Polyhalides synthesis

The synthesis of polyhalide salts, R4NX , used in electrophilic substitution reactions, are described in Chapter 2 and H-bonded complexed salts with the free acid, R4NHX2, which are used for example in acid-catalysed cleavage reactions and in electrophilic addition reactions with alkenes, are often produced in situ [33], although the fluorides are obtained by modification of method I.I.I.B. [19, 34], The in situ formation of such salts can inhibit normal nucleophilic reactions [35, 36]. Quaternary ammonium chlorometallates have been synthesized from quaternary ammonium chlorides and transition metal chlorides, such as IrClj and PtCl4, and are highly efficient catalysts for phase-transfer reactions and for metal complex promoted reactions [37]. 

In 1967, an original synthesis of 1,4-dilithio-1,4 diphenyl-1,3-butadiene (DDB) from 1,1-dimethyl-2,5-diphenylsilole (see equation 17 below) was proposed by Gilman and coworkers34. This dilithium reagent reacts with polyhalides R EX4 to yield 2,5-diphenylmetalloles (26, E = Si34,35, Ge36, Sn34) (Scheme 6). 

Reactions. - The reactions of diorganoiodophosphines with varying quantities of iodine have been studied by NMR techniques, which indicate the formation of a dialkyldi-iodophosphonium iodide as the initial product, followed by polyhalide anion formation in the presence of excess iodine. A modified McCormack synthesis of 3-silylated phosphol-3-enes (168) from phenyl-dichlorophosphine and 2-silylated 1,3-butadienes has been described. The reaction is carried out in the presence of a small amount of copper stearate in acetic anhydride at 50 °C, these conditions preventing the complete desilylation observed under standard conditions. The consecutive reaction of lithium phenylacetylide with triphenylborane and diphenylchlorophosphine results in the formation of the intramolecularly coordinated phosphino-borane (169). Treatment of the alkoxyvinyldichlorophosphines (170) with Grignard reagents... 

An improved electrochemical procedure for the synthesis of alkoxyphos-phonium salts has been reported. Salts bearing a wide range of unusual counterions have been prepared, including phenoxide, polyhalide, halogeno-metallate, di-O-alkyl dithiophosphate, herbicidal phosphonate, and ylide-anions. ... 

A combination of selective and stepwise cross-couphngs of polyhalides with protected acetylenes and deproteclions under various conditions leads to the synthesis of unsym-metrically substituted polyelhynylated arenes or olefins as shown in Schemes 37, ... 

Ruthenium triphenylphosphine complex Synthesis of polyhalides from ethylene derivs. 

Ruthenium triphenylphosphine complex Synthesis of polyhalides from ethylene derivs. s. 19, 116 suppl. 29... 

A soln. of tetrabromoethylene in tetrahydrofuran allowed to react with a suspension of Mg in trimethylchlorosilane and tetrahydrofuran, more trimethyl-chlorosilane added, and refluxed 2 hrs. bis(trimethylsilyl) acetylene. Y 60.2%. —Polyhalides considered inert or unsuitable to Grignard synthesis react satisfactorily by the above in situ procedure. F. e. s. R. L. Merker and M. J. Scott, Am. Soc. 85, 2243 (1963). 

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