Indium-catalyzed reduction of allyl bromide with gallium or aluminum. Formation of allylgallium and allylaluminum sesquibromides.

[reaction: see text] Fast transmetalation of an allyl group from indium to gallium enables the assembly of a catalytic cycle of indium, which accelerates the formation of allylgallium sesquibromide. A solution of allylaluminum sesquibromide in THF is also prepared from allyl bromide and aluminum metal under indium catalysis.