T. Miyamoto, J. Matsumoto
Apr 25, 1988
Citations
0
Influential Citations
15
Citations
Journal
Chemical & Pharmaceutical Bulletin
Abstract
A new and convenient synthesis of 4-hydroxycinnoline-3-carboxylate derivatices was developed. Reactions of ethyl 2-diazo-3-(2, 4, 5-triflurophenyl- and 2, 3, 4, 5-tetrafluorophenyl)-3-oxopropionates (2a and 2c) with tri-n-butylphosphine afforded ethyl 6, 7-difluoro- and 6, 7, 8-trifluoro-4-hydroxycinnoline-3-carboxylates (5a and 5c) and ethyl 2-hydrazono-3-(2, 4, 5-trifluoro-phenyl- and 2, 3, 4, 5-tetrafluorophenyl)-3-oxopropionates (6a and 6c), respectively. When triphenylphosphine was used, the reaction of 2a-c afforded[[l-ethoxycarbonyl-2-oxo-2-(halogenated phenyl)ethylidene]hydrazono]triphenylphosphoranes (3a-c), which were hydrolyzed to give the corresponding hydrazones 6a-c. An alternate and efficient synthesis of 5a and 5c was accomplished by an intramolecular cyclization of 6a and 6c, respectively. A base-catalyzed cyclization of the methylhydrazone 7 gave ethyl 7-chloro-6-fluoro-1-methyl-1, 4-dihydro-4-oxocinnoline-3-carboxylate (8). Possible mechanisms for the reaction of 2 leading to 5 are discussed.