NMR-STUDY OF IMINOPHOSPHINE OLIGOMERS BY P-31,N-15 AND P-31,C-13 HETERONUCLEAR SHIFT CORRELATION

2D P-31, N-15 heteronuclear shift correlation, based on a non-refocuse d INEPT pulse sequence with N-15 detection, was applied to a N-15 NMR Study of the azadiphosphiridines 1-5 which are formed by [2 + 1] cyclo addition of iminophosphines, RP=NR'. The pulse sequence used allowed c onsistent assignment of both the P-31 and N-15 NMR spectra in one expe riment; by a slight modification, also the signs of numerous P-31-N-15 coupling constants across one or two bonds could be determined. Compa rison of the data with those of the azatriphosphetidine 6 (obtained fr om 1D H-1,N-15 and P-31,N-15 INEPT spectral showed the influence of th e ring size and conformational effects on the NMR parameters. P-31,C-1 3 shift-correlated 2D spectra were further used to measure (including sign determination) and assign P-31-C-13 coupling constants across one to three bonds in 1-5. Based on the analysis of the coupling informat ion and the known conformation of 4a, the relative stereochemistry of the diastereomers 4a and b could be derived; further, the comparison o f the P-31-C-13 coupling data of 1-3 with those of the 4a and b allowe d the conformations of these derivatives, which were previously unknow n, to be determined. The derived information of the constitution and s tereochemistry of 1-5 gives insight into mechanistic details of the im inophosphine [2 + 1] cycloaddition.