Kumada coupling

In organic chemistry, the Kumada coupling is a type of cross coupling reaction, useful for generating carbon–carbon bonds by the reaction of a Grignard reagent and an organic halide. The procedure uses transition metal catalysts, typically nickel or palladium, to couple a combination of two alkyl, aryl or vinyl groups. The groups of Robert Corriu and Makoto Kumada reported the reaction independently in 1972. The reaction is notable for being among the first reported catalytic cross-coupling methods. Despite the subsequent development of alternative reactions (Suzuki, Sonogashira, Stille, Hiyama, Negishi), the Kumada coupling continues to be employed in many synthetic applications, including the industrial-scale production of aliskiren, a hypertension medication, and polythiophenes, useful in organic electronic devices. The first investigations into the catalytic coupling of Grignard reagents with organic halides date back to the 1941 study of cobalt catalysts by Morris S. Kharasch and E. K. Fields. In 1971, Tamura and Kochi elaborated on this work in a series of publications demonstrating the viability of catalysts based on silver, copper and iron. However, these early approaches produced poor yields due to substantial formation of homocoupling products, where two identical species are coupled. These efforts culminated in 1972, when the Corriu and Kumada groups concurrently reported the use of nickel-containing catalysts. With the introduction of palladium catalysts in 1975 by the Murahashi group, the scope of the reaction was further broadened. Subsequently, many additional coupling techniques have been developed, culminating in the 2010 Nobel Prize in Chemistry recognized Ei-ichi Negishi, Akira Suzuki and Richard F. Heck for their contributions to the field. According to the widely accepted mechanism, the palladium-catalyzed Kumada coupling is understood to be analogous to palladium's role in other cross coupling reactions. The proposed catalytic cycle involves both palladium(0) and palladium(II) oxidation states.