Magnetic cellulose nanocrystals as efficient support for indium(III) in the synthesis of tetrazoles and phthalazines

Abstract

Catalysts, especially heterogeneous catalysts, play an essential role in organic transformation reactions. Hence, we use a composite of cellulose nanocrystals (CNC) and Fe3O4 NPs as new support for indium(III) and evaluate the performance of fabricated Fe3O4/CNC-In(III) catalyst in the synthesis of two different heterocyclic compounds: Tetrazole and phthalazine derivatives. Although metal oxides and metal NPs are in the spotlight due to their excellent catalytic activity, they are limited in application due to their self-agglomeration in the reaction mixture, resulting in reduced performance. The addition of CNC to Fe3O4 NPs due to rich-hydroxyl sites on the CNC surface and its interaction turns Fe3O4/CNC into a stable and appropriate substrate for the immobilization of indium(III). The formation and physicochemical properties of the catalyst were endorsed by FT-IR, SEM, TEM, EDS, XRD, TGA, and elemental mapping analysis. In addition, the synthesis of substituted 2-(1H-tetrazole-5-yl) acrylonitrile and 2H-indazolo[2,1-b]phthalazinetriones was performed under solvent-free conditions; this feature is another advantage of the current procedure. Utilization of sustainable natural materials and low-cost chemicals, short reaction time, high catalytic activity, magnetic feature and easy separation with external magnet, excellent reusability without showing substantial activity loss for six runs, and uniform distribution are some of the significant advantages of this catalyst.