| Abstract
| - 2-Alkoxycarbonylazolium N-aminides are interesting species, as they have the potential to act asefficient 1,4-dipole equivalents when they react with heterocumulenes, such as iso(thio)cyanatesand carbodiimides. These reactions give heterobetaines containing the imidazo[2,1-f][1,2,4]triazinium system, in a formal [4 + 2] cyclocondensation process. These N-aminides, however, canalso behave as 1,3-dipoles when they react with isocyanates to afford a cycloadduct that, dependingon the position of alkoxycarbonyl group, can undergo a reversion process or a ring expansion to themore stable heterobetaine system.
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