3)
C11—C12	1.514 (4)	C3—C2	1.534 (3)
C11—C10	1.527 (3)	C3—C4	1.538 (3)
C11—H11A	0.9700	C3—H3A	0.9700
C11—H11B	0.9700	C3—H3B	0.9700
N2—H2A	0.8600	C1—C2	1.529 (3)
N2—H2B	0.8600	C1—H1A	0.9700
C12—H12A	0.9600	C1—H1B	0.9700
C12—H12B	0.9600	C2—H2	0.9800
C12—H12C	0.9600	C4—H4A	0.9700
N9—C8A	1.373 (3)	C4—H4B	0.9700
N9—C9A	1.382 (3)	C5—C6	1.371 (3)
N9—H9	0.8600	C5—H5	0.9300
C9A—C4A	1.356 (3)	C8—C7	1.382 (4)
C9A—C1	1.493 (3)	C8—H8	0.9300
C10—C2	1.536 (3)	C6—C7	1.395 (4)
C10—H10	0.9800	C6—H6	0.9300
C8A—C8	1.385 (3)	C7—H7	0.9300
N2—C13—C10	112.42 (18)	C9A—C4A—C5A	106.90 (19)
N2—C13—H13A	109.1	C9A—C4A—C4	122.26 (19)
C10—C13—H13A	109.1	C5A—C4A—C4	130.81 (19)
N2—C13—H13B	109.1	C2—C3—C4	112.18 (18)
C10—C13—H13B	109.1	C2—C3—H3A	109.2
H13A—C13—H13B	107.9	C4—C3—H3A	109.2
C12—C11—C10	114.1 (2)	C2—C3—H3B	109.2
C12—C11—H11A	108.7	C4—C3—H3B	109.2
C10—C11—H11A	108.7	H3A—C3—H3B	107.9
C12—C11—H11B	108.7	C9A—C1—C2	109.09 (18)
C10—C11—H11B	108.7	C9A—C1—H1A	109.9
H11A—C11—H11B	107.6	C2—C1—H1A	109.9
C13—N2—H2A	120.0	C9A—C1—H1B	109.9
C13—N2—H2B	120.0	C2—C1—H1B	109.9
H2A—N2—H2B	120.0	H1A—C1—H1B	108.3
C11—C12—H12A	109.5	C1—C2—C3	109.37 (17)
C11—C12—H12B	109.5	C1—C2—C10	112.13 (18)
H12A—C12—H12B	109.5	C3—C2—C10	114.98 (18)
C11—C12—H12C	109.5	C1—C2—H2	106.6
H12A—C12—H12C	109.5	C3—C2—H2	106.6
H12B—C12—H12C	109.5	C10—C2—H2	106.6
C8A—N9—C9A	107.85 (18)	C4A—C4—C3	110.11 (17)
C8A—N9—H9	126.1	C4A—C4—H4A	109.6
C9A—N9—H9	126.1	C3—C4—H4A	109.6
C4A—C9A—N9	110.46 (19)	C4A—C4—H4B	109.6
C4A—C9A—C1	126.41 (19)	C3—C4—H4B	109.6
N9—C9A—C1	123.07 (19)	H4A—C4—H4B	108.2
C13—C10—C11	112.46 (18)	C6—C5—C5A	118.8 (2)
C13—C10—C2	112.44 (18)	C6—C5—H5	120.6
C11—C10—C2	111.85 (18)	C5A—C5—H5	120.6
C13—C10—H10	106.5	C7—C8—C8A	117.8 (2)
C11—C10—H10	106.5	C7—C8—H8	121.1
C2—C10—H10	106.5	C8A—C8—H8	121.1
N9—C8A—C8	129.2 (2)	C5—C6—C7	122.0 (2)
N9—C8A—C5A	108.23 (18)	C5—C6—H6	119.0
C8—C8A—C5A	122.5 (2)	C7—C6—H6	119.0
C5—C5A—C8A	118.3 (2)	C8—C7—C6	120.6 (2)
C5—C5A—C4A	135.1 (2)	C8—C7—H7	119.7
C8A—C5A—C4A	106.56 (19)	C6—C7—H7	119.7
C8A—N9—C9A—C4A	−0.7 (2)	C4A—C9A—C1—C2	17.2 (3)
C8A—N9—C9A—C1	176.66 (18)	N9—C9A—C1—C2	−159.75 (18)
N2—C13—C10—C11	68.0 (2)	C9A—C1—C2—C3	−47.7 (2)
N2—C13—C10—C2	−164.71 (18)	C9A—C1—C2—C10	−176.46 (16)
C12—C11—C10—C13	−157.4 (2)	C4—C3—C2—C1	65.0 (2)
C12—C11—C10—C2	74.9 (3)	C4—C3—C2—C10	−167.82 (16)
C9A—N9—C8A—C8	−178.1 (2)	C13—C10—C2—C1	78.1 (2)
C9A—N9—C8A—C5A	0.8 (2)	C11—C10—C2—C1	−154.29 (18)
N9—C8A—C5A—C5	−179.38 (18)	C13—C10—C2—C3	−47.7 (2)
C8—C8A—C5A—C5	−0.4 (3)	C11—C10—C2—C3	79.9 (2)
N9—C8A—C5A—C4A	−0.7 (2)	C9A—C4A—C4—C3	12.7 (3)
C8—C8A—C5A—C4A	178.36 (19)	C5A—C4A—C4—C3	−169.88 (19)
N9—C9A—C4A—C5A	0.3 (2)	C2—C3—C4—C4A	−45.1 (2)
C1—C9A—C4A—C5A	−176.98 (18)	C8A—C5A—C5—C6	0.7 (3)
N9—C9A—C4A—C4	178.23 (18)	C4A—C5A—C5—C6	−177.6 (2)
C1—C9A—C4A—C4	1.0 (3)	N9—C8A—C8—C7	178.2 (2)
C5—C5A—C4A—C9A	178.6 (2)	C5A—C8A—C8—C7	−0.6 (3)
C8A—C5A—C4A—C9A	0.2 (2)	C5A—C5—C6—C7	−0.1 (4)
C5—C5A—C4A—C4	0.9 (4)	C8A—C8—C7—C6	1.2 (4)
C8A—C5A—C4A—C4	−177.5 (2)	C5—C6—C7—C8	−0.9 (4)