Palladacycles as Efficient Catalysts for Aryl Coupling Reactions

The catalytic CC coupling of chloroarenes by both the Heck and the Suzuki reactions has been achieved for the first time with new palladacycles of type 1, in which R can be, for instance, o-tolyl or mesityl. They are an order of magnitude more active than conventional catalysts and, moreover, thermally considerably more robust. But above all, the cleavage of the PC bond and the deposition of palladium is not observed. Analogous reactions with bromoarenes can also be catalyzed to advantage with 1. The Heck reaction of haloarenes with vinyl derivatives (e.g., n-butyl acryiate) gives (E)-styrene derivatives in one step. In the Suzuki reaction the haloarenes are converted into biphenyl derivatives with phenylbornic acid, also in one step.