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

Abstract 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.