Prolinamide functionalized polyacrylonitrile fiber with tunable linker length and surface microenvironment as efficient catalyst for Knoevenagel condensation and related multicomponent tandem reactions

Abstract

A series of new prolinamide polyacrylonitrile fiber catalysts with tunable length of alkyl linker and different linker group were prepared by covalent bonding for the first time and well characterized by mechanical strength, FT-IR, XRD, EA, TGA, SEM and water contact angel. The catalytic activities of these fiber catalysts were evaluated in Knoevenagel condensation and one-pot Knoevenagel-Michael multicomponent tandem reactions to synthesize α, β-unsaturated nitrile and 2-amino-4H-chromene derivatives in water. The result show that the suitable linker length attaching amines to fiber matrix as well as the constructed hydrophobic microenvironment by linker group within the surface layers of fiber materials effectively promotes the reactions. In addition, the good swollen capacity of fiber in solvent ensure that the reaction proceed well. Fiber catalyst PANPA−2F modified by prolinamide with a C2 alkyl chain exhibited the best catalytic performance and can be easily recovered and reused for at least ten consecutive cycles without significant loss of catalytic activity and active sites leaching.