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Note | Regular issue | Vol 48, No. 6, 1998, pp.1221-1227
Published online, 1st January, 1970
DOI: 10.3987/COM-98-8115
Synthesis of Pyrazolo[4,3-c]quinoline-5-oxide by Reductive Cyclization of 4-Acetyl-5-(2-nitrophenyl)pyrazole: Revision of the Reported Structures

Genadiy D. Kalayanov and Joong-Kwon Choi*

*Korea Research Institute of Chemical Technology, P.O. Box 107, Yousung, Taejeon, 305-600, Korea


Cyclocondensation of 3-(2-nitrobenzoyl)pentane-2,4-dione with phenylhydrazine provided 4-(2-nitrobenzoyl)-3,5-dimethyl-1-phenylpyrazole (5) instead of 4-acetyl-3-methyl-5-(2-nitrophenyl)-1-phenylpyrazole (2). Catalytic hydrogenation of 2 resulted in the stepwise formation of 3,4-dimethyl-1-phenylpyrazolo[4,3-c]quinoline-5-oxide (3), 3,4-dimethyl-1-phenyl-1H-pyrazolo[4,3-c]quinoline (12), and 3,4-dimethyl-1-phenyl-4,5-dihydro-1H-pyrazolo[4,3-c]quinoline (13). Alternate routes for reduction of 5 under different conditions and a facile synthesis of 2 are also described.