In the chemistry world, the year 1891 was considered as milestone year for the discovery of new type of heterocyclic compounds by Pietro Biginelli. The Biginelli protocol provides 3,4-dihydropyrimidin-2(1H)-ones/thiones in the presence of Bronsted acids and Lewis acids. Multifunctional Dihydropyrimidones (DHPMs) are displayed wide medicinal properties. Several of homogeneous and heterogeneous catalysts have been reported to improve the yield of product. This review includes the progress of ionic liquids, combination of ionic liquids with homogeneous & heterogeneous catalyst, homogeneous, heterogeneous and asymmetric catalyst took place in last five year (2015-2019) for Biginelli reaction. Most of catalysts showed good catalytic activity (more than 80 %) towards the synthesis of Biginelli adducts. [a] Mr. Scheme 1. Biginelli reaction. ChemistrySelect Reviews Figure 1. Structure of ionic liquids. Scheme 2. Synthesis of DHPMS by [C 3 SO 3 HDoim]HSO 4. Scheme 3. Synthesis of 7 by L-proline nitrate.ChemistrySelect Reviews

Regionally available bentonite was modified by using heteropolyacid 12‐tungstosilicic acid H4[W12SiO40] (TSA). The prepared 10–30 % TSA/bent catalysts were characterized by XRD, FTIR, FeSEM and EDS. The catalytic activity of all three samples was studied on classical Biginelli reaction. Among all, 30 % TSA/bent displayed high catalytic activity and reusability. The effect of solvent was also undertaken to find the best media for the reaction. This protocol was extended to various aldehydes for the synthesis of different dihydropyrimidones (DHPMs) in high yields in ethanol.

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Fe(III) immobilized over natural bentonite (bent) using the impregnation method. Prepared catalysts were well characterized by XRD, FT-IR and FeSEM. The catalytic activity of three catalysts 10, 20 and 30 % Fe(III)/bent evaluated for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones known as Biginelli reaction. The catalyst 30 % Fe(III)/bent exhibited a high yield of the product towards the synthesis of a variety of dihydropyrimidones (DHPMs). The high yield of dihydropyrimidone (DHPM) was obtained in model reaction in ethanol, acetonitrile, DMF and solvent-free condition. The reusability test indicated that 6 % of yield of product decreased after 5 th cycle. Highlights * 10, 20 and 30 % Fe(III) were supported over bentonite clay. The catalysts are well characterized by (XRD), FT-IR, FeSEM and EDS. All charactization method showed that Fe supported over bentonite. * The used catalysts were screened for Biginelli reaction for synthesis dihydropyrimidones. * 30 % Fe(III)/bent exhibited high yield of product towards model Biginelli reaction between benzaldehyde, ethylacetoacetate and urea in ethanol. * 30 % Fe(III)/bent exhibited high yield of product in CH 3 CN, DMF and solvent free-condition. * The catalyst 30 % Fe(III)/bent applied for synthesis of variety of dihydropyrimodone in good yield in CH 3 CN. * Reusability studies show that no great decline in activity after 5 th cycle.