Sulfonated chitosan encapsulated magnetically Fe3O4 nanoparticles as effective and reusable catalyst for ultrasound-promoted rapid, three-component synthesis of spiro-4H-pyrans

Abstract

A facile one-pot protocol for synthesis of spiro-4H-pyrans using sulfonated chitosan-coated Fe3O4 nanoparticles (Fe3O4@CS-SO3H NPs) as an efficient catalyst under ultrasonic condition has been developed. First, the Fe3O4@CS NPs were prepared from the reaction of chitosan with Fe3O4 NPs. Then, the treatment of Fe3O4@CS NPs with chlorosulfonic acid leads to the formation of Fe3O4@CS-SO3H NPs which exerts excellent catalytic activity toward one-pot, three-component synthesis of spiro-4H-pyran derivatives. The core–shell structure and the composition of produced magnetic nanocatalyst were characterized by FT-IR, XRD, VSM, SEM and EDX techniques.