Indium(III)-catalyzed Coupling between Alkynes and Aldehydes to α,β-Unsaturated Ketones

The combined use of a catalytic amount of InX3 (X = OTf and NTf2) and 1-butanol was found to be effective in formal alkyne-aldehyde metathesis. With this catalytic system, aromatic alkynes reacted with aromatic aldehydes to give chalcones in moderate to good yields. Alkynals were efficiently converted into 5- to 7-membered cyclic compounds by intramolecular alkyne-aldehyde coupling.