A New Catalytic Activity of Antimony(III) Chloride in Palladium(0)-Catalyzed Conjugate Addition of Aromatics to αpha;,β-Unsaturated Ketones and Aldehydes with Sodium Tetraphenylborate and Arylboronic Acids

A remarkable catalytic effect of antimony(III) chloride is disclosed in palladium(0)-catalyzed conjugate addition of aromatics to αpha;,β-unsaturated ketones and aldehydes with sodium tetraphenylborate and arylboronic acids in acetic acid at 25 °C. Several other metal chlorides such as AICI₃, SnCl₄, AsCl₃, TiCl₄, FeCl₃, M0CI₅, and CeCl₃ are also effective in some cases, but SbCl₃ is the salt of choice. Two key steps are proposed for this reaction: one is the oxidative addition of a C-B bond to Pd(0) forming an arylpalladium species, and the other is the formation of an antimony enolate derived from the initial coordination of SbCl₃ to the carbonyl oxygen of an organopalladium intermediate.