Electrochemical fluorination of N-containing carboxylic acids - Part 5. Fluorination of the methyl esters of cis-2,6-dimethylmorpholino-group substituted carboxylic acids

Cis-2,6-dimethylmorpholine and its derivatives having an ester group were subjected to electrochemical fluorination. The electrochemical fluorination of cis-2,6-dimethylmorpholine afforded only a small quantity of F-(N-fluoro-2,6-dimethyl-morpholine), whereas the N-(methoxycarbonylalkyl)-substituted cis-2,6-dimethyl-morpholines gave the corresponding F-acid fluorides in fair yields. Cia-and trans-isomerization on two methyl substituents of the morpholine ring occurred through electrochemical fluorination of pure cis-2,6-dimethylmorpholine to give a 1:0.25-0.5 mixture of cia-and trans-isomers having a F-2,6-dimethylmorpholino-moiety. The formation of a seven-membered ring expanded product was confirmed as a by-product in the fluorination of methyl cis-2,6-dimethylmorpholino-acetate. Spectroscopic data as well as physical properties of new nitrogen-containing F-carboxylic acids are presented. (C) 1998 Elsevier Science S.A.