Electrochemical fluorination of 1-ethylpiperazine and 4-methyl- and/or 4-ethylpiperazinyl substituted carboxylic acid methyl esters

Electrochemical fluorination (ECF) of 1-ethylpiperazine and eight methyl esters of 4-methyl- and/or 4-ethylpiperazinyl substituted carboxylic acids were studied. Corresponding perfluoro(4-fluoro-1-ethylpiperazine) was obtained from 1-ethylpiperazine in a small yield along with perfluoro(1-methyl-3-ethylimidazolidine), perfluoro[2-(N′,N′-difluoroaminoethyl)-N,N-diethylamine)] and perfluorotriethylamine. The corresponding mono-basic perfluoroacid fluorides with a perfluoro(4-alkylpiperazinyl) group were obtained in fair to good yields from the fluorination of methyl esters of 4-alkylpiperazinyl-substituted carboxylic acids. Yields of the targeted perfluoro(4-alkylpiperazinyl) group containing perfluorocarboxylic acid fluorides varied depending on both the type of N-alkyl (alkyl=CH3− or C2H5−) group at the 4-position and the (ω-methoxycarbonylalkyl) group at the 1-position of the piperazine ring of the substrate. Higher yields of perfluoroacid fluorides were obtained by the ECF of 4-ethyl substituted piperazine derivatives than of the 4-methyl substituted piperazine derivatives when 4-alkylpiperazines with the same carboxylic acid ester group were fluorinated electrochemically. Spectroscopic data as well as physical properties are described for new perfluoro(1,4-dialkylpiperazines) and N-containing perfluorocarboxylic acids with a perfluoropiperazinyl group.