Iridium-catalyzed addition of aroyl chlorides and aliphatic acid chlorides to terminal alkynes.

Tomohiro Iwai, Tetsuaki Fujihara, Jun Terao, Yasushi Tsuji

Index: J. Am. Chem. Soc. 2nd ed., 134 , 1268-1274, (2012)

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Abstract

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 (PCy(2)(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.© 2011 American Chemical Society