Polyacrylonitrile fiber with strongly acidic electrostatic microenvironment: Highly efficient and recyclable heterogeneous catalyst for the synthesis of heterocyclic compounds

Abstract Four categories of sulfonic acid functionalized fiber catalysts with different surface microenvironments were synthesized by covalent grafting using polyacrylonitrile fiber (PANF) as the support. After the effect of acid structure on catalytic activity has been investigated by Friedlander reaction, PAN EOS F was chosen for the synthesis of quinolines and coumarin derivatives with high yields and extensive substrate scope (51 examples) in ethanol or water. The effect of electrostatic microenvironment and solvent has been discussed, and a “release-catch-release-catch” catalytic pattern was proposed accordingly. PAN EOS F can be easily recycled for 20 times without any decrease of catalytic activity.