A sustainable gateway to access 1,8-dioxo-octahydroxanthene scaffolds via a surface-engineered halloysite-based magnetically responsive catalyst

Abstract

In the ever-expanding field of nanomaterials research, numerous attempts have greatly contributed towards the innovation of different frontline methodologies for the synthesis of sustainable, low cost and robust catalysts that have aroused scientific interest in the field of heterogeneous catalysis. Enlightened by this objective, an efficient and easily scalable organic–inorganic hybrid magnetically retrievable halloysite nanotube-based copper nanocatalyst was developed via the immobilization of copper complex onto the surface of CPTMS-functionalized magnetic halloysite nanotubes. Combined microscopic and spectroscopic techniques, such as FE-SEM, TEM, XRD, FT-IR, VSM and XPS, were employed to provide valuable insights into the structural, morphological and physicochemical features of the as prepared Cu(II)@DCH@CPTMS@MHNT nanocomposites. The catalytic efficacy of the synthesized heterogeneous catalysts was examined in the multicomponent one-pot synthesis of pharmaceutically interesting diverse 1,8-dioxo-octahydroxanthenes scaffolds without the need for any special additive or intermediate isolation. The illustrations observed in this work not only reveal the outstanding catalytic activity exhibited by the catalyst, but also display some of the other fascinating features, such as ambient reaction conditions, easy work-up, shorter reaction time, broad substrate scope, high turnover number and no use of toxic organic solvents. Besides, the most attractive aspect of the present protocol is that the catalyst could be facilely retrieved with the aid of an external magnetic force and recycled for up to five runs without losing its catalytic activity significantly. Owing to the outstanding catalytic activity, excellent functional group tolerance and facile recovery reusability, it is further envisaged that newly deisgned Cu(II)@DCH@CPTMS@MHNTs could serve as a versatile platform for multipurpose industrially relevant organic transformations to meet the global requirements for sustainable green production and utilization.