Superparamagnetic core‐shell metal–organic framework Fe3O4@Ni‐MOF as efficient catalyst for oxidation of 1,4‐dihydropyridines using hydrogen peroxide

Abstract

AbstractA facile and efficient method was described for oxidation of some 3,5‐diacyl or 3,5‐diester 1,4‐dihydropyridines using H2O2 in the presence of superparamagnetic core‐shell metal–organic framework Fe3O4@Ni‐MOF. The Fe3O4@Ni‐MOF has been obtained by Step‐by‐Step method in which magnetic Fe3O4 magnetic nanoparticles were coated with Ni‐MOF using a mercaptoacetic acid linker. The synthesized catalyst was characterized using thermogravimetric analysis, FT‐IR spectroscopy, powder X‐ray diffraction, field emission scanning electron microscopy and energy‐dispersive X‐ray analysis. The novel superparamagnetic core‐shell metal–organic framework Fe3O4@Ni‐MOF revealed high efficiency for oxidation of various 1,4‐dihydropyridines using hydrogen peroxide. The Box–Behnken design matrix and the response surface method were applied to investigate the optimization of the reaction conditions. The conditions for optimal reaction yield and time were: amount of catalyst ≈17 mmol, temperature ≈78°C and amount of hydrogen peroxide ≈ 1 ml. A variety of 3,5‐diacyl or 3,5‐diester 1,4‐dihydropyridines with different substituted functional groups have been converted to corresponding pyridines with good to excellent isolated yields using H2O2 and Fe3O4@Ni‐MOF. The catalyst was reused up to five times for the oxidation of 1,4‐dihydropyridines without a significant loss in catalytic activity. The short reaction times, simplicity of method, good to excellent yields and reusability of catalyst were some advantages of the proposed procedure.