Indium-Mediated Cyclization Chemistry

During our investigation of the indium-mediated cyclization of allyl bromides onto alkynes, we discovered an efficient cyclization reaction that proceeds with transfer of a bromine atom when halogenated solvents were used. For some substrates, this reaction pulled chlorine atom from the solvent. This isomerization reaction proceeds via an ionic mechanism of halogen activation to do a Friedel-Crafts type of cyclization and not a radical pathway as we originally thought.