Phosphonium anhydrides

Direct Borohydride Reduction of Alcohols to Alkanes with Phosphonium Anhydride Activation N-Proovlbenzene. To a solution of 5.56 g (20 mmol) of triphenylphosphine oxide in 30mL of dry methylene chloride at CfC was added dropwise a solution of 1.57 mL (10 mmol) of triflic anhydride in 30mL of dry methylene chloride. After 15 min when the precipitate appeared, a solution of 1.36g (10 mmol) of 3-phenyl-1-propanol in 10 mL of dry methylene chloride was added and the precipitate vanished in 5 min. An amount of 1.5g (40 mmol) of sodium borohydride was added as a solid all at once and the slurry was stirred at room temperature for... 

Indoxyls and their analogues. Indoxyls and their oxygen and sulfur analogues 65 (Z = NH, O, S) are prepared by the cyclization of anilino-, phenoxy-, and phenylthio-acetic acids 64, respectively, with phosphonium anhydride <1989JOC1144> (for Z = NH), P205 (for Z = 0), and H2S04 (for Z = S) (Scheme 39). 

Recently, some modified reaction conditions have been proposed to improve yields, particularly for aromatic carboxylic acids. A phosphonium anhydride reagent (11) made from triphenylphosphine oxide and triflic anhydride appears to induce reaction at low temperatures in common solvents giving high yields of 2-arylbenzi midazoles in 30-60 min at room temperature (Scheme 3.1.12) [78]. 

Tris(dimethylaniino)phosphonium anhydride bis(tetrafluoroborate) (Bate s reagent)... 

The Initiation Mechanism with Phosphonium Compounds. Although further experimental data are needed to give a fuller understanding of the reaction mechanisms involved in the latent acceleration effect of these quaternary phosphonium compounds in epoxyanhydride resins, there is definite indication, at this stage, that the mechanism does not involve the decomposition of the phosphonium compound to the free phosphine species (16). The initiation mechanism probably involves the formation of hydrogen-bonded phosphonium-epoxy or phosphonium-anhydride complexes which rearrange on the application of heat to form activated species resulting in polymerization of the epoxy-anhydride components ( > ... 

In situ production of triphenyl phosphonium anhydrides as triflate salts 25 (Scheme 2.14) is claimed to be the crucial step for the cycloacylation of arylalkanoic adds in the presence of triphenyl phosphine oxide and triflic anhydride. The reaction proceeds in satisfactory to high yields under mild conditions. Compounds 25 are commonly used directly in situ owing to their very hygroscopic nature and are produced by reaction... 

Some recent highlights include adaptation of Katritzky s benzo-triazole syntheses to ether preparation , generation of acyl radicals by carbonylation , and oxidative ring closures with Fe(C104)3 (as an alternative to the harsher Mn(III) route) . Bis(phosphonium) anhydrides are finding diverse applications, and a number of new vanadium reagents have materialized, e.g. a V(II) complex dimer for cross-coupling of aldehydes as an alternative to the McMurry route . ... 

Phenylbutyric acid added to the phosphonium anhydride (prepared according to Synth. Meth. 44, 166), the mixture warmed to room temp., and stirred for 4h -> a-tetralone. Y 93%. The method is generally milder and cleaner than the polyphos-phoric acid procedure, and without the problems of solubility, viscosity, and work-up. Intermolecular acylation failed. F.e.s. J.B. Hendrickson, M.S. Hussoin, J. Org. Chem. 54, 1144 9 (1989). 

A soln. of triflic anhydride in 1,2-dichloroethane added dropwise to a soln. of Ph3PO in the same solvent at 0°, after 15 min., when the phosphonium anhydride (cf. Synth. Meth. 44, 166) had precipitated, a soln. of ethyl benzoylacetate in 1,2-di-chloroethane added slowly, followed directly by EtjN, and the soln. refluxed for 1 h - ethyl 3-phenylpropynoate. Y 98%. The method was only applied to activated ketones (e.g. 3-dicarbonyl compds.). It is easy, the intermediate enol deriv. does not require isolation, and work-up is simple. F.e.s. J.B. Hendrickson, M.S. Hussoin, Synthesis 1989, 217-8. 

Triphenylphosphine oxidejtrifluoromethanesulfonic anhydridejtriethylamine Phosphonium anhydrides as dehydrating agents... 

Diphosphine monoxides Phosphinous anhydrides Diphosphoxanes 20 Phosphonium anhydrides... 

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