Abstract

In this paper, for the first time, naturally occurring dolomitic limestone is employed as a heterogeneous green catalyst for the synthesis of medicinally valuable N-heterocycles, 2-aryl-1-arylmethyl-1H-benzo[d]imidazoles, dihydropyrimidinones/ thiones and 2-amino-4-aryl-3,5-dicarbonitrile-6-sulfanyl-pyridines in good to excellent isolated yields via a rapid construction of C-N, C-C and C-S bond formations in 1:1 ratio of ethanol:H₂O under ultrasound irradiation. Dolomitic limestone is characterized by X-ray diffraction (XRD), FT-IR, Raman and SEM with EDAX analyses. Further, the catalyst is environmentally benevolent, non-toxic, most abundant, easy to handle low catalyst loading and is reused 7 times without significant loss of catalytic activity. Hence, the catalyst is greener alternative for the synthesis of aforementioned N-heterocycles as compared with the existing reported catalysts.

Keywords: Natural dolomitic limestone; ultrasound irradiation; benzimidazoles; dihydropyrimidinones; highly substituted pyridines

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Godugu, K.; Yadala, V. D. S.; Pinjari, M. K. M.; Gundala, T. R.; Sanapareddy, L. R.; Nallagondu, C. G. R. Beilstein Arch. 2020, 202039. doi:10.3762/bxiv.2020.39.v1

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