May-Jun 2007 Synthesis and Spectral Data of Quinoline Products Obtained by Reaction of N-(4-Pyridinyliden)anilines and N-Benzylidenaniline with 2,2-Dimethoxypropane (Kametani Reaction) 551 Vladimir V. Kouznetsov,* Carlos M. Meléndez Gómez, Juan M. Urbina González, Elena E. Stashenko Laboratorio de Química Orgánica y Biomolecular, Escuela de Química, Universidad Industrial de Santander, A.A. 678, Bucaramanga, Colombia. Alí Bahsas and Juan Amaro-Luis Laboratorio de RMN, Grupo de Productos Naturales, Departamento de Química, Universidad de los Andes, Mérida 5101, Venezuela Received March 23, 2006 R N X O O + CH 2 Cl 2 , Δ, 14 h N N R + R NH N N N R + N N R O 1-4 5-8 9-12 13-16 17-20 BF 3 . OEt 2 NH NH O NH O N BF 3 . OEt 2 CH 2 Cl 2 , 14 h, rt 22 23 24 25 X = N, C-H X = N R = H X = N A study on interaction between N-(4-pyridinyliden)anilines 1-4 and 2,2-dimethoxypropane under Kametani reaction conditions was realized. According to the GC-MS analysis of crude reaction, besides the needed 4-methyl-2-(4-pyridinyl)quinolines 5-8, three collateral products: secondary amines 9-12, 4-(2- methylprop-1-enyl)quinolines 13-16 and 4-(2-methoxy-2-methylpropyl)quinolines 17-20 were formed. Unexpected quinolines 13-16 as well the desired quinolines 5-8 were isolated and fully characterized. In contrast, a condensation of N-benzylidenaniline 21 with 2,2-dimethoxypropane afforded a set of different quinoline products. J. Heterocyclic Chem., 44, 551 (2007). INTRODUCTION The quinoline nucleus occurs in several natural compounds [1] and in some pharmacologically active substances [2]. For instance, the 8-(diethylaminohexyl- amino)-6-methoxy-4-methylquinoline is highly effective against the protozoan parasite Trypanosoma cruzy, which is the agent of Chagas' disease [3]. Several antitumoral antibiotics are based on the 2-(2-pyridinyl)quinoline- quinone tricyclic molecule [4]. Many syntheses of quinolines are known, but due to their importance, the development of new synthetic approaches remains an active research area [5]. An acid-mediated cycloaddition between the C=C-N=C azadiene moieties of N-aryl aldimines and nucleophilic olefins like vinyl ethers is one of the most convenient methods for quinoline preparation, which is usually catalyzed by Lewis acids. BF 3 OEt 2 has been mainly used for this purpose since the pioneering work of Povarov [6]. Both Povarov reaction and Kametani reaction [7] can be considered as [4+2] imino Diels-Alder cycloaddition reactions. The latter consists on the interaction between N- aryl aldimines and acetals (mainly, 2,2-dimethoxypropane and 1,1-diethoxypropane) in the presence of Lewis acids. Until now, Kametani reaction is little used in preparation of quinoline derivatives, maybe, because its low efficiency. However, this reaction could become a simple route to various substituted 4-methylquinolines if appropriate acid catalysts would be developed. The acetals are more stable and available than the vinyl ethers or ketene acetals. Keeping in view the above facts, we wanted to prepare new C-2 4-pyridinyl substituted 8-alkyl-4-methylquinolines needed in our investigations on the search for antifungal quinolines [8,9]. Here we report our comparative study on condensation of N-(4-pyridinyliden)anilines and N-benzyl- idenaniline with 2,2-dimethoxypropane under Kametani reaction conditions. RESULTS AND DISCUSSION The selected N-aldimines 1-4 were prepared by refluxing a mixture in dry ethanol of 4-pyridinecarboxy