A versatile core–shell hetero-nanostructure catalysed chemo-selective synthesis of β-enamino carbonyl compounds

Abstract

A core–shell hetero-nanostructure comprising a new in situ generated naphthoquinone cobalt complex covalently immobilized on a silica coated magnetite nanosupport has been described for catalyzing the enamination of β-carbonyl compounds. The newly developed catalyst works as a nanoreactor for boosting this reaction and provides unprecedented chemoselective access to the targeted β-enaminoesters as well as β-enaminones. The synergistic covalent incorporation of an organic entity (a flexible spacer) onto an inorganic solid (surface modified support material) imparts a considerable structural rigidity to the catalyst thereby preventing leaching of the active catalytic species as well evidenced by the hot filtration experiment. Elemental survey and core level XPS spectra confirm the presence of the +II oxidation state of cobalt which is the active catalytic species. This work throws light on how catalytic activity can be tuned and “activity, selectivity and recyclability” the three desired features of a green catalyst can be accomplished on a single platform through careful manipulation of interaction between the support material and active metal complex.