Palladium Catalyzed Reactions in Ionic Liquids

Palladium Catalyzed Reactions in Ionic Liquids TOM WELTON and PAUL J. SMITH Department of Chemistry, Imperial College of Science, Technology and Medicine, South Kensington, London, SW7 2AY, UK

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Introduction . . . . . . . . . . . . . . . . . . . . . . What are Ionic Liquids? . . . . . . . . . . . . . . . . A. Characteristics of Ionic Liquids . . . . . . . . . B. Quantifying Solvent Properties . . . . . . . . . . Introduction to Palladium Catalysis in Ionic Liquids Heck Reactions . . . . . . . . . . . . . . . . . . . . A. Thermal Heck Reactions . . . . . . . . . . . . . B. Ultrasound Assisted Heck Reactions . . . . . . . C. Microwave Assisted Heck Reactions . . . . . . . D. Supported Heterogeneous Palladium Systems . . Allylation/Trost–Tsujii Reactions . . . . . . . . . . . Cross-coupling Reactions . . . . . . . . . . . . . . . A. The Suzuki Reaction . . . . . . . . . . . . . . . B. The Negishi Reaction . . . . . . . . . . . . . . . C. The Stille Reaction . . . . . . . . . . . . . . . . D. The Sonogashira Reaction . . . . . . . . . . . . Other Palladium Catalysis in Ionic Liquids . . . . . A. Carbonylation of Aryl Halides . . . . . . . . . . B. Hydroarylation Reactions of Alkynes . . . . . . C. Alternating Copolymerization of Styrene and CO D. Biphasic Olefin Dimerization . . . . . . . . . . . E. Hydrogenation . . . . . . . . . . . . . . . . . . . F. Oxidation . . . . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . Abbreviations . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . .

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I INTRODUCTION Ionic liquids have become a focus of increasing interest over the last decade.1 Some of this interest is due to their possible use as ‘‘greener’’ alternatives to volatile organic solvents (see below). There is, however, also a great deal of fundamental interest in how the unusual solvent environment that they present might affect reactions conducted in them. Recently, there have been a number of excellent ionic liquid reviews concerning their chemical and physical properties,2 and applications in synthesis and catalysis.1,3,4 It is remarkable that in 1999 it was possible to 251 ADVANCES IN ORGANOMETALLIC CHEMISTRY VOLUME 51 ISSN 0065-3055/DOI 10.1016/S0065-3055(03)51006-1

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