Nickel Grignard cross-coupling

Figure 3.49. Chiral ligands that exhibit high enantioselectivity in the nickel-catalyzed Grignard cross-coupling reaction of vinyl bromide (or chloride) with 1-phenylethylmagne-sium chloride.

Asymmetric Grignard Cross-Coupling Catalyzed by Chiral Phosphine-Nickel Complexes 73)... 

More recent review Hayashi, T. Asymmetric Grignard Cross-Coupling Catalyzed by Chiral Phosphine-Nickel and Phosphine-Palladium Complexes, in Asymmetric Reactions and Processes in Chemistry (Eliel, E. L., Otsuka, S. ed.), American Chemical Soc. Symp. Series Vol. 185, p. 177 (1982)... 

The effect of the ligand on the stereochemical course of a reaction catalyzed by a transition metal compound can be significant. For example, in the nickel-catalyzed cross-coupling reactions of alkyl Grignard reagents and aryl halides, the effect of changing the ligands on the metal is summarized in Fig. 13 (66, 67). 

In 1971, a year before the groups of Corriu and Kumada [5] independently reported the groundbreaking work on the topic of nickel-catalyzed cross-coupling reactions of aryl and vinyl halides with Grignard reagents, Tamura and Kochi described an iron-catalyzed vinylation reaction of Grignard reagents with vinyl halides (Scheme 5.1) [6]. 

Scheme 30. Nickel-catalyzed cross-coupling of O-aryl carbamates and triflates with Grignards electronic and steric effects.

A further advantage is the possible in situ generation of catalysts from simple metal salts or complexes (e. g., Ni(OR)2, PdCU) and azolium salts. The nickel-catalyzed Grignard cross-coupling of aryl chlorides at room temperature [123] and the activation of aryl fluorides [136] are convincing examples. 

The first substituted PTV derivatives poly(3-methoxy-2,5-thienylene vinylene) and poly(3-ethoxy-2,5-thienylene vinylene) 84 were synthesized by Elsenbaumer in the late 1980s [125], The method employed was a step-growth condensation using a nickel-mediated cross-coupling reaction between a Grignard reagent and a dichloroethene (Scheme 1-27). The materials obtained were deep blue solids, but the majority of the sample was insoluble in common organic solvents. End-... 

In the first reported examples of the asymmetric Grignard cross-coupling, a nickel complex coordinated with (-)-DIOP (1) was used as catalyst [6,7]. Reaction of 1-phenylethyl (2) and 2-butyl (3) Grignard reagents with vinyl chlo-... 

The compound 12 is an extremely useful ligand for nickel-catalyzed Grignard cross-coupling reactions and allows the enantioselective synthesis of biaryls in over 90%ee36,37 (Sections D. 1.1.3. and B.2.). 

Dithioacetals are also considered as dication syntons. For example, bisdithioac-etals are employed for the nickel catalyzed cross coupling reaction with Grignard reagents to give homoallylic dithioacetals (Scheme 3.80) [153], In this reaction, only one of the dithioacetal moieties is the reactive site and a chelate intermediate is proposed. 

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