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.