Electrochemical fluorination of aliphatic secondary amines

Electrochemical fluorination (ECF) has been examined for six aliphatic secondary amines: N,N-di-ethylamine, N-ethyl,N-n-propylamine, N,N-di-n-propylamine, N-ethyl,N-iso-propylamine, N,N-di-iso-propylamine, and N-methyl,N-n-butylamine. It was found from these amines that not only the corresponding F-(N-fluoro-N,N-dialkylamines) but also F-imines having the same number of the carbon atoms were formed in low yields. The suppression of the C–N bond cleavage (blocking effect) which is expected to occur during fluorination due to the presence of bulky N-alkyl group was not observed as a result of the ECF of these aliphatic secondary amines. It was also found that the change of the initial solute concentration of N,N-di-n-propylamine did not affect on the product yields, which is usually observed for cyclic secondary amines. Several F-(N-fluoro-N,N-dialkylamines) were treated with triphenylphosphine for conversion into the corresponding F-imines. An imine bond was generated during this defluorination exclusively at the site of the alkyl group with a longer chain length when there were two different alkyl groups present in F-(N-fluoro-dialkylamines).