Lewis Acid-Mediated Cyclization of Allenyl Aryl Ketones.

The cyclization of a series of nonheterocyclic allenyl aryl ketones was examined using boron trifluoride etherate and indium triflate to mediate the reaction. Yields with BF were low in most instances due mainly to competitive destruction of the substrates. With In(OTf), there was less decomposition, and the yields of the cyclized product were much higher, but only for substrates with electron-donating substituents.