Transition metal oxidative cross-coupling reactions

Much work has been directed towards the synthesis of thiophene oligomers and polymers. This is due to the current interest in research on conducting polymers and molecular electronics (92CRV711). Two main approaches have been used for making such polymers (i) chemical (e.g. FeCl3) or electrochemical oxidation of monomeric thiophenes and (ii) transition metal-catalyzed cross-coupling reactions. 

GY Li. The First Phosphine Oxide Ligand Precursors for Transition Metal Catalyzed Cross-Coupling Reactions C-C, C-N, and C-S Bond Formation on Unactivated Aryl Chlorides. Angew Chem 113 1561-1564, 2001 Angew Chem Int Ed 40 1513-1516, 2001. 

Phosphine oxides have been extensively employed as ligands in transition-metal catalyzed cross-coupling reactions. However, their property to act as a structural mimic of carboxylate ions make them important preligands in C-H bond activation. Ackermann and co-workers have... 

The scope of transition metal-catalysed cross-coupling reactions involving N-tosylhydrazones has been broadened. While IV-tosylhydrazones cross-couple with trialkylsilylethynes to form C -C s bonds under Cu(I) catalysis,i° Pd(0) catalysis has been used to induce (i) their oxidative cross-coupling reactions with allylic alcoholsi and (ii) their cross-coupling with cyclopropyl halides, giving rise to... 

Preparations of all these organic materials involve the constmction of new carbon-carbon bonds and have prompted the development of many catalytic cross-coupling reactions. One of the most reliable synthetic methods to form carbon-carbon bonds is transition metal-catalyzed cross-coupling between organo-metallic nucleophiles and electrophilic organic halides or pseudohalides, respectively (Scheme 2a). The mechanisms of common cross-coupling reactions such as the Suzuki, Negishi, or Stille catalysis can be described by a catalytic cycle, differ in detail, but all include three main steps in the order oxidative addition, transmetallation, and reductive elimination (Scheme 1). 

Liu C, Zhang H, Shi W, Lei A (2011) Bond formations between two nucleophiles transition metal catalyzed oxidative cross-coupling reactions. Chem Rev 111 1780-1824... 

The elimination of a hydrogen atom positioned on a carbon to the central metal constimtes an important reaction in transition metal catalysis. In the classical example, an alkylmetal intermediate is reversibly converted to an alkene and a metaUiydride (scheme 1.12). Despite the fact, that the resulting hydridometal complex can be exploited in various catalytic processes including polymerization reactions, [57] cycloisomerizations, [58] annulations, [59] etc., the ]S-hydride elimination is often considered undesired in transition metal catalyzed cross couplings. Thus, efforts have often been concentrated towards the prohibition of this fundamental reaction [60]. Nevertheless, the ]S-hydride elimination is a vital transformation in a number of catalytic processes including the ene-yne coupling reported by Trost [61] and Skrydstrup, [62] oxidation of alcohols, [63] the Heck reaction etc [64]. 

In contrast to the transition metals, where there is often a change in oxidation level at the metal during the reaction, there is usually no change in oxidation level for boron, silicon, and tin compounds. The synthetically important reactions of these three groups of compounds involve transfer of a carbon substituent with one (radical equivalent) or two (carbanion equivalent) electrons to a reactive carbon center. Here we focus on the nonradical reactions and deal with radical reactions in Chapter 10. We have already introduced one important aspect of boron and tin chemistry in the transmetallation reactions involved in Pd-catalyzed cross-coupling reactions, discussed... 

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