Ethyl 3-{2-[(3-Methyl-1H-indol-2-yl)carbonyl]­hydrazinylidene}­butanoate

Abstract

The title compound, ethyl 3-{2-[(3-methyl-1H-indol-2-yl)carbonyl]hydrazinylidene}butanoate (3), was prepared via reaction of 3-methyl-1H-indole-2-carbohydrazide (1) and ethyl 3-oxo¬butanoate (2) under reflux. The structure of the synthesized compound was assigned on the basis of elemental analysis, IR, ¹H-NMR, mass spectral and X-ray data.

Indoles are among the most important nitrogen-containing heterocyclic molecules, found extensively in biological systems which play a vital role in biochemical processes. The indole ring system is found in many natural products, pharmaceutical agents and polymer materials [1,2,3,4,5,6,7]. The interesting chemical properties of indole have inspired chemists to design and synthesize a variety of indole derivatives [8]. In view of this finding, in the present paper we describe the synthesis of a new indole derivative with expected biological activity.

Results and Discussion

3-Methyl-1H-indole-2-carbohydrazide (1) [9] was allowed to react with ethyl 3-oxobutanoate (2) in ethanolic solution under reflux. The expected product of this reaction was assumed to be one of the seven structures 3–9 shown in Scheme 1. IR, ¹H-NMR, mass spectral data and single-crystal X-ray diffraction studies (Figure 1 and

Table 1. Selected bond lengths and bond angles in the ORTEP representation of compound 3 in the crystal. The crystallographic numbering does not reflect systematic numbering.

Bond length, Å	Bond length, Å	Bond length, Å
C7—C15, 1.472	N6—C14, 1.286	C12—C17, 1.517
N5—C7, 1.359	C14—C21, 1.487	O1—C17, 1.337
N5—N6. 1.380	C12—C14, 1.493	O1—C20, 1.450
Angle (ω)	Angle (ω)	Angle (ω)
C17—O1—C20, 115.7	O2—C7—N5, 117.4	N23—C10—C8, 108.4
C10—N23—C15, 108.5	O2—C7—C15, 120.3	N23—C10—C13, 129.4
N6—N5—C7, 121.0	N5—C7—C15, 122.3	C8—C10—C13, 122.2

) of the isolated product were in full agreement with the structure 3, but not with the other structures 4–9.

Crystallographic Analysis

The crystals were mounted on a glass fiber. All measurements were performed on an ENRAF NONIUS FR 590. The data were collected at a temperature of 25 °C using the ω scanning technique to a maximum of a 20 of 22.986°. The structure was solved by direct method using SIR 92 and refined by full-matrix least squares. Non-hydrogen atoms were refined anisotropically. Hydrogen atoms were located geometrically and were refined isotropically [10].

Crystal Data for Compound 3

C₁₆H₁₉N₃O₃, M = 301.346, monoclinic, a = 19.3108 (8), b = 7.7168 (4), c = 21.0944 (10) A^o, v = 3131.2 (3), α = γ = 90.00°, β = 95.065 (3)°, space group: P2₁/c, Z=8, D_x = 1.279 Mg m⁻³ reflection 937 measured, θ_max = 27.50°. Figure 1 illustrates the structure as determined [10].

Synthesis of Ethyl 3-{2-[(3-Methyl-1H-indol-2-yl)carbonyl]hydrazinylidene}butanoate (3)

A mixture of the hydrazide 1 (1.89 g, 10 mmol) and ethyl 3-oxobutanoate 2 (10 mmol) in absolute ethanol (20 mL) was heated at reflux temperature for 2 h. The reaction mixture was then cooled and the formed precipitate was filtered off, washed with ethanol to afford the title compound 3. Yield: 84%; yellow microcrystals (from ethanol); mp: 238–240 °C. IR (KBr): v 1706, 1668 (2 C=O), 3409, 3234 (2 NH) cm⁻¹. ¹H NMR (DMSO-d₆): δ 1.24 (t, J = 7.0 Hz, 3H, CH₃), 2.03 (s, 3H, CH₃), 2.53 (s, 3H, CH₃), 3.43 (s, 2H, CH₂), 4.23 (q, J = 7.0 Hz, 2H, CH₂), 6.87–7.98 (m, 4H, ArH ), 10.38 (s, 1H, D₂O exchangeable, NH), 11.21 (s, 1H, D₂O exchangeable, NH). MS m/z (%): 301 (M⁺, 42), 189 (100), 155 (318), 117 (46), 77 (21).

Anal. Calcd for C₁₆H₁₉N₃O₃ (301.34): C, 63.77; H, 6.36; N, 13.94. Found C, 63.39; H, 6.46; N, 13.65.