Knorr Cyclizations and Distonic Superelectrophiles

摘要

The acid-catalyzed Knorr cyclization has been studied by experimental and theoretical methods.The results of these studies indicate that beta-ketoamides such as acetoacetanilide undergo diprotonation at the two carbonyl oxygen atoms to form distonic superelectrophiles.Direct observation of a dicationic superelectrophile was achieved by low-temperature ~1H,~(15)N,and ~(13)C NMR from FSO3H-SbF5-SO2ClF solutions.In synthetic studies,the Br0nsted superacid CF3SO3H is found to be an effective acid catalyst for the Knorr cyclization.