Arylpalladium reagent

Arylation of olefins can also be achieved312 by treatment with an arylpalladium reagent that can be generated in situ by several313 methods (1) by treatment of an aryl bromide with a palladium-triarylphosphine complex (ArBr —> ArPdBr") 114 (2) by treatment of an aryl iodide315 with palladium acetate316 in the presence of a base such as tributylamine or... 

The arylation of olefins by the treatment with an arylpalladium reagent (known as the Heck reaction [71]), which can be generated in situ from palladium acetate and an aryl dihalide, in the presence of a base, has been applied to the synthesis of many PPVs, some of which are shown in Scheme 12 [72-74]. Ethylene is the most reactive olefin, but a variety of functional groups, attached to the double bond, such as CO2R, OR, and CN can be... 

The necessity of an activator reagent has been explicitly revealed using arylpalladium complexes containing silanyl residues, which are stable in the absence of activator, but immediately undergo transmetalation upon addition of an activator (Equation (16)) 273... 

The metal-bound carbon atom in organopalladium(II) complexes can formally react either as an electrophile or as a nucleophile. Treatment of arylpalladium(II) complexes with alkyl halides, for example, yields products of homo- or cross-coupling, possibly via intermediate formation of hexacoordinated Pd(IV) complexes [31,33] (Scheme8.1). Treatment of the same type of complex with alkyl Grignard reagents or other carbon nucleophiles, on the other hand, also yields the corresponding alkyl arenes via nucleophilic displacement of a ligand followed by reductive elimination (Scheme 8.1). 

A new preparative method for allylic indium(m) reagents via a reductive transmetallation of 7r-allylpalladium(n) or 7T-allylnickel(n) complexes with indium(i) salts is reported. This method enables the use of a wide variety of allylic compounds, such as allylic chlorides, acetates, and even allylic alcohols, in combination with Pd or Ni catalysts.43-50 7r-Allylpalladium(ii) resulting from the addition of arylpalladium(n) to allene is also transformed by metallic indium to the corresponding allylindium.51-54 Similarly, propargylindium(m) can be prepared from the corresponding propargyl alcohol derivatives.55-58... 

Oxidative biomimetic aryl coupling reactions of electron-rich (phenolic) aromatic hydrocarbons have occasionally been reported for selected examples see the reviews by Bringmann et al. [93 a] and the review on the ellagitannin chemistry by Quideau and Feldman [93b]. Oxidative homocoupling has also been achieved with palladium(II) acetate via the 5-arylpalladium complexes [78 d], but stoichiometric amounts of the palladium reagents are often required and acetylation can occur as a side reaction [93a]. 

Aromatic compounds can react with Pd(II) species, typically Pd(OAc)2, via cleavage of their C-H bonds to give arylpalladium(II) species (Scheme 1, mechanism D). Therefore, the arylation of alkenes can be performed directly using arenes and aromatic heterocycles [10, 11]. In this arylation, halogenation of arenes can be omitted, but an oxidizing reagent for the reoxidation of Pd(0) to Pd(II) should be added to make the reaction catalytic. 

D.ii.c. Termination by Boranes (Heck-Suzuki Cascade). Similarly, boranates and boronates are suitable reagents for the transfer of aryl or alkenyl groups to rr-alkyl-, o--alkenyl-, and o--arylpalladium complexes and hence are ideal for termination of cascade reactions. Tetraphenylboranate is the reagent of choice for the phenylation of organopaUadium intermediates (Scheme 28). ... 

In this novel domino sequence, norbornene (or norbomadiene) acts as a promoter as well as a reaction partner. It enters and exits the catalytic cycle and is eventually incorporated in the product, and therefore the reaction requires an excess of this reagent. The standard Pd-catalyzed/norbomene-mediated ortho alkylation of the aryl iodide with the alkyne would form the arylpalladium species 146 (Scheme 3.36). Intramolecular carbopalladation onto the tethered alkyne unit gives vinylpalladiuml47. Intermolecularcarbopalladationwitha moleculeofnorbornene... 

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