Knorr cyclizations and distonic superelectrophiles.
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, 15N, and 13C NMR from FSO3H-SbF5-SO2ClF solutions. In synthetic studies, the Brønsted superacid CF3SO3H is found to be an effective acid catalyst for the Knorr cyclization.
Sai
Kiran Kumar Solingapuram
KK
Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, USA.
Gilbert
Thomas M
TM
Klumpp
Douglas A
DA
D000083:Acetanilides / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D003500:Cyclization; D004563:Electrochemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods / Q000592:standards; D008698:Mesylates / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure; D015363:Quinolones / Q000138:chemical synthesis / Q000737:chemistry; D012015:Reference Standards
D000083:Acetanilides; D002412:Cations; D008698:Mesylates; D015363:Quinolones; C012077:trifluoromethanesulfonic acid