Abstract
Natural dolomitic limestone (NDL) is employed as a heterogeneous green catalyst for the synthesis of medicinally valuable benzimidazoles, dihydropyrimidinones, and highly functionalized pyridines via C–N, C–C, and C–S bond formations in a mixture of ethanol and H2O under ultrasound irradiation. The catalyst is characterized by XRD, FTIR, Raman spectroscopy, SEM, and EDAX analysis. The main advantages of this methodology include the wide substrate scope, cleaner reaction profile, short reaction times, and excellent isolated yields. The products do not require chromatographic purification, and the catalyst can be reused seven times. Therefore, the catalyst is a greener alternative for the synthesis of the above N-heterocycles compared to the existing reported catalysts.
Highlights
Nitrogen heterocycles are recognized as “privileged medicinal scaffolds” because these compounds are found in a wide variety of bioactive natural products and pharmaceuticals [1,2,3]
The rock formation in the mineralized area of this village belongs to the Vempalli Formation (VF) of the Papaghni group of the lower Cuddapah Supergroup in the Cuddapah Basin (CB)
The same reaction was repeated in the presence of the Natural dolomitic limestone (NDL) catalyst (5.0 wt %) in EtOH/H2O 1:1 under ultrasound irradiation at 45–50 °C for 15 min, which resulted in 97 % yield of 7a
Summary
Nitrogen heterocycles are recognized as “privileged medicinal scaffolds” because these compounds are found in a wide variety of bioactive natural products and pharmaceuticals [1,2,3]. To achieve the target compound 3a, the same reaction was repeated by employing various catalysts (2.5 wt %), such as Fe2O3, Al2O3, KF–alumina, dolomitic limestone, triethylamine, pyridine, and DABCO in different solvents, such as water, acetone, iPrOH, EtOH, and EtOH/H2O 1:1 (Table 2, entries 2–8) under ultrasound irradiation at 45–50 °C.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
