Ce(IV) immobilized on halloysite nanotube–functionalized dendrimer (Ce(IV)–G2): A novel and efficient dendritic catalyst for the synthesis of pyridocoumarin derivatives

In this study, a new and stable Ce(IV) immobilized on halloysite nanotube–functionalized dendrimer was designed, synthesized, and characterized using Fourier‐transform infrared, elemental analysis, thermogravimetric analysis, field emission scanning electron microscopy, scanning electron microscopy–energy dispersive X‐ray spectroscopy, transmission electron microscopy, dynamic light scattering, Brunauer–Emmett–Teller, and inductively coupled plasma optical emission spectroscopy techniques. This catalyst was efficiently used for the one‐pot, single‐step multicomponent synthesis of pyrido[3,2‐c]coumarins from 4‐aminocoumarin, aldehydes, and aryl ketones. The efficiency and selectivity of this catalytic system were also evaluated for the synthesis of pyrido[3,2‐c]coumarins from terminal/internal alkynes instead of aryl ketones. In this respect, the regioselectivity of the products was successfully assigned by X‐ray crystallographic analysis. All these reactions were best performed under solvent‐free conditions in the presence of only 0.28 mol% of the catalyst, and such a one‐pot multicomponent synthesis of pyrido[3,2‐c]coumarins is reported for the first time. It is also worth noting that single‐step and short reaction path for the synthesis of a variety of pyrido[3,2‐c]coumarins along with excellent reusability of this dendritic catalyst makes this method economically and environmentally attractive.