Synthesis and substituent effect study on 13C NMR chemical shifts of 4-(substitue-phenyl)-6-methyl-3-phenyl-4H-1,2,4-oxadiazin-5(6H)-one

Abstract

The twelve novel 4-(substituted-phenyl)-6-methyl-3-phenyl-4H-1,2,4-oxadiazin-5(6H)-one derivatives were synthesized by the reactions of N-Substituted-phenyl-benzamide oximes with 2-bromopropionyl chloride. The synthesized 1,2,4-oxadiazin-5-one derivatives were characterized by their physical constants and IR, 1H NMR, 13C NMR and LC/TOF-MS analyses data. The experimental 13C NMR chemical shifts (ppm) (SSC) of the C=O, C=N, CH and CH3 carbons of these 1,2,4-oxadiazin-5-one derivatives were correlated with the various Hammett substitution constants and Swain-Lupton parameters, using single (SSP) and multi-linear (DSP) regression analysis. Negative ρI and ρR values were found for correlations of C=O, C=N and CH3 carbons (reverse substituent effect). For the other carbon (CH), positive ρI (normal substitution effect) and negative ρR (reverse substitution effect) values were calculated by DSP regression analysis. As a result of DSP regression analysis, the 13C NMR chemical shift of the C=O, C=N and CH carbons of the oxadiazine ring showed a satisfactory correlation (r > 0.90), while excellent correlation was observed at the CH3 carbon (r = 0.99). The 13C NMR chemical shift values of the C=O, C=N, CH and CH3 carbons of the p-Br-substituted 1,2,4-oxadiazin-5-one derivative were estimated using the equations obtained by the DSP regression analysis. These predicted 13C NMR chemical shifts were compared with experimental 13C NMR chemical shifts for 4-(4-bromophenyl)-6-methyl-3-phenyl-4H-1,2,4-oxadiazine-5(6H)-one derivatives.