Comparative study of chemically immobilized and conventional homogeneous ionic liquids as phase-transfer catalysts for the N-alkylation of heterocyclic compounds

Abstract

Various ionic liquids (ILs) were screened for their phase-transfer catalytic (PTC) activity using the N -alkylation of nitrogen heterocycles as the model reaction. Immobilized ILs behaved extremely well and proved to be far better catalysts than conventional homogeneous PTCs in terms of their stability, easy recovery, and reusability. The investigation also demonstrated that quaternary tetraalkylammonium salts offer very high catalytic activity, whereas aromatic heterocyclic tetravalent nitrogen catalysts (imidazolium- and pyridinium-based salts) were poorly active.