Palladium-Catalyzed Cross-Coupling with Grignard Reagents

2 Palladium-Catalyzed Cross-Coupling with Grignard Reagents 

SCHEME 19.18 Palladium-catalyzed cross-coupling of Grignard reagents (1976). 

---

The metal-catalyzed cross-coupling of Grignard reagents with organylhalides is mostly referred as "Kumada reaction". In most cases. Nickel catalysts have been employed, but they are not subject of this chapter. However, there are many cases based on the pioneering works of Sekiya and Ishikawa, Kumada and Hayashi, where palladium complexes are used with success " (Scheme 5-102, Scheme 5-103, Experimental Procedure below ). The POPd2 system (see also Figure 5-12) delivers... 

In the early 1980s, one of the first preparations of substituted allenes was reported, which employed a palladium-catalyzed cross-coupling reaction of allenyl halides [9]. In this study, allenyl bromides 13 and various Grignard reagents 14 were coupled in the presence of catalytic amounts of a Pd(0) species, generated in situ by reduction of a Pd(II) salt. Trisubstituted allenes 15 were obtained with high regioselectivity (allene 15 alkyne 16 = 90 10 to 99 1) (Scheme 14.5). 

The Kumada cross-coupling reaction (also occasionally known as the Kharasch cross-coupling reaction) is a nickel- or palladium-catalyzed cross-coupling reaction of a Grignard reagent with an organic halide, triflate, etc. 

The enantioselective desymmetrization strategy can also be used for the palladium-catalyzed cross-coupling reactions with Grignard reagents. Thus, in the... 

Murahashi, S.-l. Palladium-catalyzed cross-coupling reaction of organic halides with Grignard reagents, organolithium compounds and heteroatom nucleophiles. J. Organomet. Chem. 2002, 653, 27-33. 

Selective cross-coupling reactions between C(sp ) and C(5p ) centers had been one of the most difficult tasks in carbon-carbon bond synthesis until the early 1970s, when it was first reported that iron, nickel, palladium and copper - catalysts are extremely effective for cross-coupling of Grignard reagents with organic halides. Now, nearly 20 years later, transition metal catalyz cross-coupling has become the reaction of first choice for this purpose. 

---