Electrochemical Syntheses of Cyclo[n]pyrrole

✍ Scribed by Mihai Buda; Adriana Iordache; Christophe Bucher; Jean-Claude Moutet; Guy Royal; Eric Saint-Aman; Jonathan L. Sessler

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 452 KB
• Volume: 16
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.201000043

✦ Synopsis

Abstract

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.