Syntheses and<sup>15</sup>N NMR Spectra of Iminodiaziridines - Ring-Expansions of 1-Aryl-3-iminodiaziridines to 1<i>H</i>- and 3a<i>H</i>-Benzimidazoles, 2<i>H</i>-Indazoles, and 5<i>H</i>-Dibenzo[<i>d</i>,<i>f</i>][1,3]diazepines
3-dihydro-3aH-benzimidazoles. Otherwise, 2-amino-1H-benzimidazoles and strongly fluorescent 3-amino-2H-indazoles, originating from rearrangements of the elusive 1-aryl-3-iminodiaziridines, predominate. N′,N″-Diaryl-N-hydroxyguanidine O-sulfonic acids give only rearranged products: a 2-amino-1H-benzimidazole and a 6-amino-5H-dibenzo[d,f][1.3]diazepine if aryl = phenyl, or a 2-imino-2,3-dihydro-3aH-benzimidazole