N,N’-Bis-(2,5-dimethyl-3-oxo-1-phenyl-2,3-dihydro-1H-pyrazol-4-yl)phthalamide

Abstract

The title compound, N,N’-bis-(2,5-dimethyl-3-oxo-1-phenyl-2,3-dihydro-1H-pyrazol-4-yl)phthalamide has been synthesized by reactions of o-phthaloyl chloride with 4-amino-2,5-dimethyl-1-phenyl-3-oxo-1H-pyrazolone in acetonitrile. The structure of the new compound was characterized by FT-IR, ¹H NMR, ¹³C NMR and mass spectroscopic techniques. Physical parameters of the compound such as melting point, solubility, λ_max were examined.

Introduction

The pyrazole ring has been known as an important framework in a large number of compounds possessing pharmaceutical and agrochemical properties [1,2,3]. In addition, some substituted pyrazolines have constituted an important class of conjugated nitrogen-containing fluorescent compounds [4]. Functionalized N-arylpyrazoles have been shown to exhibit antihyperglycemic, analgesic, anti-inflammatory, sedative, and hypnotic activities [5]. Some phthalic acid diamide derivatives have been used as agricultural and horticultural insecticides [6].

In view of this, we report the convenient preparation of a new representative of this type of compounds, combining both of the above-mentioned structural elements.

Experimental

Reagents and Techniques

The ¹H and ¹³C NMR spectra were recorded on a Bruker AVANCE DPX NMR spectrometer operating at 400 and 101.6 MHz. Infrared absorption spectra were obtained from a Perkin Elmer BX-II Spectrum 100 and are reported in cm⁻¹ units. Melting points were measured on an Electro Thermal IA 9100 apparatus using a capillary tube. LC mass spectra were obtained on an AGILENT 1100 MSD spectrometer with an ion source temperature of 240 °C. o-Phthaloyl chloride, 4-amino-2,5-dimethyl-1-phenyl-3-oxo-1H-pyrazolone, acetonitrile, tetrahydrofuran and acetone were purchased from Merck.

Preparation of the Title Compound

A solution of o-phthaloyl chloride (1.01 g, 5 mmol) in acetonitrile (20 mL) was added dropwise to a solution of 4-amino-2,5-dimethyl-1-phenyl-3-oxo-1H-pyrazolone (2.03 g, 10 mmol) in acetonitrile (20 mL). The mixture was refluxed with stirring for 3 h. The progress of the reaction was controlled by TLC. After cooling the reaction mixture to ambient temperature, the solid was filtered off and recrystallized from tetrahydrofuran/acetone to give the product. The physical and spectral data of the compound are as follows: colorless crystal, yield 2.68 g (88%), melting point: 204–206 °C.

UV-Vis, λ_max: 281 nm (in Me₂SO);

FT-IR : ν_max (cm⁻¹): 3496 (N-H stretching), 3029 (aromatic C-H stretching), 2986 (C-H aliphatic), 1675 (amide, C=O stretching), 1783, 1713 (C=O, pyrazolone), 1490 (N-CO);

¹H NMR (400 MHz, DMSO-d₆) δ ppm: 6.43 (s, 2H, N-H), 8.01 (t, J = 4.3 Hz, 2H, C_phtaloyl-H), 7.95 (d, J = 3.8 Hz, 2H, C_phtaloyl-H); ), 7.92 (t, J = 5.1 Hz, 4H, C_phen.-H), 7.54 (t, J = 3.5 Hz, 2H, C_phen.-H), 7.39 (d, J = 3.2, 4H, C_phen.-H), 3.43 (s, 6H, N-CH₃), 2.08 (s, 6H, C-CH₃);

¹³C-NMR (100 MHz, DMSO-d₆) δ ppm: 168.29 (C=O), 161.49 (C=O), 135.33, 132.81, 130.59 (C_phtaloyl), 136.21, 124.83, 128.69, 126.12 (C_phenyl), 154.90, 100.50 (C_pyrazolone), 35.83 (N-CH₃), 10.87 (C-CH₃);

Anal. Calcd. for C₃₀H₂₈N₆O₄: C, 67.15%; H, 5.26%; N, 15.66%. Found: C, 67.06%; H, 5.31%; N, 15.67%.