Benzyl phosphonium ions

Benzyl phosphonium ions, polymer-bound, alkenes prepared, l65t Benzyne... 

The selective and facile cleavage of the benzylic ether linkages of 1,2,3 or 4 is accomplished by treatment with iodotrimethylsilane to form the corresponding benzylic iodide. Further addition to these iodide derivatives of 1 affords dendrimers of generation 1 with phosphonium ion sites at the periphery. Such a strategy is conducted up to generation 3 with a phosphine or a phosphonium core (Scheme 3). 

The results of the pulse radiolysis in aqueous solution of substituted phosphonium ions have been investigated38 in addition to those of the electrode reduction of benzyl triphenyl-phosphonium ion39 and quaternary phosphonium salts with hydrated electrons40-42. The radiolysis of methyltriphenylphosphonium, dimethyldiphosphonium and trimethyl-phenylphosphonium ions in neutral aqueous solutions leads to phosphoranyl radicals... 

Reactions of benzylic phosphonium salts were carried out at 20 °C using 10 mL of methylene chloride, 1.5 mmol of the polymeric phosphonium salt, and 3 mL of 50% NaOH (aq). The linear polystyrene had a MW of 150,000 with 2.7 mmol of -PPh2/g of polymer. The cross-linked polystyrene contained 3.0-3.5 mmol of -PPh2/g of polymer. The halogenated phosphonium ion was prepared from phos-phinated polystyrene having 0.4 mequiv of -PPh2/g of polymer and was allowed to react with para-tolualdehyde at 50 C for 16 h. 

A side reaction has been identified in the phase transfer catalyzed Wittig reactions. Hydroxide ion attacks positively charged phosphorus to give a phosphine oxide and the methylaromatic hydrocarbon from cleavage of the benzylic carbon-phosphorus bond (Equation 1). The phosphonium ion derived from 9-chloromethy anthracene... 

Reaction between GeF2 and F gives [GeF3]. Several compounds of type MGeCl3 exist where M+ may be an alkali metal ion or a quaternary ammonium or phosphonium ion (e.g. equations 14.56 14.58). Crystal structure determinations for [BzEt3N][GeCl3] (Bz = benzyl) and... 

It is interesting to note that the very widely used Makosza catalyst , benzyl triethyl ammonium chloride, does not show high efficiency in this study. 4) Phosphonium ions are somewhat more effective and thermally stable than the corresponding ammonium catalysts and both are better than arsonium systems. 5) Substitution of the quaternary ion by alkyl rather than aryl groups yields more effective catalysts. 6) Reaction rates are generally greater in orf/io-dichlorobenzene (and presumably in other chlorocarbon media) than in benzene, and botli are better than heptane. In connection with this latter point, Ugelstad and coworkers have studied the reactions of quaternary ammonium phenoxide ions with alkyl halides in a variety of media and concluded that the... 

Stable indefinitely in polymer-bound catalysts under phase transfer conditions that require the presence of hydroxide ion at the ion exchange site. Benzyltrialkylammonium and phosphonium ions are much less stable in base than non-benzylic tetraalkylammonium and phosphonium ions. Industrial applications of polystyrene-supported onium ion catalysts under strongly basic conditions will require catalysts such as 7, 1 rather than the usual commercially available... 

Unexpected cleavage of the benzylic group occurs when Wittig reactions of the sterically hindered phosphonium salts (139) are attempted in DMSO-DMSO systems. This is thought to arise because there is solvolysis of the salts in the medium containing methylsulphinylmethanide ion (Scheme 5). ... 

The reaction is carried out in two steps. First, the phosphonium salt is formed by the reaction of triphenylphosphine with benzyl chloride in Experiment 39A. The reaction is a simple nucleophilic displacement of chloride ion by triphenylphosphine. The salt that is formed is called the "Wittig reagent" or "Wittig salt."... 

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