1,3-Dipolar Cycloaddition Reaction of Nitrile Oxide to Thiocyanates: An Efficient and Eco-Friendly Synthesis of N-Aryl-2-((3-aryl-1,2,4-oxadiazol-5-yl)thio)acetamides

An efficient and eco-friendly procedure was developed for the synthesis of N-aryl-2-((3-aryl-1,2,4-oxadiazol-5-yl)thio)acetamides from N-aryl-2-thiocyanatoacetamides and substituted N-hydroxybenzimidoyl chlorides that were prepared easily from the commercially available anilines and aryl aldehydes, respectively. The N-aryl-2-thiocyanatoacetamide acts as a dipolarophile while the nitrile oxide formed in situ from substituted N-hydroxybenzimidoyl chloride acts as the nucleophilic partner in a 1,3-dipolar cycloaddition reaction mediated by triethylamine base in ethanol medium. The procedure affords excellent yields of desired products containing electron-withdrawing and electron-donating groups on the aromatic rings, in short reaction time with ease of operation. The procedure for the synthesis of scaffolds that are potentially valuable for their biological properties also offers the possibility of scale-up to higher quantities.