Poly (L-phenylalanine-paired ionic liquid) as halogen-free heterogeneous nanocatalyst toward regiospecific 1,3-dipolar cycloaddition reaction

Abstract

Although amino acid-paired ionic liquids (IL [AA]) have attracted considerable attention due to their environmental-friendly nature and providing abundant catalytic active sites, polymerized eco-friendly ILs have been rarely reported. Herein, we introduce a novel polymerized L-phenylalanine-paired ionic liquid (PIL [Phe]), synthesized in a new smart manner, as a promising heterogeneous nanocatalyst for regiospecific 1,3-dipolar cycloaddition reaction. For this purpose, new polymerizable ionic liquid (3-(3-aminopropyl)-1-vinylimidazolium (L)-2-amino-3-phenylpropanoate ([AVIm][Phe])) was designed and constructed as a halogen-free multifunctional monomer. The successful fabrication of chiral IL was approved by different techniques including 1H NMR, FT-IR, and elemental analysis. Next, a green precipitation polymerization approach was applied using a water-soluble initiator under mild conditions. Co3O4@PIL [Phe] was synthesized by in situ copolymerization of the [AVIm][Phe] with ethyleneglycoldimethacrylate (EGDMA) (as non-ionic cross-linker) supported on magnetic Co3O4@MPS. The obtained data reveal that the supported polymerized form of [AVIm][Phe] is more efficient due to the formation of a porous structure with high-specific surface area (235.5 m2/ g) and a cross-linked network with high thermal stability (35% weight loss around 600 °C). In the following, the proposed Co3O4@PIL [Phe] nanostructure was applied as a magnetic catalyst toward the preparation of new and reported pyrrolidinyldispirooxindoles; and it displayed accelerated mass transfer due to its large pore volume (0.85 cm3/ g), and numerous accessible active sites. Consequently, a range of pharmaceutical dispirobisoxindole scaffolds with broad structural diversity were readily obtained in excellent yields (>92%) and high regioselectivity under environmental conditions.