Negishi reaction, transition metal

Negishi previously reported that a wide variety of Lewis-acidic compounds catalyzed hydrozirconation of alkenes such as 1-decene 108 with /-BuZrCp2Cl.126 It was found that the reaction of 1-decene with 1.1 molar equiv. of TIB A, in the presence of 2-5 mol% of chlorine-containing late transition metals, led to the formation of 1-iododecane 110 after treatment of the product with iodine (Table 9). 

Transition Metal Catalysis in tonic Liquids 241 5.2.4.4 Heck, Suzuki, Stille, and Negishi coupling reactions... 

The insight that zinc ester enolates can be prepared prior to the addition of the electrophile has largely expanded the scope of the Reformatsky reaction.1-3 Substrates such as azomethines that quaternize in the presence of a-halo-esters do react without incident under these two-step conditions.23 The same holds true for acyl halides which readily decompose on exposure to zinc dust, but react properly with preformed zinc ester enolates in the presence of catalytic amounts of Pd(0) complexes.24 Alkylations of Reformatsky reagents are usually difficult to achieve and proceed only with the most reactive agents such as methyl iodide or benzyl halides.25 However, zinc ester enolates can be cross-coupled with aryl- and alkenyl halides or -triflates, respectively, in the presence of transition metal catalysts in a Negishi-type reaction.26 Table 14.2 compiles a few selected examples of Reformatsky reactions with electrophiles other than aldehydes or ketones.27... 

Chapter 5 includes complete coverage of the transition metals-mediated carbon-carbon bond forming reactions. Pd-, Ni-, Cr-, Zr- and Cu-catalyzed reactions such as Heck, Negishi, Sonogashira, Suzuki, Hiyama, Stille, Kumada reactions are covered in adequate details including the applications of these reactions in organic synthesis. 

Consequently, to narrow the definition a bit further, we will adhere to Negishi s suggestion and define cross-coupling reactions as those that follow some variation of the mechanism depicted in Scheme 1 (where Mt is a transition metal, L is an ancillary hgand see Ancillary Ligand), and n is the oxidation state of the reduced metal in the catalytic cycle). This mechanism is supported by stoichiometric studies on isolated metal complexes (mostly where Mt = Pd, n = 0, L = triphenylphosphine) thought to be the intermediates in this cycle. 

Negishi, E., King, A. O., Okukado, N. Selective carbon-carbon bond formation via transition metal catalysis. 3. A highly selective synthesis of unsymmetrical biaryls and diarylmethanes by the nickel- or palladium-catalyzed reaction of aryl- and benzylzinc derivatives with aryl halides. J. Org. Chem. 1977,42, 1821-1823. 

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