Superacid-Promoted Synthesis of Imidazole-Containing Spirocycles

A series of imidazole-containing fluorenyl spirocycles have been prepared from 9-fluorenol derivatives. Highly acidic media and superacid media are shown to promote spirocyclization to this new class of spirocycles. A mechanism is proposed involving fluorenyl cationic species, including dicationic ions. Electrochemical and optical experiments were conducted for the calculation of frontier molecular orbital energy levels. Fluorescence spectroscopy showed that select conjugated fluorophores were intensely emissive in the near-UV visible (blue-purple) spectrum range.