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 pyrano3,2‐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.