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Abstract
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During recent decades, there has been developed a great interest in using heterogeneous (solid) acid catalysts instead of those homogeneous ones, due to their possible recovery and recycling solids, which results in reducing the environmental impact 1,2. Some applications of solid acids in organic synthesis have been reviewed by Niknam et al. in 2020 3. In this work, we have developed the Hercynite MNPs as a novel heterogeneous support for the immobilization of sulfuric acid to generate a novel magnetic solid acid catalyst. According to the best of our knowledge, this is the first report on the immobilization of the Sulfuric acid (SO3H) groups by Zolfigol’s method on the surface of hercynite as nanomagnetic catalytic support to get a novel solid acid catalyst. While exploring its catalytic activity, we found it suitable in the multicomponent Hantzsch synthesis of a wide range polyhydroquinoline derivatives under solvent-free conditions and the cyclocondensation of aromatic aldehydes with anthranilamide for the synthesis of 2,3-Dihydroquinazolin-4(1H)-ones in ethanol under reflux conditions Scheme 1. Besides, it is worth mentioning that the reactions were highly productive. The role of Sulfuric acid was inevitable as the bare hercynite catalyst failed to make significant impact on the reaction. After the reaction, the catalyst was easily retrieved by magnet and reused for five times with consistent catalytic reactivity. There was also no leaching of Sulfuric acid species in the reaction medium, justifying its true-heterogeneity.
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