Selective cleavages of carbon-carbon bonds catalyzed by transition-metal complexes have been shown to be increasingly versatile tools for organic synthesis allowing for complementary synthetic strategies Numerous examples of transition-metal catalyzed C-C bond activations of three- and four-membered ring systems have been reported These strained rings have been shown to engage in a variety of new ring-opening rearrangements and cycloaddition reactions leading to valuable structures Besides strain-driven transformations, other facilitating strategies to enforce the C-C bond activation of unstrained molecules have been developed as well While the variety of different transformations is less abundant, they concentrate on chelation-assisted reactions using appropriate permanent or transient directing groups In particular, the cleavage and subsequent functionalization of the C-CN bonds and decarbonylation processes operating by an excision of carbon monoxide from ketone derivatives have witnessed a large progress

Catalytic C-C Bond Activations via Oxidative Addition to Transition Metals.

It has been established that dihalodiphosphinenickel(II) complexes exhibit extremely high catalytic activity for selective cross-coupling of Grignard reagents with aryl and alkenyl halides. This catalytic reaction can be employed in synthetic practice for reasons of simple procedures, mild reaction conditions, high yields and high purity of the coupling products, and the wide applicability to reactions involving primary and secondary alkyl (regardless of the presence or absence of β-hydrogen (s)), aryl, and alkenyl Grignard reagents and nonfused, fused, and substituted aromatic halides and haloolefins. Limitations lie in sluggish reactions between alkyl Grignard reagents and dihaloethylenes. The most effective catalysts are [Ni{(C6H5)2P(CH2)3P(C6H5)2}Cl2] for alkyl and simple aryl Grignard reagents, [Ni{(CH3)2P(CH2)2P(CH3)2}Cl2] for alkenyl and allylic Grignard reagents and [Ni{P(C6H5)3}2-Cl2] for sterically hindered aryl Grignard reagents and halides. Great stabilizing effects of phosphine ligands on the...

Nickel-phosphine complex-catalyzed Grignard coupling. I. Cross-coupling of alkyl, aryl, and alkenyl Grignard reagents with aryl and alkenyl halides: General scope and limitations.

Phosphonium cation-based ionic liquids (ILs) are a readily available family of ILs that in some applications offer superior properties as compared to nitrogen cation-based ILs. Applications recently investigated include their use as extraction solvents, chemical synthesis solvents, electrolytes in batteries and super-capacitors, and in corrosion protection. At the same time the range of cation–anion combinations available commercially has also been increasing in recent years. Here, we provide an overview of the properties of these interesting materials and the applications in which they are appearing.

Phosphonium-Based Ionic Liquids: An Overview

Publisher Summary The liquid phase oxidation of hydrocarbons by molecular oxygen forms the basis for a wide variety of petrochemical processes including the manufacture of phenol and acetone from cumene, adipic acid from cyclohexane, terephthalic acid from p -xylene, acetaldehyde and vinyl acetate from ethylene, and propylene oxide from propylene. The majority of these processes employ catalysis by transition metal complexes to attain maximum selectivity and efficiency. This chapter describes the subject of metal-catalyzed oxidations of organic compounds in the liquid phase, largely within a mechanistic framework. A better understanding of the catalytic action of metal complexes is essential from the point of view of increasing selectivity and efficiency. Metal-catalyzed oxidations may be conveniently divided into two types—homolytic and heterolytic. The homolytic catalysis involves soluble transition metal salts (homogeneous), such as the acetates or naphthenates of Co, Mn, and Cu, or the metal oxides (heterogeneous). Heterolytic catalysis involves reactions of organic substrates coordinated to transition metals.

Metal-Catalyzed Oxidations of Organic Compounds in the Liquid Phase: A Mechanistic Approach

Conventional organic synthesis has been mainly based upon the reactivities of π-bonds and polar σ-bonds. Carbon–carbon single bonds are nonpolar and generally far less reactive. Although they remain intact under most reaction conditions, it is possible to activate and cleave them if suitable organometallic compounds or metal catalysts are applied. Such C–C single bond cleavage reactions are attracting increasing attention in the context of synthetic chemistry because they provide a unique and more straightforward route from readily available substances to targets, while requiring significantly fewer steps. The present Perspective aims to exemplify the potential of metal-catalyzed C–C single bond cleavage for organic synthesis.

A. R. Kane

Papers

Reactivity of trialkylphosphine complexes of platinum(O)

Reaktivitaet von trialkylphosphinplatin(0)-komplexen