Linear free energy relationships of 13C NMR chemical shifts in 4-substituted phenyl-4,5-dihydrobenzo[f][1,4]oxazepin-3(2H)-ones(thiones)

Linear free energy relationships (LFER) were applied to the 13C NMR chemical shifts in 4-substituted phenyl-4,5-dihydrobenzo[f][1,4]oxazepin-3(2H)-ones(thiones). The correlation analysis for the substituent-induced chemical shifts (SCS) with inductive and resonance parameters (σ, F and R) were carried out by using SSP (single substituent parameter) and DSP (dual substituent parameter). The presented calculation accounts satisfactorily for the polar and resonance substituent effects operating at benzoxazepine carbon atoms. Negative ρ values were found for several correlations (reverse substituent effect). For a better understanding of the results, density functional theory (DFT) calculations were performed to determine the preferred geometry and to calculate the theoretical 13C NMR chemical shifts.