Regioselectively [(NO2)-N-15]-labeled N-methoxypicramide and DPPH preparedby using crown ether and solid sodium [N-15]nitrite

The present paper reports the regioselective [(NO2)-N-15]-labeling of N-met hoxy-2,4,6-trinitroaniline and 2,2-diphenyl-1-picrylhydrazine (reduced DPPH ). Starting from N-methoxy-2, 6-dinitroaniline, or N-methoxy-2,4-dinitroani line, nitration in methylene chloride with solid sodium [N-15]nitrite and 1 5-crown-5-ether afforded N-methoxy-2,6-dinitro-4-[N-15]nitroaniline and N-m ethoxy-2,4-dinitro-6-[N-15]nitroaniline respectively. The same compounds co uld be prepared in higher purity by nitrodecarboxylation (ipso-substitution ) under the same conditions starting from N-methoxy-4-carboxy-2, 6-dinitroa niline (4-methoxyamino-3, 5-dinitrobenzoic acid) and N-methoxy-2-carboxy-4, 6-dinitroaniline (2-methoxyamino-3,5-dinitrobenzoic acid), Similarly, ipso -substitution of 2,2-diphenyl-1-(4-carboxy-2,6-dinitrophenyl)-hydrazine aff orded, under the same reaction conditions, 2,2-diphenyl-1-(2,6-dinitro-4-[N -15]nitrophenyl)-hydrazine. By H-1-NMR and C-13-NMR it was also observed th at under these reaction conditions a (NO2)-N-14 group can be replaced by a (NO2)-N-15 group.