P. Sanjeeva, B. Rao, V. Prasad
Aug 25, 2021
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Journal
Research Journal of Chemistry and Environment
Abstract
The six benzofuran-oxadiazole derivatives (4a-d) and (5a-b) have been designed, synthesized, characterized and evaluated for antimicrobial activity. The key synthetic intermediate 5-bromo-N'-hydroxybenzofuran -2-carboxamidine (3) was prepared from 5-bromobenzofuran-2-carboxylic acid (1) in two consecutive steps involving reaction with NaN3, in presence of TEA, Xtalfluor-E, PPh3 in dry DCM at 0oC followed by the treatment of resulting carbonitrile (2) with hydroxylamine hydrochloride in presence of sodium methoxide under reflux in aqueous ethanol. Reaction of carboxamidine (3) with different aryl esters in presence of K2CO3 under reflux conditions in toluene afforded 3-(5-bromobenzofuran-2-yl)-5-substituted phenyl-1,2,4-oxadiazoles (4a-d) while the refluxion of a solution of carboxamidine (3) in dichloromethane with chloro/bromo acetyl chloride in presence of TEA and a catalytic amount of HBTU furnished 3-(5-bromobenzofuran-2-yl)-5-(chloromethyl)-1,2,4-oxadia zole (5a) and 3-(5-bromobenzofuran-2-yl)-5-(bromomethyl)-1,2,4-oxadiazole (5b).