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

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.

In the title compound, C 20 H 18 N 2 O 3 , 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-HÁ Á ÁO and C-HÁ Á ÁO intermolecular hydrogen bonds involving the nitrogroup O atoms as acceptors.

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 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 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).

Experimental
To the nitroalkene (1.74 mmol) in water (10 ml) was added KHSO 4 (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 supplementary materials sup-2 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.

Refinement
The hydrogen atoms were placed in calculated positions with C-H = 0.89Å to 0.98Å, N-H = 0.86Å and refined in the riding model with fixed isotropic displacement parameters: U iso (H) = 1.5U eq (C)for methyl group and U iso (H) = 1.2U eq (C, N) for other groups.
In the crystal, solvent accessible void 42Å 3 is found.

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.