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Do you know? How to use nickel catalyst to create a leapfrog revolution in chemistry in 1972!
In organic chemistry, the Kumada coupling reaction is an important cross-coupling reaction that can effectively generate carbon-carbon bonds. This reaction proceeds through the reaction of a Grignard reagent with an organic halogen, and transformation metal catalysts, especially nickel or palladium, are widely used to couple two alkyl, aryl or vinyl groups. In 1972, two scientists, Robert Corriu and Makoto Kumada, independently reported this reaction, which made Kumada coupling an important tool to promote the synthesis of carbon-carbon bonds and continues to play an important role in synthetic applications. Roles such as the synthesis of aliskiren, a drug that lowers hypertension, and polythiophenes in organic electronic devices.
"Kumada coupling is of great significance in the field of chemical synthesis because it provides a universal route for the efficient synthesis of carbon-carbon bonds."
History
The history of Kumada coupling can be traced back to 1941, when Morris S. Kharasch and E. K. Fields conducted research on cobalt catalysts. However, in 1971, further studies of this work by Tamura and Kochi showed the feasibility of silver, copper, and iron catalysts. Nonetheless, these early methods resulted in low yields due to the tedious generation of co-coupled products. In 1972, two groups of researchers, Corriu and Kumada, simultaneously published research on the use of nickel catalysts. These results quickly advanced the application potential of this reaction. By 1975, Murahashi and others introduced a palladium catalyst, further expanding the scope of the reaction.
Reaction mechanism
Palladium catalysis
Based on current understanding, the palladium-catalyzed Kumada coupling reaction is believed to be similar to other cross-coupling mechanisms. Its catalytic cycle involves the oxidation states of palladium, including palladium (0) and palladium (II). Initially, the electron-rich Pd(0) catalyst inserts into the R–X bond of the organohalogen and undergoes oxidative addition to form the organo-Pd(II)-complex. Subsequently, transmetallation with Grignard reagents forms heterogeneous organometallic complexes. Before proceeding to the next step, isomerization is required to convert the organic ligands into positions adjacent to each other. Ultimately, a reductive elimination reaction that forms carbon–carbon bonds and releases cross-coupling products regenerates the Pd(0) catalyst.
Nickel Catalysis
The current understanding of the mechanism of nickel-catalyzed Kumada coupling reactions is still limited, as this reaction may exhibit different mechanisms depending on different reaction conditions and nickel ligands. In general, nickel-catalyzed Kumada coupling can also be analogized to the reaction mechanism of palladium, but sometimes the same explanation cannot be used to explain all observed phenomena. Some studies have shown that nickel may form a Ni(II)-Ni(I)-Ni(III) catalytic cycle.
Application
Synthesis of Aliskiren
Kumada coupling reactions have broad application potential in large-scale industrial processes, such as drug synthesis. It was used to build the carbon skeleton of aliskiren, a drug used to treat high blood pressure.
Synthesis of polythiophene
In addition, Kumada coupling has shown potential in the synthesis of conjugated polymers, such as polyalkylthiophenes (PAT), which have diverse applications in organic solar cells and light-emitting diodes (LEDs). In 1992, McCollough and Lowe developed the first synthesis of reformed polyalkylthiophenes using the Kumada coupling scheme, and since then the yields and conditions of this synthesis have been improved.
The emergence of Kumada coupling reaction has changed the pattern of organic synthesis and promoted research and application in the chemical community. Will more and more innovative reaction methods be developed in the future to continue to promote the progress and development of chemistry?
