Cobalt ferrite encapsulated in a zwitterionic chitosan derived shell: An efficient nano‐magnetic catalyst for three‐component syntheses of pyrano[3,2‐c]quinolines and spiro‐oxindoles

A nano‐magnetic core‐shell composite fabricated of a unique zwitterionic chitosan‐derived coating and cobalt ferrite core was found to be a green and reusable heterogeneous catalyst for efficient synthesis of pyrano[3,2‐c]quinoline and spiro‐oxindole derivatives in high to excellent yields. Due to having negative charges at its outermost layer and a high magnetization, the catalyst is finely dispersed in ethanol and can be easily separated from reaction mixtures by using a simple external magnet. It is reasonably stable as can be reused several times without appreciable loss of catalytic activity. Cobalt ferrite nano‐particles encapsulated with the chitosan derivative containing 12% of the zwitterionic N‐(4‐sulfonylbutyl) grafts have shown good dispersity in ethanol and water. The IR spectrum of this nano‐composite is better interpreted as displaying the formation of covalent bonds between its inorganic and bioorganic components. The nano‐composite appeared as a soft and efficient catalyst in the synthesis of pyrano[3,2‐c]quinolin‐4‐ones.