Abstract
β-Arylaminocrotonaldehydes (3) were prepared by alkaline hydrolysis of 1-arylamino-3-arylimino-1-butenes (2). On treatment with sulfuric acid, β-anilinocrotonaldehyde (3b) and p-methyl- (3a), m-chloro- (3c), and p-chloro- (3d) derivatives were cyclodehydrated to give the corresponding quinaldines in quantitative yields. The protonation of 3 was proved to take place at the oxygen atom on the basis of spectral evidence.The mechanism of the cyclodehydration is discussed.
