13C NMR substituent-induced chemical shifts in 4-(substituted phenyl)-3-phenyl-1,2,4-oxadiazol-5(4H)-ones (thiones)

In the present, study mostly novel ten 4-(substituted phenyl)-3-phenyl-1,2,4-oxadiazol-5(4H)-ones and ten 4-(substituted phenyl)-3-phenyl-1,2,4-oxadiazol-5(4H)-thiones were synthesized. These oxadiazole derivatives were characterized by IR, H-1 NMR, C-13 NMR and elemental analyses. Their C-13 NMR spectra were measured in Deuterochloroform (CDCl3). The correlation analysis for the substituent-induced chemical shift (SCS) with Hammett substituent constants (sigma), Brown Okamoto substituent constants (sigma(+), sigma(-)), inductive substituent constants (sigma(1)) and different of resonance substituent constants (sigma(R), sigma(o)(R)) were performed using SSP (single substituent parameter), DSP (dual substituent parameter) and DSP-NLR (dual substituent parameter-non-linear resonance) methods, as well as single and multiple regression analysis. Negative rho values were found for all correlations (reverse substituent effect). The results of all statistical analyses, C-13 NMR chemical shift of C=N, C=O and C=S carbon of oxadiazole rings have shown satisfactory correlation. (C) 2015 Elsevier B.V. All rights reserved.