COMMUNICATION Molecular Structure of Quinolin-1-(2-quinolyl)-2-one mesitylimine: An Unusual Amination Product of 2,4, 6-Trimethylaniline and 2-Chloroquinoline John J. Allen Æ Christopher E. Hamilton Æ Andrew R. Barron Received: 29 June 2008 / Accepted: 29 July 2008 / Published online: 14 August 2008 Ó Springer Science+Business Media, LLC 2008 Abstract The molecular structure of quinolin-1-(2-qui- nolyl)-2-one mesitylimine has been determined. The Buchwald-Hartwig amination of mesitylaniline with two equivalents of 2-chloroquinoline results in dearomatization of one quinoline heterocycle, forming an imine with the mesitylaniline nitrogen and aminating the second 2-chloro- quinoline via the cyclic nitrogen. The mesityl and quinoline moieties are nearly perpendicular to the plane of the central quinolyl structure. Rationalization of the imine formation is found by a consideration of the relative stability of the syn and anti conformations of the reaction intermediate. Crystal data: space group P2 1 /c, a = 12.609(3), b = 15.010(3), c = 12.456(3) A ˚ , b = 112.68(3)°; V = 2,175.3(8) A ˚ 3 , Z = 4, R = 0.0649, wR 2 = 0.1498. Keywords Imine Á Heterocyclic dearomatization Á Palladium catalysis Introduction Multidentate N-donor heterocycles have been shown to have a wide range of applications including pharmaceuti- cals, electronics, materials, and catalysis [1, 2]. Chelating N-heterocycles in particular have been studied as organic light-emitting diodes [3], as well as ligands for transition metal catalysts [4, 5]. Furthermore, they have been shown to hold great potential in Cu-olefin complexes, as they are capable of e - donation to the Cu center, which aids in p * back-bonding to the olefin [6]. We have recently shown [7] that N-functionalized dipyridylamine and diquinolylamine ligands can be prepared via Buchwald-Hartwig amination [8, 9] of 2-bromopyridine and 2-chloroquinoline with substituted anilines. Interestingly, the main product iso- lated for the amination of 2-chloroquinoline with mesitylaniline (MesNH 2 where Mes = 2,4,6-Me 3 C 6 H 2 ) was not the tertiary amine as found for either the less sterically hindered N-(phenyl)-2,2 0 -dipyridylamine or the more sterically hindered N-(2,6-diisopropylphenyl)-2,2 0 - dipyridylamine, but an imine (Scheme 1). Experimental Synthesis of Quinolin-1-(2-quinolyl)-2-one mesitylimine In a drybox, potassium tert-butoxide (785 mg, 7.0 mmol), allyl[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene] palladium(II) chloride (70 mg, 0.12 mmol), and 2-chloro- quinoline (818 mg, 5.0 mmol) were added to a Schlenk flask. To this was added toluene (10 mL) followed by 2,4,6-trimethylaniline (338 mg, 2.5 mmol). The reaction was stirred under nitrogen at 70 °C for 120 h. After cool- ing, Et 2 O (25 mL) was added to the reaction mixture and then washed twice with brine. The organic phase was dried over sodium sulfate before removing solvent in vacuo. The crude product was purified by flash chromatography on silica gel (eluent: 10% ethyl acetate in hexanes). The product was dissolved in hot hexanes and allowed to cool to room temperature. Subsequent cooling to -12 °C over several days resulted in the formation of crystals suitable for X-ray analysis. Yield 0.276 g (28% isolated). IR (ATR, cm -1 ): 3,058 (w, aromatic m C–H ), 3,003 (w, aromatic m C–H ), J. J. Allen Á C. E. Hamilton Á A. R. Barron (&) Department of Chemistry, Rice University, 6100 Main Street, Houston, TX 77005, USA e-mail: arb@rice.edu URL: www.rice.edu/barron 123 J Chem Crystallogr (2008) 38:873–877 DOI 10.1007/s10870-008-9455-2