Stereoselective preparation of 1,2,4-oxadiazole derivatives substituted by pentafluorophenyl by 1,3-dipolar cycloaddition reaction

1,3-Dipolar cycloaddition reactions of chiral imines obtained from optically active amino acids with nitrile oxides afforded 1,2,4-oxadiazole derivatives in moderate to good yields with good stereoselectivity. Investigation on the effect of bases suggested that triethylamine was prone to afford better stereoselectivity, while NaHCO 3 was prone to increase the reaction rates and yields.