114610-23-0Relevant articles and documents
A New Cinnoline Ring Construction by the Reaction of 2-Diaza-3-(2-fluorophenyl)-3-oxopropionates with Tri-n-butylphosphine
Miyamoto, Teruyuki,Matsumoto, Jun-ichi
, p. 1321 - 1327 (2007/10/02)
A new and convenient synthesis of 4-hydroxycinnoline-3-carboxylate derivatives was developed.Reactions of ethyl 2-diazo-3-(2,4,5-trifluorophenyl- 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-trifluorophenyl- and 2,3,4,5-tetrafluorophenyl)-3-oxopropionates (6a and 6c), respectively.When triphenylphosphine was used, the reaction of 2a-c afforded 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 metylhydrazone 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.Keywords - reductive cyclization; 2-diazo-3-oxopropionate; tri-n-butylphosphine; triphenylphosphine; phosphazine; ring construction; cinnoline
