Palladacycles as Structurally Defined Catalysts for the Heck Olefination of Chloro‐ and Bromoarenes

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. (Figure Presented.)