Water-soluble phosphonium salts

Recently, water-soluble phosphonium salts were synthesized and their Wittig reactions with substituted benzaldehydes were carried out in aqueous sodium hydroxide solution (Eq. 8.114).309... 

Water-soluble phosphines, such as 3,3, 3"-phosphanetriyltris(benzenesul-fonic acid) (TPPTS) or m-monosulfonate, give quantitatively the water-soluble phosphonium salts when reacted with a,p-unsaturated acids in water (Larpent and Patin, 1988). They also react with activated alkynes, affording vinylphosphonium salts, vinylphosphine oxides or alkenes depending on the pH of the aqueous solution (Larpent et ai, 1990). 

In an attempt to improve the environmental credentials of Wittig olefination, Russell and Warren have described the synthesis of a range of water/ aqueous base soluble phosphonium salts (67-71) and assessed their reactivity towards carbonyl compounds. The use of D2O as a solvent for the reaction between stable ylides and carbonyl compounds leads to a-deuterated a, 3-unsaturated carbonyl compounds. 

The term phase transfer catalysis was coined by Starks to describe the mechanism of catalysis of reactions between water-soluble inorganic salts and water-insoluble organic substrates by lipophilic quaternary ammonium and phosphonium ions Ql). His investigations of nucleophilic displacement reactions, such as that of aqueous sodium cyanide with 1-chlorooctane, and the investigations of Makosza on reactions of aqueous sodium hydroxide with chloroform to generate dichlorocarbene, and with active ketones and nitriles to generate carbanions, pioneered the field in the mid-1960 s. It was nearly fifteen years before many such processes were adopted in industry. Starks now estimates there are about sixty phase transfer catalytic processes in use worldwide, mostly in pharmaceutical and fine chemical manufacturing (32V... 

Polymer phase-transfer catalysts (also referred to as triphase catalysts) are useful in bringing about reaction between a water-soluble reactant and a water-insoluble reactant [Akelah and Sherrington, 1983 Ford and Tomoi, 1984 Regen, 1979 Tomoi and Ford, 1988], Polymer phase transfer catalysts (usually insoluble) act as the meeting place for two immiscible reactants. For example, the reaction between sodium cyanide (aqueous phase) and 1-bromooctane (organic phase) proceeds at an accelerated rate in the presence of polymeric quaternary ammonium salts such as XXXIX [Regen, 1975, 1976]. Besides the ammonium salts, polymeric phosphonium salts, crown ethers and cryptates, polyethylene oxide), and quaternized polyethylenimine have been studied as phase-transfer catalysts [Hirao et al., 1978 Ishiwatari et al., 1980 Molinari et al., 1977 Tundo, 1978]. 

This method, sometimes called the Horner-Emmons, Wadsworth-Emmons, or Wittig-Hor-ner reaction,658 has several advantages over the use of phosphoranes.659 These ylides are more reactive than the corresponding phosphoranes, and when R is an electron-withdrawing group, these compounds often react with ketones that are inert to phosphoranes. In addition, the phosphorus product is a phosphate ester and hence soluble in water, unlike PhjPO, which makes it easy to separate it from the olefin product. Phosphonates are also cheaper than phosphonium salts and can easily be prepared by the Arbuzov reaction ... 

The ammonium salts, phosphonium salts, iodonium salts, and other organic derivatives are easily prepared from the lactone by neutralization with the appropriate Lewis base. These organic ion salts are relatively easy to purify though they are not—for the most part—soluble in water. 

The process reported here uses a clever combination of the factors that promote catalyst life and efficiency. The soluble phosphine or its phosphonium salt, used in a molar excess of about 50 over palladium, stabilizes the palladium complex in aqueous solution the sulfolane-water solution ensures the solubility of the reactants, while extraction with hexane under CO2 pressure recovers the product with only small contamination by palladium, phosphorus or nitrogen. The phosphine or its phosphonium salt and the ammonium bicarbonate remain in the aqueous solution. Since the TON is good and the solution can be recycled, consumption of palladium is very low. 

Because these fire-retardant salts are water-soluble and subject to leaching, several new methods have been developed which provide a water-resistant or permanent treatment for cotton fabrics and cellu-losic materials. Perkin developed a process involving successive treatment with sodium stannate and ammonium sulfate, which precipitates stannic oxide in the cellulose libers. Antimony oxide in combination with vinyl chloride or other chlorinated polymers has also been found effective. A more recent approach to this problem involves application of fire-retardant resin-forming or cross-linking compounds. " These include materials and methods based on the copolymerization of tetrakis(hydroxymethyl)phosphonium chloride and methylol — melamine, the reaction of bromoform and triallyl phosphate to form a cross-linked polymer, and the cross-linking reaction of tris(l-aziridinyl)phosphine oxide with cellulose, or its copolymerization with tetrakis(hydroxymethyl)phosphonium chloride and other materials. ... 

The incorporation of an alkylammonium group can readily be achieved, as for (128), by reduction of the protected tertiary phosphine (as its oxide) with HSiCl3.251 The analogous phosphonium salt (129) is also known.2 2 The chiral quaternized phosphine (130) has been documented,253 whilst protonation of the rhodium(I) complex containing (131) with aqueous HBF4 gave a water-soluble complex.254 Addition of a weak base (NEt3) cleanly reversed this reaction. 

A number of main group and transition metal dithiocarboxylates have been described. They are commonly prepared by metathesis between alkali metal dithiocarboxylates and metal halides. Heavy metal derivatives usually precipitate from aqueous solutions, but are soluble in organic solvents and can be solvent extracted. The alkali metal, ammonium, phosphonium, and arsonium salts are water soluble.300 The composition of metal complexes is sensitive to preparation conditions and is frequently pH dependent. 

The carbodiphosphorane (3) was unexpectedly obtained when the salt (4) was treated with methylenetrimethylphosphorane, presumably by rearrangement of the initially formed ylide. The phosphonium chloride (5) can be readily dechlorinated with HMPT to give bis(triphenylphosphoranylidene)methane. A similar reaction with salt (6) gave an ylide which is thermally unstable and which dimerizes to give a water-soluble high-melting solid (7) that displays no ylide reactions. ... 

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