Polymeric Schiff Bases. IV. The Prototype Syntheses of Schiff Bases by Reactions of Aromatic Acetals with Aromatic Amines or Their Acyl Derivatives

The acetals of aryl aldehydes react with aryl amines to produce Schiff bases in quantitative yields. This reaction was also facile with diamines and diacetals. It involves a two-step elimination of alcohol; kinetic data indicate that k 2 is equal to or greater than k 1 and this complicates the isolation of any intermediate compound. Because of overlap of absorption bands, the existence of intermediates was not confirmed by infrared spectral measurements. Adducts of the acetals and the aniline hydrochlorides were isolated as hydrochlorides; their molecular weights, as well as the products obtained by neutralization, indicated that the intermediate is not a monoalkoxy compound. The acetals react, also, with N-acyl aniline by the elimination k 1 of the alcohol and k 2 of the ester, in which k 1 k 2, to produce Schiff bases in less than quantitative yields. These reactions of acetals with amines and their N-acyl derivatives are of interest in the syntheses of polymers.