Perfluoroaryl derivs

Perfluoropropynyl [15, 26, 27] and perfluorovinyl [16, 28-30]-lithium and -magnesium are considerably more stable than perfluoroalkyl derivatives, whilst the corresponding perfluoroaryl derivatives may be used as effectively as in the hydrocarbon series, and direct syntheses involving iodo compounds are also possible (Figure 10.3). 

Scheme S. Addition-elimioation mechanism of fonnation of perfluoroaryl derivatives.

Scheme 5. Addition-elimination mechanism of formation of perfluoroaryl derivatives.

Base-free complexes of Ni of composition NiR2 or Ni(R)X, where R is a n-bound organic fragment and X is a simple anion (halide, pseudohalide, hydroxide) are in general very unstable species, and their isolation remains very rare. However, the chemistry of anionic ate complexes [NiR2+ ] and [NiR2(/r-X)]2 is growing steadily, especially in the case of the perfluoroaryl derivatives (Table 1). This section will cover all these compounds as well as their adducts... 

In polyfluorobenzenes having other substituents in addition to fluorine, including per-fluoroalkyl or perfluoroaryl groups, the elimination of only one fluorine atom proceeds more readily, with the para position in pentafluorobenzene derivatives being replaced first. The reaction conditions used for monosubstitution of fluorine depend markedly on the substrate and on the nucleophilic agent chosen. In most cases the reaction can be carried out in ethylene glycol/pyridine using sodium hydroxide as base (Table 3). 

TRIS-PERFLUOROARYL BORANE DERIVATIVES B(C6F5)3 AND RELATED COMPOUNDS... 

Phenolic substrates are not readily reduced to benzene derivatives, and this fact can be used to effect the transformation of methyl or benzyl ethers of phenols to their silyl ethers with elimination of CH4 or toluene as the only by-products. These studies include detailed mechanistic studies that support and corroborate our experiments and support the silane activation mechanism. The reaction is clean and high yielding enough to be applied towards the functionalization of the periphery of carbosilane dendrimers with perfluoroaryl borane moieties (Scheme 25).196... 

V. Tris-perfluoroaryl Borane Derivatives B(C F5)3 and Related Compounds. 19... 

Perfluoroaryl thiophene derivatives 195-197 were obtained by nucleophilic aromatic substitution via Ihienyllithium intermediates 194. The reaction is quite simple and is widely used for the preparation of various fluoroaromatics [59]. 

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