A series of quinoline based 1,3,4-oxadiazole derivatives 8a-l were synthesized by chloro-amine coupling reaction approach with different catalyst and solvents. The substituted 1,3,4-oxadiazole intermediates 7a-c were obtained from 2-sustituted-N-phenylhydrazinecarbothioamide 6a-c by cyclization with different cyclizing reagents like mercuric acetate, lead dioxide, iodobenzenediacetate (IBD) and aqueous sodium hydroxide with iodine in aqueous potassium iodide to isolate the most effective reaction condition by using iodobenzenediacetate as extremely good catalyst. The structure of the title compounds were confirmed by FT-IR, 1 H NMR, 13 C NMR and mass spectrometry. The synthesized molecules were evaluated for their antibacterial, antifungal, antituberculosis and antimalarial activities. The brine shrimp bioassay was carried out to study the in vitro cytotoxic properties for the highly active compounds of in vitro biological evaluation. antifungal 34 . Quinoline scaffolds have been selected due to their diverse therapeutic and pharmacological properties, such as antitumor, antiatherosclerotic, vasodilator, geroprotective, bronchodilator and hepatoprotective activity 35 .
212 5 A one-pot three-component approach for the synthesis of 2-(piperidin-1-yl) quinoline based 1,2,4triazolo[1,5-a]quinoline derivatives (4a-l) has been described by the reaction of aldehyde (1a-f), methyl 2-cyanoacetate (2) and enaminones (3a-b). Regioselectivity of reaction attained by different catalyst and higher regioselectivity is achieved by L -proline. This new procedure provides an efficient method to 10 construct fused tricyclic heterocycles containing 1,2,4-triazole analogues. In this regards, we have using least amount of amphoteric catalyst like L -proline, ammonium acetate and mixture of pyrolidine with acetic acid to obtain 1,4-dihydroquinoline derivative 5a as a by product, where as mild reaction condition, high yield (75-85%) and higher regioselectivity toward desired products 4a-l are the salient features of this protocol. The structures of the title compounds were confirmed by FT-IR, 1 H NMR, 13 C NMR and 15 mass spectrometry. 65 a]quinoline. However, practical and general approaches to this type of fused quinoline are rare in the literature. Herein we report a much improved and new synthesis of 1,2,4-triazolo[1,5a]quinoline over a polyhydroquinoline using aldehyde, methyl 2cyanoacetate and enaminones in the presence of L -proline as a 70 catalyst and ethanol as solvent.(Scheme 2).We began our studies by screening different catalysts for their
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