Diethyl 3,3′-(phenyl­methyl­ene)bis­(1H-indole-2-carboxyl­ate)

Hong-Shun Sun; Yu-Long Li; Ning Xu; Hong Xu; Ji-Dong Zhang

doi:10.1107/S1600536812036239

. 2012 Aug 25;68(Pt 9):o2764. doi: 10.1107/S1600536812036239

Diethyl 3,3′-(phenylmethylene)bis(1H-indole-2-carboxylate)

Hong-Shun Sun ^a,^*, Yu-Long Li ^a, Ning Xu ^a, Hong Xu ^a, Ji-Dong Zhang ^a

PMCID: PMC3435799 PMID: 22969645

Abstract

In the title compound, C₂₉H₂₆N₂O₄, the benzene ring is twisted by 73.5 (5) and 84.9 (3)° with respect to the mean planes of the two indole ring systems; the mean planes of the indole ring systems are oriented at a dihedral angle of 82.0 (5)°. In the crystal, molecules are linked by pairs of N—H⋯O hydrogen bonds into chains.

Related literature

For applications of indole derivatives, see: Poter et al. (1977 ▶); Sundberg (1996 ▶); Chang et al. (1999 ▶); Ge et al. (1999 ▶); Ni (2008 ▶).

Experimental

Crystal data

C₂₉H₂₆N₂O₄
M _r = 466.52
Triclinic,
a = 8.7340 (17) Å
b = 9.871 (2) Å
c = 15.000 (3) Å
α = 76.14 (3)°
β = 83.91 (3)°
γ = 83.09 (3)°
V = 1242.4 (4) Å³
Z = 2
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 293 K
0.30 × 0.20 × 0.10 mm

Data collection

Enraf–Nonius CAD-4 diffractometer
4879 measured reflections
4557 independent reflections
2813 reflections with I > 2σ(I)
R _int = 0.032
3 standard reflections every 200 reflections intensity decay: 1%

Refinement

R[F ² > 2σ(F ²)] = 0.059
wR(F ²) = 0.144
S = 1.00
4557 reflections
316 parameters
2 restraints
H-atom parameters constrained
Δρ_max = 0.33 e Å⁻³
Δρ_min = −0.24 e Å⁻³

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994 ▶); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995 ▶); program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812036239/xu5612sup1.cif

e-68-o2764-sup1.cif^{(24.3KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812036239/xu5612Isup2.hkl

e-68-o2764-Isup2.hkl^{(223.2KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536812036239/xu5612Isup3.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	2.21	2.955 (3)	144
N2—H2A⋯O4ⁱⁱ	0.86	2.07	2.880 (3)	157

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

Acknowledgments

The authors thank the Center of Testing and Analysis, Nanjing University, for assistance with the data collection.

supplementary crystallographic information

Comment

Indole derivatives are found abundantly in a variety of natural plants and exhibit various physiological properties (Poter et al., 1977; Sundberg, 1996). Among them, bis-indolymethane derivatives are found to be kinds of potentially bioactive compounds (Chang et al., 1999; Ge et al., 1999). In recent years, the synthesis and application of bis-indolymethane derivatives have been widely studied. The title compound is one of bis-indolymethane derivatives as a precursor for MRI Contrast Agents (Ni, 2008). We report here its crystal structure.

The molecular structure of the title compound is shown in Fig. 1. The benzene ring is twisted to the two indole rings with the dihedral angles of 73.5 (5) and 84.9 (3)°, respectively. Two indole rings make a dihedral angle of 82.0 (5)° to each other.

As shown in Figure 2, the molecules are linked by paired N—H···O hydrogen bonds into dimers in the crystal lattice. The structural parameters for the intermolecular hydrogen bonds resulting in the formation of dimers are given in Table 1.

Experimental

Ethyl indole-2-carboxylate (18.9 g, 100 mmol) was dissolved in 200 ml ethanol; commercially available benzaldehyde (5.3 g, 50 mmol) was added and the mixture was heated to reflux temperature. Concentrated HCl (3.7 ml) was added and the reaction was left for 1 h. After cooling the white product was filtered off and washed thoroughly with ethanol. The reaction can be followed by TLC (CHCl₃:hexane = 1:1). Yield was 90%. Crystals of the title compound suitable for X-ray analysis were obtained by slow evaporation of an ethanol solution.