Indium(III) bromide catalyzed one-pot synthesis of trichloromethylated tetrahydropyrimidinones

A Five-Component Biginelli-Diels-Alder Cascade Reaction

A new multi-component condensation was discovered during the reaction of a urea, β-keto ester, and formaldehyde. In the presence of catalytic indium bromide, a Biginelli dihydropyrimidinone intermediate was further converted to a five-component condensation product through a formal hetero Diels-Alder reaction. The product structure was confirmed by NMR and NOE analysis, and the proposed stepwise mechanism was supported by the reaction of the Biginelli intermediate with ethyl 2-methylene-3-oxobutanoate.

A new paradigm for designing ring construction strategies for green organic synthesis: implications for the discovery of multicomponent reactions to build molecules containing a single ring

A new way of developing novel synthesis strategies for the construction of monocyclic rings found in organic molecules is presented. The method is based on the visual application of integer partitioning to chemical structures. Two problems are addressed: (1) the determination of the total number of possible ways to construct a given ring by 2-, 3-, and 4-component couplings; and (2) the systematic enumeration of those possibilities. The results of the method are illustrated using cyclohexanone, pyrazole, and the Biginelli adduct as target ring systems with a view to discover new and greener strategies for their construction using multicomponent reactions. The application of the method is also extended to various heterocycles found in many natural products and pharmaceuticals.

Lithium-acetate-mediated Biginelli one-pot multicomponent synthesis under solvent-free conditions and cytotoxic activity against the human lung cancer cell line A549 and breast cancer cell line MCF7

Various Biginelli compounds (dihydropyrimidinones) have been synthesized efficiently and in high yields under mild, solvent-free, and eco-friendly conditions in a one-pot reaction of 1,3-dicarbonyl compounds, aldehydes, and urea/thiourea/acetyl thiourea using lithium-acetate as a novel catalyst without the addition of any proton source. Comparative catalytic efficiency of lithium-acetate and polyphosphoric acid to catalyze Biginelli condensation is also studied under neat conditions. The reaction is carried out in the absence of any solvent and represents an improvement of the classical Biginelli protocol and an advantage in comparison with FeCl₃·6H₂O, NiCl₂·6H₂O and CoCl₂·6H₂O that were used with HCl as a cocatalyst. Compared to classical Biginelli reaction conditions, the present method has advantages of good yields, short reaction times, and experimental simplicity. The obtained products have been identified by spectral (¹H NMR and IR) data and their melting points. The prepared compounds are evaluated for anticancer activity against two human cancer cell lines (lung cancer cell line A549 and breast cancer cell line MCF7).

Antioxidant capacity and environmentally friendly synthesis of dihydropyrimidin-(2H)-ones promoted by naturally occurring organic acids

The Biginelli reaction is a multicomponent reaction involving the condensation between an aldehyde, a β-ketoester, and urea or thiourea, in the presence of an acid catalyst, producing dihydropyrimidinones (DHPMs). Owing to their important pharmacological properties, the DHPMs have been studied by many authors. However, most of the methodologies used for the synthesis of these compounds require drastic reaction conditions. In the current study, we report an efficient and clean procedure for preparing DHPMs by the use of citric acid or tartaric acid as a promoter of the Biginelli synthesis in ethanol as solvent. In addition, we have evaluated the antioxidant capacity of the compounds synthesized by the 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay and the thiobarbituric acid-reactive species test. Two compounds presented antioxidant activity and also reduced lipid peroxidation at concentrations of 200 and 300 µM. In summary, we report an environmentally friendly procedure for the preparation of DHPMs and demonstrate the antioxidant capacity of some of the compounds.