Electrochemical fluorination of several 1,4-bis[(methoxycarbonyl)alkyl] substituted piperazines

Four piperazines, having bis[(methoxycarbonyl)alkyl] groups (CH2CH2C(O)OMe (1), CH(CH3)C(O)OMe (2), CH2CH(CH3)C(O)OMe (3) and CH(CH3)CH2C(O)OMe (4) at the 1- and 4-positions of the piperazine ring), were subjected to electrochemical fluorination (ECF). Two bis[(methoxycarbonyl)alkyl] derivatives of N,N′-dimethylethylenediamine (molecular formulae: MeO(O)CH2CH2N(CH3)CH2CH2N(CH3)CH2CH2C(O)OMe (5) and MeO(O)CH(CH3)CH2N(CH3)CH2CH2N(CH3)CH2CH(CH3)C(O)OMe] (6)) were also similarly fluorinated for a comparative study. On ECF of piperazine derivatives (1–4), the corresponding perfluoropiperazines having bis[(fluorocarbonyl)perfluoroalkyl] groups were formed, while the ECF of the substrates 5 and 6 afforded degraded products only. Yields of the targeted di-basic perfluoroacid fluorides containing a perfluoropiperazinyl group varied, depending on the type of bis[(methoxycarbonyl)alkyl] groups at the 1- and 4-positions. The best yield of the di-basic perfluoroacid fluorides was obtained from the ECF of 1,4-bis[2-(methoxycarbonyl)propyl]piperazine (3). Spectroscopic data as well as physicochemical properties are described for new perfluoroacid fluorides and perfluoro(1,4-dialkylpiperazines).