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Advances in transition metal (Pd, Ni, Fe)-catalyzed cross-coupling reactions using alkyl-organometallics as reaction partners.

Palladium-catalyzed C-C and C-N bond-forming reactions are among the most versatile and powerful synthetic methods. For the last 15 years, N-heterocyclic carbenes (NHCs) have enjoyed increasing popularity as ligands in Pd-mediated cross-coupling and related transformations because of their superior performance compared to the more traditional tertiary phosphanes. The strong sigma-electron-donating ability of NHCs renders oxidative insertion even in challenging substrates facile, while their steric bulk and particular topology is responsible for fast reductive elimination. The strong Pd-NHC bonds contribute to the high stability of the active species, even at low ligand/Pd ratios and high temperatures. With a number of commercially available, stable, user-friendly, and powerful NHC-Pd precatalysts, the goal of a universal cross-coupling catalyst is within reach. This Review discusses the basics of Pd-NHC chemistry to understand the peculiarities of these catalysts and then gives a critical discussion on their application in C-C and C-N cross-coupling as well as carbopalladation reactions.

Palladium Complexes of N-Heterocyclic Carbenes as Catalysts for Cross-Coupling Reactions—A Synthetic Chemist's Perspective

Nickel-Catalyzed Cross-Couplings Involving Carbon-Oxygen Bonds Brad M. Rosen, Kyle W. Quasdorf, Daniella A. Wilson, Na Zhang, Ana-Maria Resmerita, Neil K. Garg,* and Virgil Percec* Roy & Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, United States Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States

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Nickel-Catalyzed Cross-Couplings Involving Carbon-Oxygen Bonds

Despite the problems inherent to metal-catalyzed cross-coupling reactions with alkyl halides, these reactions have become increasingly important during the last few years. Detailed mechanistic investigations have led to a variety of novel procedures for the selective cross-coupling of non-activated alkyl halides bearing β hydrogen atoms with a variety of organometallic nucleophiles under mild reaction conditions. This Minireview highlights selected examples of metal-catalyzed coupling methods and is intended to encourage chemists to exploit the potential of these approaches in organic synthesis.

Catalysts for Cross‐Coupling Reactions with Non‐activated Alkyl Halides

Organomagnesium reagents occupy a central position in synthetic organic and organometallic chemistry. Recently, the halogen-magnesium exchange has considerably extended the range of functionalized Grignard reagents available for synthetic purposes. Functional groups such as esters, nitriles, iodides, imines, or even nitro groups can be present in a wide range of aromatic and heterocyclic organomagnesium reagents. Also various highly functionalized alkenyl magnesium species can be prepared. These recent developments as well as new applications of organomagnesium reagents in cross-coupling reactions and amination reactions will be covered in this Review.

Highly functionalized organomagnesium reagents prepared through halogen-metal exchange.

In the presence of Bu4NI (3 equiv) and 4-fluorostyrene (20 mol %), unreactive primary and secondary alkylzinc iodides undergo nickel-catalyzed cross-couplings with various primary alkyl iodides or bromides. More reactive secondary dialkylzincs and the mixed zinc organometallics RZnTMSM undergo the cross-coupling reaction in the absence of Bu4NI. The bicyclic secondary diorganozinc 6 prepared via boron−zinc exchange reacts with high retention of configuration. Free NH-groups are tolerated in the cross-coupling allowing the synthesis of aminated products.

Nickel-catalyzed cross-coupling between functionalized primary or secondary alkylzinc halides and primary alkyl halides

New Efficient Nickel- and Palladium-Catalyzed Cross-Coupling Reactions Mediated by Tetrabutylammonium Iodide

Functionalized magnesium reagents have been prepared via an iodine-magnesium exchange. These reagents can be either trapped directly with aldehydes or transmetallated to copper or zinc to participate in cross-coupling reactions. The iodine-magnesium exchange, represent a unique method for the preparation of aryl and heteroaryl magnesium reagents.

Preparation and Reactions of Functionalized Arylmagnesium Reagents

Preparation of polyfunctional heterocycles using highly functionalized aminated arylmagnesium reagents as versatile scaffolds.

Improved nickel-catalyzed cross-coupling reaction conditions between ortho-substituted aryl iodides/nonaflates and alkylzinc iodides in solution and in the solid-phase

Anne Eeg Jensen

Papers

Nickel-catalyzed cross-coupling between functionalized primary or secondary alkylzinc halides and primary alkyl halides

New Efficient Nickel- and Palladium-Catalyzed Cross-Coupling Reactions Mediated by Tetrabutylammonium Iodide

Preparation and Reactions of Functionalized Arylmagnesium Reagents

Preparation of polyfunctional heterocycles using highly functionalized aminated arylmagnesium reagents as versatile scaffolds.

Improved nickel-catalyzed cross-coupling reaction conditions between ortho-substituted aryl iodides/nonaflates and alkylzinc iodides in solution and in the solid-phase