Iodonium derivatives of heterocyclic compounds

Reaction of indole with phenyl iodosoacetate in alkaline media leads to the unstable Β-phenyliodonioindole betaine, the more stable tosylate and fluoborate of which were used for the introduction of a pyridine, quinoline, and isoquinoline molecule into the Β-position of indole to give the corresponding tosylates and fluoborates of Β-(N-pyridinio)-, Β-(N-quinolinio)-, and Β-(N-isoquinolinio)indole. Intramolecular charge transfer from the donor indole system to the acceptor onium systems is detected from the UV spectral data. The acidity constants of a number of Β-onium derivatives of indole were determined by spectrophotometry.