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
(Z)-β-chloro-α,β-unsaturated ketones.
Ligands in the catalytic system play a crucial role in this reaction.
An N-heterocyclic carbene (NHC) is an efficient ligand
for the addition of aroyl chlorides, while dicyclohexyl­(2-methylphenyl)­phosphine
(PCy2(o-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.