Crystal structure of 3-( 4-hydroxy-3-methoxyphenyl )-7 , 7-dimethyl-7 , 8-dihydrocinnolin-5 ( 6 H )-one

Article history: Received June 25, 2012 Received in Revised form November 6, 2012 Accepted 30 November 2012 Available online 30 November 2012 The title compound 3-(4-hydroxy-3-methoxyphenyl)-7,7-dimethyl-7,8-dihydrocinnolin-5(6H)one (3) was prepared via one-pot three component reaction of 2-(4-hydroxy-3-methoxyphenyl)2-oxoacetaldehyde with dimedone in the presence of hydrazine hydrate and studied by the single crystal X-ray diffraction method. Its structure was also confirmed by IR, H and C NMR spectroscopy. Compound 3 was crystallized in the monoclinic system, space group P21/c, a = 7.921(2) Å, b = 11.566(4) Å, c = 16.986(6) Å, β = 107.338(5)°, V = 1485.5(8) Å, Z = 4, R1 = 0.0559 and wR2 = 0.1253. The crystal structure of 3 also shows a weak interaction between O3 and N2 atoms. © 2013 Growing Science Ltd. All rights reserved.


Introduction
Cinnolines and their derivatives exhibit a broad range of biological activity, such as anticancer, fungicidal, bactericidal, and anti-inflammatory properties. 1 Furthermore, compounds containing a cinnoline fragment demonstrate a series of interesting physical characteristics, such as luminescent and nonlinear optical properties. 2 Hence, the synthesis of cinnoline has been studied for many years. 3ost syntheses of cinnolines involve arenediazonium salts, 4 arylhydrazones, 5 arylhydrazines, 6 and nitriles 7 as their starting materials.Recently, alkynyl-substituted aryltriazene was used as the precursor to prepare cinnoline, 8 however high temperatures or strong acidic conditions were still required.Palladium-catalyzed annulation of alkynes by functionally substituted aryl halides has been demonstrated to be a versatile methodology to construct a wide variety of complicated hetero-and carbocycles. 9Cinnoline frameworks have been recently obtained via palladium catalyzed reaction of 2-iodotriazenes with internal alkynes. 10These procedures often suffer from certain drawbacks such as multi step reactions, harsh reaction conditions and using expensive catalysts.Therefore, these reported annulation reactions prompted us to investigate a single green reaction to prepare cinnoline rings.

Scheme 1
The proposed mechanism for the synthesis of final compound (3) is shown in Scheme 2.

Scheme 2
In the 1 H-NMR spectrum of this compound, the CH on pyridazine ring is very deshielded and resonates at low field.The corresponding proton appears at δ = 8.24 ppm.

Crystal structure determination of 3
The crystal structure of 3 is shown in Fig. 1.Single-crystals of 3 were used for data collection on a Bruker Smart Apex diffractometer using SMART software. 19Suitable 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, 20 the program SADABS was used for the absorption correction. 20The structure was solved by direct methods using SHELXS-97, 21 and difference Fourier syntheses.Full-matrix least-squares refinement against |F 2 | was carried out using the SHELXTL-PLUS, 21 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 3 were deposited to the Cambridge Crystallographic Data Center (entry no.CCDC-894314) 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).

Description of the crystal 3
The crystal structure of 1 and its crystal packing diagram are shown in Figs. 1 and 2, respectively.A summary of the crystal data and experimental details is given in Table 1.The selected bond lengths and angles for 3 are shown in Table 2.The geometry hydrogen bonds are shown in Table 3.The crystal structure of 3 also shows a weak interaction between O3 and N2 atoms.The dimedone and pyridazine rings moieties are not in the same plane together.The torsion angles of C6-C7-C8-C9, C5-C6-C7-C8 are 50.3°and -55.8°, respectively.The angles of C6-C7-C8, C10-C4-C3 and N1-C9-C8 are 108.12,118.9 and 117.06 o respectively.The carbonyl group in dimedone lies in plane of pyridazine ring.The Bond lengths of N1-N2 and N2-C3 are 1.339 and 1.337 respectively for interaction of O3 with N2.The torsion angles of C9-N1-N2-C3, N2-C3-C1'-C2' equals to 0.5° and 2.8°, respectively.Table 2. Selected bond lengths and angles (Å, °) of 3. Bond Table 3. Hydrogen bond geometry in 3 (Å, º).

Table 1 .
Crystal data and structure refinement details for 3.