5,8-Dimethoxy-2-phenyl-1,4-dihydroquinoline-3-carbonitrile

The crystal structure of the title molecule, C18H16N2O2, can be described as two types of crossed layers parallel to the (110) and (10) planes. An intramolecular N—H⋯O hydrogen bond occurs.


Comment
In quinoline and its derivatives it is usually the pyridine ring which is reduced first. Sodium in liquid ammonia converted quinoline to 1,2-dihydroquinoline (Dauphinee et al., 1978). 1,2,3,4-tetrahydroquinoline was obtained by catalytic hydrogenation and by reduction with borane and sodium cyanoborohydride (Srikrishna et al., 1996), 5,6,7,8-tetrhydroquinoline by catalytic hydrogenation over platinum oxide or 5% palladium or rhodium on carbon in triflouroacetic acid (Vierhapper et al., 1975). Vigorous hydrogenation gave cis and trans-decahydroquinoline. The reducing proprieties of hydrazine are due to its thermal decomposition to hydrogen and nitrogen. The heating of hydrazine with aromatic hydrocarbons at 160-280°C effected complete hydrogenation of the aromatic ring. On the other hand, zinc is used to a limited extent for reductions of double bonds conjugated with strongly polar groups and partial reduction of some aromatics. The majority of reductions with zinc are carried out in acids: hydrochloric, sulfuric, formic and especially acetic. In previous works, we were interested in the design and synthesis of new molecules that contain a quinolyl moiety (Benzerka et al., 2008;Ladraa et al., 2009, 2010, Moussaoui et al., 2002Menasra et al., 2005;Belfaitah et al., 2006and Bouraiou et al.,2006, 2007, 2008. In this paper, we report the structure determination of new compound that result from an unwanted reduction of the pyridine ring of 3-cyano-5,8-dimethoxy-2-phenylquinoline. Our attempt to create a tetrazine ring linked quinolyl moiety, using hydrazine in the presence of Cu(NO 3 ) 2 .3H 2 O-Zn, was failed and led to 1,4-dihydro-5,8-dimethoxy-2-phenylquinoline-3-carbonitrile (I).
The molecular geometry and the atom-numbering scheme of (I) are shown in Fig. 1. The asymmetric unit of title compound contains a 1,4-dihydroquinolyl unit bearing a phenyl ring at position C-2, nitril group at C-3 and two methoxy at C-5 and C-8. The two rings of 1,4-dihydroquinolyl moiety are fused in an axial fashion and form a dihedral angle of 0.17 (5)°.
The phenyl ring form also with quinolyl plane a dihedral angle of 45.38 (6)°. The crystal packing can be described by two types of crossed layers which 1,4-dihydroquinolyl ring is parallel to (110) and (-110)planes respectively (Fig. 2). The crystal packing is stabilized by intramolecular hydrogen bond (N-H···O) and Van der Waals interactions, resulting in the formation of a three-dimensional network and reinforcing a cohesion of structure. Hydrogen-bonding parameters are listed in table 1.
The product was purified by column chromatography. Single crystals suitable for X-ray diffraction analysis were obtained by dissolving the corresponding compound in CH 2 Cl 2 /Petroleum ether mixture and letting the solution for slow evaporation at room temperature.
supplementary materials sup-2 Refinement All non-H atoms were refined with anisotropic atomic displacement parameters. All H atoms were localized on Fourier maps but introduced in calculated positions and treated as riding on their parent C atom. Fig. 1. (Farrugia, 1997) the structure of the title compound with the atomic labelling scheme. Displacement are drawn at the 50% probability level.  as those based on F, and R-factors based on ALL data will be even larger.