A NEW CATALYTIC ACTIVITY OF ANTIMONY(III) CHLORIDE IN PALLADIUM(0)-CATALYZED CONJUGATE ADDITION OF AROMATICS TO ALPHA,BETA-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 alpha,beta-unsaturated ketones and aldehydes with sodium tetraphenylborate and arylboronic acids in acetic acid at 25 degrees C. Several other metal chlorides such as AlCl3, SnCl4, AsCl3, TiCl4, FeCl3, MoCl5, 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.