Phosphonium fluorides

These quaternary phosphonium fluorides provide a range of activities for the displacement of halogen by fluorine [30] (Table 3)... 

When phosphonium fluorides are used, no base is necessary, as these react directly with the substrate to give the alkene Schiemenz, G.P. Becker, J. Stdckigt, J. Chem. Ber, 1970, 103, 2077. 

Phosphonium fluorides have been used in olefin synthesis without additional base, the fluoride anion being sufficiently strong a base to remove the ct-proton from the salts (2 R = Ar or COR ) in acetonitrile. 

Wittig reactions of phosphonium fluorides in dipolar non-HBD solvents can be carried out without an additional base e.g. 4-nitrobenzaldehyde reacts slowly with (4-nitrobenzyl)triphenylphosphonium fluoride in refluxing acetonitrile to give 4,4 -nitro-stilbene in good yield (84 cmol/mol) [642], In this reaction, the fluoride ion attacks its own cation to give the corresponding Wittig ylide as intermediate. 

Alkyl fluorides can be prepared by heating alkoxytris(dimethylamino)phosphonium fluorides. For example, 3-fluoro-2-phcnylpropan-1-ol (4) was obtained in 57% yield from the corresponding salt. ... 

Another ylide synthesis avoiding basic conditions starts from phosphonium fluorides. " Fluoride ions are basic enough to play the role of the usually added external base, giving rise to the formation of a phosphonium salt/ylide equilibrium (equation 16). 

An industrially important application of the lipophilic tetrakis(dimethylamino) phosphonium fluoride is as a phase-transfer catalyst in the Halex process for technical synthesis of fluoroarenes. 

The phosphonium fluoride (46) is the first example of a phosphonium salt that contains an ionic fluoride. The compound has considerable potential as a fluorinating reagent... 

The fluoride ion in the tetraaza analogue of the fenestrane related phosphonium fluoride (158) is an example of a completely ionic fluoride ion <81JA5265>. The ozonide (159) from an adamantyl type phosphite is a good water soluble source of singlet oxygen and is 1.4 times more stable than ozonide (160) <75JOCll85>. 

Olefins have been obtained in a stereoselective manner via the Wittig procedure. The ylid-carbonyl adduct is treated with a strong base and an electrophile (Mel, PhCHO) to form olefins of predictable stereochemistry. The Wittig reaction has also been reported to occur with phosphonium fluorides in the absence of base. ... 

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