A green, chemoselective, and efficient protocol for Paal-Knorr pyrrole and bispyrrole synthesis using biodegradable polymeric catalyst PEG-SO 3H in water

Abstract

In water and in the presence of 1 mol % of Poly(ethylene glycol)-bounded sulfonic acid, amines undergo smooth condensation with 2,5-hexadione at room temperature to afford the corresponding pyrroles in good to excellent yields. The sole products were solidified as the reaction proceeded and separated by simple filtration. In addition, bispyrroles were synthesized in excellent yields via this eco-friendly protocol. The method is easy, simple, cost-effective, chemoselective, and environmentally benign that introduces a beautiful example of click chemistry in water. Copyright © 2012 Wiley Periodicals, Inc.