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Eco-friendly approach to synthesis of coumarinyl 1, 2, 4-triazoles

1, 2, 4-triazoles, heterocyclic compounds with a wide range of biological activities such as antibacterial, antifungal, antitumor, anticolvulsant, antiinflammatory and antimicrobial, exists in two tautomeric forms, 1H and 4H. Until recently, these heterocycles are usually prepared from 1, 2, 4-oxadiazoles in reaction with hydrazine, 1, 3, 4-oxadiazoles and hydrazides or thiosemicarbazides in basic conditions or triethylamine. A model reaction between 2-((4-methyl-2-oxo-2H-chromen-7-yl)oxy)acetohydrazide and phenyl isothiocyanate was carried out on two different temperatures (40 °C and 80 °C) in 14 choline chloride based deep eutectic solvents (DESs). DES is a mixture of a salt, usually chloline chloride wich is hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD) such as alcohols, sugars, amides and carboxyl acids and mostly exist as liquid at or below 100 °C. Pure thiosemicarbazide was formed in choline chloride:malonic acid (1:1), choline chloride:malic acid (1:1) and DESs with different alcohols as HBDs. The best conversion to 1, 2, 4-triazole derivatives was obtained in choline chloride:urea (1:2) at 80 °C, so this DES was used for next synthesis of 1, 2, 4-triazoles with various isothiocyanates and hydrazides.

1, 2, 4-triazole, thiosemicarbazide, isothiocyanate, deep eutectic solvent, green synthesis

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