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 es ters of 4-methyl- and/or 4-ethylpiperazinyl substituted carboxylic acids we re studied. Corresponding perfluoro(4-fluoro-1-ethylpiperazine) was obtaine d from 1-ethylpiperazine in a small yield along with perfluoro(1-methyl-3-e thylimidazolidine), perfluoro[2-(N,N'-difluoroaminoethyl)-N,N-diethylamine) ] and perfluorotriethylamine. The corresponding mono-basic perfluoroacid fl uorides with a perfluoro(4-alkylpiperazinyl) group were obtained in fair to good yields from the fluorination of methyl esters of 4-alkylpiperazinyl-s ubstituted carboxylic acids. Yields of the targeted perfluoro(4-alkylpipera zinyl) group containing perfluorocarboxylic acid fluorides varied depending on both the type of N-alkyl (alkyl = CH3- or C2H5-) group at the 4-positio n and the (omega -methoxycarbonylalkyl) group at the 1-position of the pipe razine 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 wit h the same carboxylic acid ester group were fluorinated electrochemically. Spectroscopic data as well as physical properties an described for new perf luoro(1,4-dialkylpiperazines) and N-containing perfluorocarboxylic acids wi th a perfluoropiperazinyl group. (C) 2001 Elsevier Science B.V. All rights reserved.