Comparison of palladium carbene and palladium phosphine catalysts for catalytic coupling reactions of aryl halides

Palladium-catalyzed C-C and C-N bond forming reactions of aryl halides continue to be a major focus in catalysis research for the fine chemical industry. Still there exists a significant need for the development of more active and productive palladium catalysts. Although an increasing number of new catalysts is reported, it is often difficult to compare them. Here, we present a more detailed comparison of the catalytic performance of different monocarbenepalladium(0) complexes and various so-called in situ palladium phosphine and carbene catalysts in Suzuki, Kumada, and Buchwald-Hartwig animation reactions. Depending on the type of coupling reaction good to excellent yields of the desired products are obtained in the presence of both carbene- and phosphine-based catalysts. In general, phosphine-based catalysts appear to be more efficient for amination and Suzuki reactions of aryl chlorides. On the other hand, the carbene-based palladium catalysts work well in Kumada couplings of various aryl chlorides. (C) 2004 Elsevier B.V. All rights reserved.