Design and Fabrication of Novel Polymerized Dual Nature Ionic Liquid as Highly Effective Catalyst for Regioselective Synthesis of Monospiro Derivatives

Abstract

Poly (ionic liquid)s (PILs) are promising candidates in catalytic transformations; however, hyper cross-linked poly ionic liquids have been rarely reported in catalysis field. In this study, we developed a novel hyper cross-linked PIL (HCPIL) as an effective heterogeneous catalyst for regioselective synthesis of monospiro compounds. For this purpose, a new polymerizable ionic liquid (1-(2-methacryloyloxy)et hyl)-3-vinylimidazolium bromide ([MEVIm]Br)) was designed and synthesized with two different natures; that is, ionic monomer and cross-linker agent. The successful construction of dual nature ionic liquid (IL) was confirmed by analytical techniques such as 1H NMR, 13C NMR, elemental, and FTIR. Next, magnetic HCPIL was fabricated using copolymerization of the prepared IL with N, N-methylenebisacrylamide (MBAA) in the presence of a water soluble initiator (4,4‘-azobis(4-cyanopen tanoic acid)) supported on vinyl functionalized Co3O4 nanoparticles (NPs). The results illustrated that the polymerization of ILs and covalent binding onto the magnetic support improved the thermal stability (from 75 to 33% weight loss around 450 C), reusability, catalytic activity, and generated porous structure. Accordingly, the proposed magnetic Co3O4@p[MEVIm]Br composite was investigated as a heterogeneous catalyst for the ultrasound-assisted synthesis of new and known spirooxindole-2-azapyrrolizidines and spiro-2-amino-4H-pyran-oxindoles; and it showed accelerated mass transfer owing to its great porosity, high surface area (170.0 m2/g), and abundant accessible active sites. The applied scalable catalytic protocol has integrated the rules of an ideal biology-oriented synthesis and organic synthesis to access a spiro heterocyclic skeleton. Easy work-up, high regioselectivity, excellent yields (>90%), short reaction time (6–12 min), and green reaction media are the other advantages of the proposed synthetic method.