Biaryl arenediazonium salt

Palladium catalysts have been found which are effective in the Suzuki coupling reaction of arylboronic acids with aryl chlorides carrying electron-withdrawing groups.73 Biaryls may also be synthesized by cross-coupling of arylboronic acids with arenediazonium salts.74,75 There has been a report of the polymer-bound palladium-catalysed Suzuki coupling of aryl triflates with organoboron compounds.76 Arylbor-onates may themselves be synthesized by the palladium-catalysed reactions of... 

Gomberg-Bachmann biphenyl synthesis. Reaction of stable arenediazonium tet-rafluoroborates or hexafluorophosphates in an aromatic solvent with potassium acetate (2 equiv.) and a phase-transfer catalyst results in biar Is in high yield. Crown ethers, Aliquat 336, and tetrabutylammonium hydrogen sulfate arc all effective catalysts. The reaction is useful for synthesis of unsymmetrical biaryls. The ortho-isomer predominates in reactions with a monosubstituted benzene. The most selective method is to couple a substituted arenediazonium salt with a symmetrical arene. 

The first example of an intramolecular homolytic aromatic substitution was published by Pschorr more than a century ago [34], Biaryls were prepared by intramolecular homolytic substitution of arenes by aryl radicals which were generated by treatment of arenediazonium salts with copper(I) ions (Pschorr reaction). Later it has been shown that similar reactions can be conducted under basic conditions or by photochemical or thermal decomposition of the diazonium salts [35]. Electrochemical reduction [36], titanium (III) ions [37], Fe(II)-salts [38], tetrathiafulvalene... 

Other variations of the biaryl synthesis involve KiArBF ] and diaryliodonium salts or arenediazonium salts. ... 

The chemistry of pyridylphosphines has been reviewed. Further studies have appeared of the reactions of phosphines bearing 2-pyridyl or 2-benzothiazolyl substituents with butyl-lithium, which result in the formation of biaryl coupling products via an initial nucleophilic attack at phosphorus. A study of the de-diazoniation of arenediazonium salts using triphenylphosphine (and trialkylphosphites) indicates that the reactions proceed via a radical-chain mechanism, initiated by single electron transfer from the phosphine to the diazonium salt, to give... 

Arenediazonium salts ArN2Bp4 are an excellent substrate available from aromatic amines for carrying out oxidative addition under mild conditions. The desired cross-coupling with aryl(trifluoro)borates (ArBp3)K is achieved at room temperature with 5 mol% of Pd(OAc)2 or with the paradacycle shown in Eq. 26 (Eq. 46). Biaryl coupling of arene... 

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