Synthesis of a new class of pyrazole embedded spirocyclic scaffolds using magnetically separable Fe3O4@SiO2–SO3H nanoparticles as recyclable solid acid support

Abstract

An efficient, green and sustainable methodology for the synthesis of a new class of pyrazole embedded spirocyclic scaffolds has been developed. The method involves the condensation of a tetrone with a variety of arylhydrazones in the presence of Fe₃O₄@SiO₂–SO₃H magnetic nanoparticles (MNPs) as solid supported acid catalyst under solvent-free conditions. An interesting tandem rearrangement of the in situ generated adducts, derived from the acid catalyzed condensation of tetrone and arylhydrazones, leads to the formation of pyrazole embedded spirocyclic scaffolds. The significant advantages of this methodology are the use of solvent-free reaction conditions, employment of simple and easily available starting materials and reagents, good yields of the products with high atom-economy and operational simplicity of the reaction with the use of a magnetically separable and recyclable nano catalyst.