Electrochemical studies of 1-cyclopropyl-6-fluoro-1,4-dihydro-7-(N-piperazinyl)-4-oxo-3-quinoline carboxylic acid and its synthetic precursors

Electrochemical studies of 1-cyclopropyl-6-fluoro-1,4-dihydro-7-(N-piperazi nyl)-4-oxo-3-quinoline carboxylic acid 5 and its synthetic precursors, viz. , 2, 4-dichloro-5-fluoroacetophenone 1, 3-cyclopropylamino-2-(2,4-dichloro- 5-fluorobenzoyl)acrylic acid methyl ester 2, 7-chloro-1-cyclopropyl-6-fluor o-1,4-dihydro-4-oxo-quinoline-3-carboxylic acid methyl ester 3 and 7-chloro -1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-quinoline-3-carboxylic acid 4 are reported. Plausible electrochemical mechanism for the reduction of the ser ies of compounds is suggested based on cyclic voltammetry, coulometry and s pectral studies. The role of resonance isomerism aided by intramolecular hy drogen bonding and aromaticity, in the electrochemistry of compounds 2-5, i s discussed. The acid-base equilibria of the compounds are revisited based on PCMODEL MMX Molecular Energy Minimisation Software and cyclic voltammetr y. An excellent electro-analytical method in differential pulse polarograph y for the quantitative analysis of the drug 5 and its synthetic precursors 1-4 is developed.