It is shown that both tribromoisocyanuric acid (TBCA) and trichloroisocyanuric acid (TCCA) are excellent reagents for direct halogenation of electron‐rich aromatics under solvent‐free, ball‐milling conditions. The results are remarkable in light of the fact that chlorination of aromatics without any acid catalyst is heretofore unknown. The procedure is operationally simple, and the reactions occur within a few hours, affording high yields of halogenated products. Similarly, crystalline β‐keto dicarbonyl compounds are shown to undergo direct α,α‐dihalogenation with TBCA and TCCA with ball milling. Whereas monoketones are found to be unreactive with TBCA/TCCA, addition of 25 mol‐% of p‐toluenesulfonic acid as a solid catalyst catalyzes the reaction, leading to the formation of α‐chloro/bromo ketones in very good isolated yields. The fact that each of the reagents, in principle, serves as a source of three halogen atoms should render solvent‐free halogenation of aromatics and carbonyl compounds with TBCA/TCCA an invaluable synthetic protocol.
New coumarin‐benzimidazole hybrids (3a–f) have been synthesized from 4‐formylcoumarins and a series of N‐sulphonation (4 a‐f) and N‐methylation (5 a‐f) compounds were obtained from compounds (3a–f). All the synthesized compounds have exhibited good antimicrobial activity. Docking studies provide valuable insights to potential binding modes of inhibitors. Anti cancer activity of compound 4 a and 4 c have shown excellent activity against HeLa cell line. Whereas compound 4 a and 4 d exhibited higher activity against HT 29 cell lines. We calculated the LC50, TGI and GI50 which show < 10 mg/mL. The synthesized compounds were characterized by IR, NMR, Mass spectral analysis and few of them by single X‐ray crystallography analysis.
α-Chloroketones - obtained by the atom-economical chlorination of ketones with trichloroisocyanuric acid (TCCA) in the presence of p-TSA under ball-milling conditions - were set up for a sequential base-mediated condensation reaction with thiourea/thiosemicarbazides, o-phenylenediamine and salicylaldehyde to afford 2-aminothiazoles, 2-hydrazinylthiazoles, quinoxalines and benzoylbenzofurans, respectively, in respectable yields. The viability of one-pot sequential acid- and base-mediated reactions in the solid state under ball-milling conditions is thus demonstrated.
Abstract. Different substituted diesters of thiazolopyrimidine were prepared by the treatment of 3,4 dihydropyrimidine2-thione with α-haloesters using ethanol under reflux condition affording 71-85% yield. IR, 1 HNMR, 13 CNMR and elemental analyses were used for the characterization of these compounds. The crystal and molecular structure of one of the product, 5-phenyl-3,7-dimethyl-5H-thiazolo[3,2-a]pyrimidine-2,6-dicarboxylic acid diethyl ester (3e) was verified by single crystal X-ray diffraction method. The antimicrobial activity was evaluated against four bacterial strains and one fungal species. Few of the derivatives exhibited antibacterial and antifungal activities.
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