Carbon-Carbon Cross-Coupling Reactions
Chemical processes have played a vital role in the evolution of human civilization. Catalysts have been known for centuries even before mankind understood the chemical processes. From the fermentation of wine to vinegar, conversion of starch to sugar, to
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Carbon-Carbon Cross-Coupling Reactions
9.1 Introduction Chemical processes have played a vital role in the evolution of human civilization. Catalysts have been known for centuries even before mankind understood the chemical processes. From the fermentation of wine to vinegar, conversion of starch to sugar, to the initial industrial application of catalysts to produce sulphuric acid, catalytic industry has revolutionized our world. They are used in numerous processes including petrochemical industry for polymerization, oxidation, hydrogenation; production of fertilizers, catalytic convertors in cars, green chemistry; also, production of drugs in pharmaceutical industry. In this chapter, we will try to describe the later application that is revolutionizing the health care industry. Ongoing demand for new drugs and the need to produce drugs at cheaper prices have stimulated tremendous efforts to develop novel catalysts in pharmaceutical industry [1]. The diverse materials employed as catalysts include metal oxide, metal complexes, organic and inorganic polymers, as well as biocatalysts and photocatalysts. An important class of reactions are the transition-metal catalyzed crosscoupling reactions that have wide-ranging applications such as in producing active pharmaceutical ingredients (API) [2]. As an example, Singulair is an important drug used for allergies and asthma and is marketed by Merck. Its active ingredient montelukast sodium requires a Heck reaction using aryl-halide catalyzed by a Pd catalyst [3–5]. In fact, Pd-catalyzed cross-coupling reactions account for almost 40% of cross-coupling reactions involving C–C bond formation in chemistry and pharmaceutical industry [6–49]. It is interesting to point out that nickel was used in cross-coupling reactions in early 1900’s whereas the use of Pd started in 1950’s. One of the objectives of this chapter is to highlight how recent efforts have led to novel Pd catalysts used for production of pharmaceuticals and what kind of attempts have been conducted to replace palladium by cheaper metals. Fundamental information on the mechanisms underlying metal cluster catalysis is critical to these developments.
© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2020 Z. Luo and S. N. Khanna, Metal Clusters and Their Reactivity, https://doi.org/10.1007/978-981-15-9704-6_9
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9 Carbon-Carbon Cross-Coupling Reactions
9.2 Cross-Coupling Reactions by Metal Catalysts Transition metal catalysts have long been used in organic and organometallic industry. Their use for coupling reaction can be traced back to the late 19th century [50]. One of the early reactions was Ullmann reaction that converts aryl halides to biphenyl species via copper catalysis [51–53]. While early work used copper catalysts, a copper/palladium catalyst was introduced to the coupling reaction by Heck in 1968 [54]. During the 70s’ and 80s’, several Pd catalyzed cross-coupling processes had been discovered and a summary of the reactions is given
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