Sulfonated reduced graphene oxide (rGO-SO3H): A green, sustainable and efficient heterogeneous catalyst for synthesis of pyrazole containing 1,4 dihydropyridine derivatives

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A simple mild, efficient, expeditious and straightforward synthetic methodology has been established toward furnishing of therapeutically important structurally diverse multi-heterocyclic pyrazole containing substituted 1,4-dihydropyridine (1,4-DHP's) derivatives which might be valuable heterocyclic compound because of the existence of pharmaceutically and medicinally important 1,4-dihydropyridine (1,4-DHP) and pyrazole entities. In this reported synthetic strategy, sulfonated reduce graphene oxide was firstly reported as a highly efficient heterogenous carbo-catalyst for one-pot 4-C synthesis of pyrazole based 1,4-dihydropyridine (DHPs) derivatives. The reported sulfonated reduce graphene oxide (rGO-SO3H) offered mild reaction conditions, structural diversity, high atom economy, operational simplicity, high product conversion, high yield (96%) with wide range of substrates within 15–20 min in ethanol at refluxing temperature. Additionally, experiment results revealed that synthesized carbo-catalyst can be recycled and reused efficiently for at least five reaction cycles. All the synthesized compounds were characterized by IR, HRMS, 1H NMR and 13C NMR, spectroscopic techniques.