NMR-STUDIES ON AMINATED DINITROBENZOFUROXAN AND DINITROBENZOFURAZAN DERIVATIVES

The C-13-n.m.r. chemical shifts of sigma-N-C-bonded Meisenheimer complexes 3, 5 and their corresponding aminated dinitrobenzofurazans 4 and dinitrobenzofuroxans 6 were determined. The chemical shifts are discussed as a function of electronic substituent effects. The assignment was performed by means of H-1-C-13 coupling constants and by comparison with che C-13-chemical shifts of appropriate model compounds. The C-13-n.m.r. spectra of Meisenheimer tomplexes 3 reveal doubling of signals, indicating a hindered rotation at the N-CHO bond.