U. H. Patel, C. G. Dave, M. Jotani
2002
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Abstract
C 3 2 H 2 6 N 2 O , monoclinic, P12,/nl (No. 14), a = 9.146(1) Â, b= 11.463(3) Â, c = 23.423(5) Â, β = 95.49(2)°, V = 2444.5 Â, Z = 4 ,p m = 1.216 gem", Rp(F) = 0.038, wRKf(F) = 0.125, 7=293 K. Source of material The title compound has been synthesized as described in [ 1 ]. Details of the synthesis will be published elsewhere. Tiny plate like crystals of the compound were grown from chloroform-ethanol solution by slow evaporation. Discussion 2-Pyridine class of compounds show a wide spectrum of biological activities and also found to adopt an interesting stereochemistry. To investigate the effect of the substituents of different sizes like dimethyl [2], diethyl [3], dibenzyl [present study] at 1,3 position of the tetrahydropyridine (THP), on the molecular conformation of THP, we report here the molecular structure of one of the series of such steriochemically interesting THP derivative, namely 1,3-dibenzyl-2-oxo-4,6-diphenyl-1,2,3,4-tetrahydropyridine-3-carbonitrUe. THP ring plane has a half-chair conformation with two of its carbon atoms C2 and C3 deviated maximum by -0.329(1) Â and 0.269( 1) Â, respectively from the best plane of the THP ring. Distorted half-chair conformation adopted by THP ring has also been observed for other closely related compounds [2-4]. Both the benzyl groups and the phenyl rings are planar within themselves. Benzyl group C26-C32 at Ν1 and the phenyl ring at para position of N1 stand vertical (dihedral angle is 87.92(5)° and 89.61(5)°, respectively) with the THP ring plane whereas the benzyl group and the phenyl ring at meta and ortho positions of Ν1 are twisted out of the central THP ring by 34.90(7)° and 49.20(6)°, respectively. The marked difference in the dihedral angle appeared to be influenced by their positions on THP ring. The displacement of C19 and C20 atoms of benzyl groups by -1.885(6) Â and -2.557(8) Â, respectively, on the same side from the central THP ring are significant. C—Ν bond 1.137(2) Â and the angle C2-C18-N2 of 175.1 (2)° of the cyano moiety have characteristic values as commonly observed in 3-cyano 2-pyridine derivatives [2,3,5]. Torsional angleCl-C2-C18-N2of-164(2)° defines the coplanar conformation of cyano moiety with THP ring plane. As observed in other pyridine derivatives Ol is remarkably out [6,7] of the best plane (0.53( 1 ) Â) of the central ring. The torsion angles about C2—C18 and C2—C19 bonds (with the values for 1,3-diethyl and 1,3-dimethyl inside the square bracket) are: ¿ C 1 C 2 C 1 8 N 2 = -164(2)° [-126(8)°, 107(5)°], ¿C3-C2-C18-N2 = 74(2)° [113(8)°, -136(5)°], ¿C1-C2-C19-C20 = 47.49(2)° [55.2(4)°, -], ZC3-C2-C19-C20 = 169.21(4)° [179.4(3)°, -]. The drastic difference in the values of torsion angles reveals that the molecular conformation of THP is quite different in all the three compounds. Thus these observations suggest that the size of the substituent influence the molecular * Correspondence author (e-mail: mmjotani@Fediffmail .com)