Novel ZnO‐Co ₃ O ₄ ‐CuO Nanocomposite Catalyzed Microwave‐Assisted Facile Synthesis of Polyhydroquinoline Derivatives

ABSTRACT A novel ZnO‐Co 3 O 4 ‐CuO nanocomposite (NC) has been explored as a heterogeneous catalyst for synthesizing a library of polyhydroquinolines (PHQ 1–10) via microwave‐assisted multicomponent reaction of various aromatic aldehydes, ethyl acetoacetate or ethyl cyanoacetate, dimedone, and ammonium acetate at 400 W in polyethylene glycol (10 mL) as a solvent. The NC showed a characteristic weak ferromagnetic behavior with a particle size of 10.3 ± 0.1 nm and surface area of 45.67 m 2 /g was easily prepared through a straightforward chemical coprecipitation method and was systematically characterized using XRD, FTIR, FESEM, HRTEM, EDS, BET, and VSM. The NC has an agglomerated particle cluster having a nearly spherical shape exhibiting brilliant catalytic performance, over +12.94 mV zeta potential value, hydrodynamic diameter of 267 nm, best dispersion stability, and reusability for up to six runs. This method of synthesizing PHQs has notable advantages of producing higher yields in a shorter reaction time (20 min), using simple, low‐cost catalyst, and microwave irradiation as a non‐conventional energy source. The highest TON of 37.76 and TOF of 113.29 h −1 also indicate that this is the best atom‐efficient and green design for the synthesis of polyhydroquinolines. Some novel polyhydroquinolines were also synthesized with excellent yield.