Synthesis of substituted polyhydroquinolines using zinc chromite nanoparticles as a heterogeneous catalyst via the Hantzsch reaction

Polyhydroquinolines are one of the most important groups of nitrogen heterocycles that have attracted considerable interest because of various important pharmacological and therapeutic properties. Some pharmacological activities of polyhydroquinolines are calcium channel blockers, vasodilator, bronchodilator, antiatherosclerotic, antitumor, geroprotective, hepatoprotective, and antidiabetic agents [1,2]. Furthermore, some polyhydroquinolines exhibit other medicinal applications which include platelet antiaggregatory activity, neuroprotectant, and cerebral antischemic activity in the treatment of Alzheimer’s disease. Hantzsch synthesis of polyhydroquinolines is one of the most significant multi-component reactions due to its key role in the production of these pharmacologically useful compounds. This method generally involves one-pot condensation of aldehydes with β-dicarbonyls and amine sources under acidic conditions [3,4]. Zinc chromite nanoparticles were used as a reusable and robust heterogeneous catalyst for one-pot four component synthesis of polyhydroquinoline derivatives via the esteemed Hantzsch reaction using aryl aldehydes, ethyl acetoacetate, dimedone and ammonium acetate under mild reaction conditions in short reaction times and good to excellent yields in ethanol medium (scheme 1). Moreover, the catalyst was also recovered and reused at least four times without significant decrease in its activity.