K. Srinivasu, M. S. Kumar, A. Ramachandraiah
May 1, 1999
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Indian Journal of Chemistry Section B-organic Chemistry Including Medicinal Chemistry
Abstract
Electrochemical studies of l-cyclopropyl-6-fluoro-I .4-dihydro-7-(N-piperazinyl)-4-oxo-3-quinoline carboxylic acid 5 and it s synthetic precursors . viz.. 2. 4-dichloro-5-fluoroacetophenone 1. 3-cyclopropylamino-2-(2 .4-dichloro-5fluorobenzoyl)acrylic acid methyl ester 2, 7-chl oro- l-cycl opropyl-6-fluoro- 1 ,4 -dihydro-4-oxo-quinoline-3 -carboxylic acid methyl ester 3 and 7-chloro-l-cyclopropyl-6-fluoro-I.4-dih ydro-4-oxo-quinoline-3-carboxylic ac id 4 are reported. Plausible electrochemical mechanism for th e reduction of the series of compounds is suggested based on cyclic vo!tammetry. coulometry and spectral studies. The role of resonance isomerism aided by intramolecular hydrogen bonding and aromaticity. in the electrochemistry of compounds 2-5. is discussed. The acid-base equilibria of the compounds are revi sited based on PCMODEL MMX Molecular Energy Minimisation Software and cyclic voltammetry. An excellent e1ectro anal yti cal meth od in differential pulse polarography for the quantitativ e analys is of the drug 5 and its sy nthetic precursors 14 is developed. l-Cyclopropyl- 6-fluoro-l,4-dihydro-7-(N-piperazi nyl)-4-oxo -quinoline-3- carboxylic acid 5 is an important wide spectrum drug that is vastly used in