Fe₃O₄@SiO₂-Sultone: A Novel and Recyclable Magnetic Nanocatalyst for the Efficient Synthesis of 3,4 Dihydropyrano[]Chromenes and 2-Amino-4-Chromene Derivatives.

A green, simple and eco-friendly procedure for the preparation of 3,4-dihydropyrano[]chromenes and 2-amino-4-chromene derivatives is described using Fe₃O₄@SiO₂-Sultone as a novel and efficient magnetic nanocatalyst. All reactions are performed under mild conditions and all products are obtained in high yields during short reaction times. The catalyst can be easily isolated from the reaction mixture by magnetic decantation using an external magnet and reused at least five times without significant degradation in the activity.