Abstract
We report here an efficient and green method for Biginelli condensation reaction of aldehydes, β-ketoesters and urea or thiourea catalyzed by Brønsted acidic ionic liquid [Btto][p-TSA] under solvent-free conditions. Compared to the classical Biginelli reaction conditions, the present method has the advantages of giving good yields, short reaction times, near room temperature conditions and the avoidance of the use of organic solvents and metal catalyst.
Highlights
Over the years, dihydropyrimidinones (DHPMs) and their derivatives have displayed a captivating assortment in natural, synthetic, pharmacological, therapeutic and bioorganic chemistry mainly due to their wide range of biological activities [1,2,3], and they are being studied because of their activities as Molecules 2015, 20 calcium channel blockers, antihypertensive agents, alpha-la-antagonists and neuropeptide Y(NPY)antagonists [4,5]
The most simple and straightforward procedure for the synthesis of DHPMs was first reported by the Italian chemist Pietro Biginelli in 1893, it involves a three-component one-pot condensation of benzaldehyde, ethyl acetoacetate and urea under strongly acidic conditions [10]
Several protocols for the synthesis of DHPMs have been developed to improve and modify this reaction by means of microwave irradiation [11,12], ultrasound irradiation [13], ionic liquids [14,15,16], and different types of acidic, base, metal oxide, nanoparticle, enzyme, phase transfer catalysts such as lanthanide triflate [17], H3BO3 [18], VCl3 [19], Sr(OTf)2 [20], PPh3 [21], Indium(III) halides [22], nanomagnetic-supported sulfonic acid [23], Iron(III) tosylate [24], Bis[(L)prolinato-N,O]Zn-water [25], 1-glycyl-3-methyl imidazolium chloride copper(II) Complex [26], KAl(SO4)2·12H2O supported on silica [27], FeCl3-supported nanopore silica [28], SiO2-CuCl2 [29], metal oxide-MWCNTs [30,31,32], Fe3O3 and boehmite nanoparticle [33,34], nanosilica-supported tin(II)
Summary
Dihydropyrimidinones (DHPMs) and their derivatives have displayed a captivating assortment in natural, synthetic, pharmacological, therapeutic and bioorganic chemistry mainly due to their wide range of biological activities [1,2,3], and they are being studied because of their activities as Molecules 2015, 20 calcium channel blockers, antihypertensive agents, alpha-la-antagonists and neuropeptide Y(NPY). The most simple and straightforward procedure for the synthesis of DHPMs was first reported by the Italian chemist Pietro Biginelli in 1893, it involves a three-component one-pot condensation of benzaldehyde, ethyl acetoacetate and urea under strongly acidic conditions [10]. This reaction usually requires harsh conditions, long reaction times and affords low yields, when substituted aromatic and aliphatic aldehydes are employed, which impede their applications.
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