Interpretation of substituent-induced 13C NMR chemical shifts of oxindoles

Based on the 13C NMR chemical shifts of more than 300 oxindole derivatives, substituent-induced chemical shifts have been calculated for this family of compounds. These substituent effects have been compared to those of monosubstituted benzenes and the correlation with the Hammett σ values and dual substituent parameters has also been tested. By means of these validated substituent effects, the 13C NMR chemical shifts of the oxindole skeleton containing various substituents can be accurately predicted.