Reaction of 2-Aminobenzophenones with Aliphatic Acids in the Presence of Polyphosphoric Acid

The reaction of 2-aminobenzophenones with aliphatic acids, such as acetic acid, propionic acid, n-butyric acid, and bromoacetic acid, in the presence of polyphosphoric acid afforded 6-substituted 2-anilino-4-phenylquinoline derivatives in fairly good yields. Some of these quinolines were acetylated in the usual way, and the products, 2-(N-acetylanilino) quinolines, were treated with sodium ethoxide to give 1-quinolyl-2(1H)-quinolone derivatives. 2-Amino-5-chlorobenzophenone (Ic) reacted with an equimolar amount of 2-acetamido-5-methylbenzophenone to give 2-(2-benzoyl-4-methylanilino)-6-chloro-4-phenylquinoline, which was also obtained from the reaction of 2,6-dichloro-4-phenylquinoline with Ib in the presence of copper powder. It was found that the reaction mechanism in the formation of 2-anilinoquinolines is similar in type to that in Friedlander’s reaction. Furthermore, the structures of the 2-anilinoquinolines are discussed on the basis of our NMR spectral study.