Unprecedented Rearrangement of 2-(2-Aminoethyl)-1-aryl-3,4-dihydropyrazino[1,2-<i>b</i>]indazole-2-ium 6-oxides to 2,3-Dihydro-1<i>H</i>-imidazo[1,2-<i>b</i>]indazoles

Easily accessible 2-(2-aminoethyl)-1-aryl-3,4-dihydropyrazino[1,2-b]indazole-2-ium 6-oxides rearranged to 2,3-dihydro-1H-imidazo[1,2-b]indazoles under mild conditions. The rearrangement appeared to be general, tolerated a wide range of functional groups, and provided access to an as yet unexplored class of heterocycles. Herein we report the characterization of these heterocycles.