Single crystal X-ray structure of 3-amino-5-( 4-chlorophenyl ) pyridazine-4-carbonitrile

Article history: Received March 27, 2013 Received in Revised form August 27, 2013 Accepted 17 October 2013 Available online 18 October 2013 The title compound 3-amino-5-(4-chlorophenyl)pyridazine-4-carbonitrile was prepared by a one-pot three-component reaction of malononitrile with corresponding arylglyoxal in the presence of hydrazine hydrate at room temperature in water and ethanol. Its structure was also confirmed by its IR, H, C-NMR, Mass spectral data and elemental analysis. The compound was crystallized in the monoclinic system, space group P21/c, a = 3.817(3) Å, b = 13.533(10) Å, c = 19.607(15) Å, β = 93.401(10)°, Z=4, R1 = 0.0906 and wR2 = 0.1422. The crystal structure of the compound also shows a weak intermolecular interaction between N1 atom of one molecule and N3 atom of the other molecule. © 2013 Growing Science Ltd. All rights reserved.


Introduction
In recent years, a great deal of current interest is focused on development of novel multicomponent reactions, 1 due to the simplicity of a one-pot procedure, the possible structural variation, the accessible complexity of the molecules, straightforward reaction design, and the environmental friendliness.Among one-pot synthetic methods, multicomponent reactions, leading to nitrogen-containing heterocyclic compounds have been indispensable structural unit for both organic chemists and biochemists because of their biological and pharmaceutical properties.The pyridazine fragment is an important pharmacophore and is known to exhibit promising biological properties such as analgesics, 2 insecticidals, 3 fungicidals, 4,5 cardiotonics 6 and bacteriocides. 7[10][11][12][13][14] In continuation of recent reports on synthesis of pyridazine derivatives, [15][16][17][18][19][20][21][22][23] we would like to report the single crystal X-ray structure of 3-amino-5-(4-chlorophenyl)pyridazine-4-carbonitrile prepared by a one-pot three-component reaction of malononitrile with corresponding arylglyoxal in the presence of hydrazine hydrate at room temperature. 23

Results and Discussion
The arylglyoxal 1 was prepared from 4-chloroacetophenone 24 and used in the synthesis of the compound 2, as shown in Scheme 1.To confirm this, the preparation of 2 was carried out in two stages, with the isolation of the hydrazone 3, which was then reacted with malononitrile, leading to the formation of the product 2.The spectral data of 2 prepared by the two stages method was identical with that produced in the one pot sequence.

Scheme 1
The proposed mechanism of the formation of 2 is shown in Scheme 2.

Scheme 2 Crystal structure determination of 2
The crystal structure of 2 is shown in Fig. 1.Single-crystals of compound 2 were used for data collection on a Bruker Smart Apex diffractometer using SMART software. 25Suitable crystals were selected and mounted on a glass fiber using epoxy-based glue.The data sets were collected at room temperature for sample employing a scan of 0.3° in ω with an exposure time of 20 s/frame.The cell refinement and data reduction were carried out with SAINT, 26 the program SADABS was used for the absorption correction. 26The structure was solved by direct methods using SHELXS-97, 27 and difference Fourier syntheses.Full-matrix least-squares refinement against |F 2 | was carried out using the SHELXTL-PLUS, 27 suit of programs.All non-hydrogen atoms were refined anisotropically.Hydrogen atoms were placed geometrically and held in the riding mode during the final refinement.The crystallographic data for structure 2 were deposited to the Cambridge Crystallographic Data Center (entry no.CCDC-948077) and are available free of charge upon request to CCDC, 12 Union Road, Cambridge, UK (Fax: +44-1223-336033, e-mail: deposit@ccdc.cam.ac.uk).Table 3. Hydrogen bond geometry in 2 (Å, º).

3-Amino-5-(4-chlorophenyl)pyridazine-4-carbonitrile (2)
A mixture of 4-chloroacetophenone (1 mmol) and hydrazine hydrate (4 mmol) in water and ethanol (1:1) (3 mL) was stirred at room temperature for 30 min.Then malononitrile (1 mmol) was added to the reaction mixture and was stirred for a further 30 min at room temperature.The product was then collected as a white precipitate, washed with hot water, and purified by recrystallization from ethanol to give the title compound as white solid (Yield: 87%), mp 290 ºC (dec.

Table 1 .
Crystal Data and Experimental Details for 2.