Synthesis and characterization of a novel nanomagnetic solid carboxylic acid for sustainable synthesis of pyrano[2,3-c]pyrazoles in water

A carboxylic acid-functionalized magnetic nanocatalyst was synthesized through surface modification of Fe3O4 nanoparticles using an alkyl halide–based sialylation agent, followed by grafting with hexamine and subsequent reaction with chloroacetic acid. The resulting nanocomposite was thoroughly characterized using various structural, morphological, and physicochemical techniques to confirm its composition and architecture. The catalyst was then employed in the one-pot synthesis of pyrano[2,3-c]pyrazole derivatives via a multicomponent reaction of hydrazine hydrate, ethyl acetoacetate, and malononitrile with various substituted aryl aldehydes. The reactions proceeded efficiently in water as a green solvent, affording the desired products in good to excellent yields within short reaction times. The products were isolated by simple recrystallization without the need for chromatographic purification. Notably, the catalyst exhibited excellent reusability, being easily recovered using an external magnet and reused for up to six cycles with minimal loss of catalytic performance.