title: Knorr cyclizations and distonic superelectrophiles.
abstract: 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.
authors.affiliation: Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, USA.
authors.forename: Kiran Kumar Solingapuram
authors.initials: KK
authors.lastname: Sai
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Gilbert
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Klumpp
mesh_terms: 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
chemical_list: D000083:Acetanilides; D002412:Cations; D008698:Mesylates; D015363:Quinolones; C012077:trifluoromethanesulfonic acid