Electrochemical syntheses of cyclo[n]pyrrole.
Cyclo[8]pyrrole was obtained efficiently when 3,3',4,4'-tetraethylbipyrrole was subjected to bulk electrolysis, with yields spanning a range from close to 0 % with tetra-n-butylammonium fluoride as the electrolyte, to almost 70 % when tetra-n-butylammonium hydrogensulfate was used for this purpose. These observations are consistent with the conclusion that the reaction is controlled by anion-related factors such as a specific templating effect. Note that cyclo[8]pyrrole was the only detectable macrocyclic product obtained from 3,3',4,4'-tetraethylbipyrrole under the conditions of the electrochemical oxidation. When similar electrolyses were performed by using 3,4-diethylpyrrole as the starting material, two products could be isolated, which were identified as being the cyclo[7]pyrrole and cyclo[8]pyrrole, respectively. Detailed analyses of the oxidized forms of cyclo[7]pyrrole and cyclo[8]pyrrole revealed that under the conditions of the electrolysis these latter species are not stable.
Buda
Mihai
M
Département de Chimie Moléculaire, Laboratoire de Chimie Inorganique Rédox, UMR-5250, Université Joseph Fourier, BP 53, 38041, Grenoble Cédex 9, France.
Iordache
Adriana
A
Bucher
Christophe
C
Moutet
Jean-Claude
JC
Royal
Guy
G
Saint-Aman
Eric
E
Sessler
Jonathan L
JL