2-Methyl-3-{2-nitro-1-[2-(prop-2-yn-1-yl­oxy)phen­yl]eth­yl}-1H-indole

P Narayanan; K Sethusankar; K Ramachandiran; P T Perumal

doi:10.1107/S1600536811036907

. 2011 Sep 17;67(Pt 10):o2658. doi: 10.1107/S1600536811036907

2-Methyl-3-{2-nitro-1-[2-(prop-2-yn-1-yloxy)phenyl]ethyl}-1H-indole

P Narayanan ^a, K Sethusankar ^a,^*, K Ramachandiran ^b, P T Perumal ^b

PMCID: PMC3201230 PMID: 22058778

Abstract

In the title compound, C₂₀H₁₈N₂O₃, the indole unit is essentially planar, with a maximum deviation of 0.0197 (18) Å for the N atom and forms a dihedral angle of 78.09 (9)° with the propyne-subsituted phenyl ring. The propyne group is almost linear, the C—C C angle being 176.5 (2)°, and is also in the flagpole position on the O atom. In the crystal, molecules are linked via N—H⋯O and C—H⋯O intermolecular hydrogen bonds involving the nitro-group O atoms as acceptors.

Related literature

For general backround to indoles, see: Gribble (1996 ▶); Mathiesen et al. (2005 ▶). For related structures, see: Narayanan et al. (2011 ▶); Ranjith et al. (2010 ▶). For bond-length distortions, see: Allen (1981 ▶).

Experimental

Crystal data

C₂₀H₁₈N₂O₃
M _r = 334.36
Tetragonal,
a = 23.3474 (7) Å
c = 12.8536 (7) Å
V = 7006.5 (5) Å³
Z = 16
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 295 K
0.30 × 0.25 × 0.20 mm

Data collection

Bruker Kappa APEXII diffractometer
31091 measured reflections
3954 independent reflections
2629 reflections with I > 2σ(I)
R _int = 0.034

Refinement

R[F ² > 2σ(F ²)] = 0.049
wR(F ²) = 0.149
S = 1.03
3954 reflections
231 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.35 e Å⁻³
Δρ_min = −0.30 e Å⁻³

Data collection: APEX2 (Bruker, 2008 ▶); cell refinement: SAINT (Bruker, 2008 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 (Farrugia, 1997 ▶) and Mercury (Macrae et al., 2008 ▶); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536811036907/rk2291sup1.cif

e-67-o2658-sup1.cif^{(20.2KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811036907/rk2291Isup2.hkl

e-67-o2658-Isup2.hkl^{(190.2KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811036907/rk2291Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1A⋯O2ⁱ	0.86	2.14	2.997 (2)	173
C11—H11A⋯O1ⁱⁱ	0.97	2.52	3.433 (3)	157
C15—H15⋯O1ⁱⁱⁱ	0.93	2.57	3.315 (3)	137

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) .

Acknowledgments

PN and KS thank Dr Babu Varghese, SAIF, IIT, Chennai, India, for the X–ray intensity data collection and Dr V. Murugan, Head of the Department of Physics, for providing facilities in the department to carry out this work.

supplementary crystallographic information

Comment

Indole is a common motif for drug target and as such, of new diversity–tolerant routes to this previleged biological scaffold continues to be of significant benefit (Gribble, 1996) and forms the basis of a wide variety of drugs, including the anti–inflammatory agent indomethacin, reserpine and sumatriptan. Indole derivatives are identified as interfering with a G protein–independent signalling pathway of the CRTH2 receptor (Mathiesen et al., 2005). As a part of our studies, we report herein the crystal structure of the title compound, which comprises the bicycle indole moiety, propyne subsituted phenyl ring and nitro methane group, as illustrated in (Fig. 1).

In the title compound, C₂₀H₁₈N₂O₃, the indole bicycle moiety (C1–C8/N1) is essentially planar with a maximum deviation of -0.0197 (18)Å for N1 atom. The indole moiety (C1–C8/N1) forms a dihedral angle of 78.09 (9)° with the propyne subsituted phenyl ring (C12–C17). In the indole ring system, the dihedral angle between the pyrrole ring (C5–C8/N1) and benzene ring (C1–C6) is 1.17 (10)°.

In the indole moiety, the endocyclic angles at C4 and C6 are contracted to 117.5 (2)° and 118.0 (17)°, respectively, while those at C2, C3 and C5 are expanded to 121.5 (2)°, 121.6 (3)° and 121.2 (3)°, respectively. This would appear to be a real effect caused by the fusion of the smaller pyrrole ring to the six–membered benzene ring, and the strain is taken up by the angular distortion rather than by bond–length distortions (Allen, 1981).

The angles around atom C10: [C7—C10—C12 = 113.88 (13)°, C7—C10—C11 = 110.41 (14)° and C12—C10—C11 = 109.95 (14)°] deviates significantly from ideal tetrahedral values which may be as a result of steric interactions between indole, nitromethane and propyne subsituted phenyl ring. The deviation of atom C10 from the indole moiety is -0.1066 (16)Å. The deviations of atom O3 from the phenyl ring (C12–C17) and propyne group (O3/C18/C19/C20) are 0.0504 (14)Å and 0.3088 (14)Å, respectively.

The oxygen subsituted propyne group is slightly twisted from the phenyl ring (C12–C17) which it is attached as evindenced by the torsion angle C16–C17–O3–C18 = 7.2 (3)°. The propyne group is almost linear, C18–C19≡C20 angle being 176.5 (2)°, and is also in the flagpole position on O3 atom. The title compound exhibits structural similarities with the already reported related structures (Narayanan et al., 2011; Ranjith et al., 2010).

In the crystal packing, molecules are linked via N—H···O and bifurcated C—H···O intermolecular hydrogen bonds involving the nitro group O atoms as acceptors (Table 1). The symmetry codes are: (i) -y+3/4, x-1/4, -z+3/4; (ii) -y+5/4, x-1/4, z-1/4; (iii) y+1/4, -x+5/4, z-3/4. The packing view of the title compound is shown in (Fig. 2).

Experimental

To the nitroalkene (1.74 mmol) in water (10 ml) was added KHSO₄ (30 mol%) and the mixture was stirred for 5 minutes. 1–Ethyl–indole (1.74 mmol) was added to the mixture and the stirring was continued following the progress of the reaction by TLC. After completion of the reaction, the reaction mixture was extracted with ethyl acetate (3× 10 ml), dried over anhydrous sodium sulfate, filtered, concentrated under reduced pressure and the residue was column chromatographed over silica gel using EtOAc : Petroleum ether (1.5 : 8.5) as eluent to get the pure product.