Oxidative aromatization of some 1,4-dihydropyridine derivatives using pyritic ash in eco-sustainable conditions

Hantzsch 1,4-dihydropyridines (Hantzsch 1,4-DHP), first described in 1882, have been extensively utilised as the analogs of NAD(P)H coenzymes to study the mechanism and synthetic-pharmacological potential of various redox processes. In addition, several 1,4- DHP based drugs, such as Nifedipine, Niguldipine, Amlodepine besylate have been recognised as calcium channel blockers for the treatment of cardiovascular diseases, including hypertension. Both during the redox processes and in the course of drug metabolism, 1,4-DHP systems are oxidatively transformed into the corresponding pyridine derivatives. Furthermore, the oxidation of readily accessible Hantzsch 1,4-DHP constitutes the more accesible, at laboratory scale, method to obtain pyridine derivatives with a great spectrum of important properties. Pyritic ashes, a waste material from the metallurgical industry, present a varied composition and multiple phases with potential catalytic activity. Taking into account that the use of some catalytic agents and conditions for the oxidative aromatization of dihydropyridines results in low yields and tedious separation processes, the use of pyritic ash can facilitate the obtaining of derivatives from dihydropyridines under sustainable conditions.

This report describes the preliminary characterization of pyritic ashes and their use as a catalyst for the aromatization process of dihydropyridines. the results allow to corroborate the effectiveness of this industrial waste as a catalyst. All the synthesized derivatives were characterized by NMR and XRD techniques.