Iridium-Catalyzed Addition of Aroyl Chlorides and Aliphatic Acid Chlorides to Terminal Alkynes

Iridium complexes show high catalytic activity in intermolecular additions of acid chlorides to terminal alkynes to afford valuable (<i>Z</i>)-β-chloro-α,β-unsaturated ketones. Ligands in the catalytic system play a crucial role in this reaction. An <i>N</i>-heterocyclic carbene (NHC) is an efficient ligand for the addition of aroyl chlorides, while dicyclohexyl­(2-methylphenyl)­phosphine (PCy<sub>2</sub>(<i>o</i>-Tol)) is indispensable for the reaction of aliphatic acid chlorides. The addition reactions proceed regio- and stereoselectively with suppression of decarbonylation and β-hydrogen elimination, which have been two major intrinsic problems in transition-metal-catalyzed reactions. Stoichiometric reactions of active iridium catalysts with aroyl chlorides and aliphatic acid chlorides are carried out to gain insights into the reaction mechanisms.