6-Methyl-2,4-diphenylquinoline

The molecules of the title compound, C22H17N, are linked by weak interactions, among which the most prominent are C—H⋯π interactions. The dihedral angles between the phenyl rings and the quinoline ring system are 43.3 (3) and 21.4 (3)°. The title product resulted from a three-component reaction of benzaldehyde, 1-ethynylbenzene and p-toluidine via C—H activation of 1-ethynylbenzene catalyzed by CuI in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate.

The molecules of the title compound, C 22 H 17 N, are linked by weak interactions, among which the most prominent are C-HÁ Á Á interactions. The dihedral angles between the phenyl rings and the quinoline ring system are 43.3 (3) and 21.4 (3) . The title product resulted from a three-component reaction of benzaldehyde, 1-ethynylbenzene and p-toluidine via C-H activation of 1-ethynylbenzene catalyzed by CuI in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate.

Comment
Quinolines and their derivatives are very important in medical chemistry because of their extensive occurrence in natural products. Also, quinolines possess a wide spectrum of biological activities. The classic method of quinoline synthesis is Skraup's procedure (Skraup, 1880). The synthesis of the title compound follows a study of transition-metal catalyzed multicomponent reactions which is a powerful synthetic tool to access complex structures from simple precursors by a one-pot procedure (Shi et al., 2004;Park & Alper, 2005).
In the title compound, all the bond lengths are normal (Allen et al., 1987). The angle between both phenyl rings in the structure is 34.6 (3) °. The dihedral angle between the phenyl ring C1-C6 and the ring C14-C21/N1 is 43.3 (3) °. The dihedral angle between the C7-C12 phenyl ring and the C14-C21/N1 ring is 21.4 (3) °.

Experimental
The p-toluidine (1.5 mmol) and benzaldehyde(1.5 mmol) were taken along with a catalytic quantity of CuI (0.45 mmol) in ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (5 ml) (Scheme 2). The resulting mixture was stirred at 298 K for 15 minutes. At this stage 1-ethynylbenzene (1 mmol) was quickly poured into the reaction mixture and the temperature was raised to 404 K, kept at this temperature for 6 hours, then cooled to room temperature. The product was extracted from the reaction mixture by addition of diethyl ether. (It was possible to recover ionic liquid layer and to use it again without any pretreatment.) The combined organic layer was concentrated and the desired product was isolated by silica gel column chromatography(petrol/EtOAc, 20:1). Colourless sheet crystals were recrystallized from the deuterated chloroform CDCl3 by evaporation in the course of several days. Their average size was 2.5-3 mm.

Refinement
Though all the H atoms could be located in the difference electron-density maps, they were placed into the idealized positions and constrained to ride on their parent atoms. The constrained distances: C-H = 0.93 or 0.96 Å for the aryl or the methyl hydrogens, respectively. The hydrogens' isotropic displacement parameters : U iso (H) = 1.2U eq (C) or 1.5U eq (C) for aryl or methyl hydrogens, respectively. In the absence of significant anomalous scattering effects 1413 Friedel pairs have been merged.
supplementary materials sup-2 Figures Fig. 1. The molecular structure with the atom-numbering scheme. The displacement ellipsoids are drawn at the 30% probability level.