Substituent effect study on the experimental 13C NMR chemical shifts of 3-(substituted phenyl)-3a,4,8,8a-tetrahydro-1,3-dioxepino[5,6-d] [1,2] isoxazoles

Abstract

Novel heterocyclic derivatives containing isoxazole ring were synthesized by the 1,3-dipolar cycloaddition reaction of substituted nitrile oxides with cis-4,7-dihydro-1,3-dioxepin in the present study. These 3-(substituted phenyl)-3a,4,8,8a-tetrahydro-1,3-dioxepino[5,6-d] [1,2] isoxazole derivatives were characterized by their physical constants and IR, 1H NMR, 13C NMR and HRMS data. 13C NMR spectra of studied molecules were measured in Deuterochloroform (CDCl3). The correlation analysis for the substituent-induced experimental 13C NMR chemical shifts (δ, ppm) (SSC) of C=N, C4, C5, C7, C9 and C10 carbons of these isoxazole derivatives have been correlated with various Hammett substituent constants, and Swain-Lupton parameters using single (SSP) and multi-linear (DSP) regression analysis. Negative ρ values were found for correlations of C=N, C4 and C5 carbons. The other carbons were found to have positive ρ values for the electronic effect of substituent on 13C NMR chemical shifts.