13C NMR spectra of tricyclic diaziridines and their data-base forecasts

The 13C NMR data for tricyclic and bicyclic diaziridines with condensed five- and six-membered rings are interpreted and compared with the forecast of the C13-NMR/IR data-base (successor: SPECINFO data-base). There are large differences in chemical shifts and large deviations in the forecasts. Bond angles from semi-empirical AM1 calculations with geometry optimization correlate with the observed shifts. Similar behaviour is found for some known bicyclic diaziridines, and this is also discussed together with some known 13C shift variations in other diaziridines and bicyclic hydrocarbons. It is suggested that the widely used data-base should include subset search facilities in order to minimize the risk of misassignments. This would allow specific effects, such as those of bond angles in cyclic compounds, to be taken into consideration.