Electrochemical studies of 1-cyc1opropyl-6-fluoro-1,4-dihydro-7 -(N-piperazinyl)-4-oxo-3-quinoline carboxylic acid and its synthetic precursors

Abstract

Electrochemical studies of 1-cyclopropyl-6-fluoro-1,4-dihydro-7-(<i style="mso-bidi-font-style:normal">N</i>-piperazinyl)-4-oxo-3-quinoline carboxylic acid <b style="mso-bidi-font-weight:normal">5</b> and its synthetic precursors. <i>viz.. </i>2. 4-dichloro-5-fluoroacetophenone <b style="mso-bidi-font-weight:normal">1,</b> 3-cyclopropylamino-2-(2.4-dichloro-5-fluorobenzoyl)acrylic acid methyl ester 2, 7-chloro-1-cyclopropyl-6-fluoro-1 ,4-dihydro-4-oxo-quinoline-3-carboxylic acid methyl ester 3 and 7-chloro-l-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-quinoline-3-carboxylic acid <b style="mso-bidi-font-weight:normal">4</b> are reported. Plausible electrochemical mechanism for the reduction of the series of compounds is suggested based on cyclic voltammetry, coulometry and spectral studies. The role of resonance isomerism aided by intramolecular hydrogen bonding and aromaticity, in the electrochemistry of compounds <b style="mso-bidi-font-weight:normal">2-5,</b> is discussed. The acid-base equilibria of the compounds are revisited based on PCMODEL MMX Molecular Energy Minimisation Software and cyclic voltammetry. An excellent e1ectroanalytical method in differential pulse polarography for the quantitative analysis of the drug <b style="mso-bidi-font-weight:normal">5</b> and its synthetic precursors <b style="mso-bidi-font-weight:normal">1-</b>

<b style="mso-bidi-font-weight:normal"><span style="font-size:12.0pt; font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" mso-ansi-language:en-in;mso-fareast-language:en-in;mso-bidi-language:ar-sa"="" lang="EN-IN">4</span></b><span style="font-size:12.0pt;font-family:" times="" new="" roman";mso-fareast-font-family:="" "times="" roman";mso-ansi-language:en-in;mso-fareast-language:en-in;="" mso-bidi-language:ar-sa"="" lang="EN-IN"> is developed.</span>