Characterization of 2-aryl-1,3,4-oxadiazoles by 15N and 13C NMR spectroscopy

N-15 NMR chemical shifts of 2-aryl-1,3,4-oxadiazoles were assigned on the basis of the H-1-N-15 HMBC experiment. Chemical shifts of the nitrogen and carbon atoms in the oxadiazole ring correlate with the Hammett sigma-constants of substituents in the aryl ring (r(2)greater than or equal to0.966 for N atoms). N-15 NMR data are a suitable and sensitive means for characterizing long-range electronic substituent effects. Additionally, C-13 NMR data for these compounds are presented. Copyright (C) 2003 John Wiley Sons, Ltd.