Reaction with phosphine oxides

Armstrong, D. R., Barr, D., Davidson, M. G., Hutton, G., O Brien, P., Snaith, R., Warren, S. Experimental and molecular orbital calculational study of the stereoselective Horner-Wittig reaction with phosphine oxides control of stereoselectivity by lithium. J. Organomet. Chem. 1997, 529, 29-33. 

The Horner-Wittig reaction with phosphine oxides The Peterson reaction... 

A variation of the Wittig reaction that can overcome problems with the stereochemical outcome is the Homer-Wittig reaction with phosphine oxides. The oxides are obtained by quatemization of triphenylphosphine and hydrolysis of the phosphonium salt, or by reaction of hthiodiphenylphosphide with an alkyl halide or sulfonate and oxidation of the resulting phosphine with hydrogen peroxide. The derived hthio species react with aldehydes or ketones to give p-hydroxy phosphine oxides, which ehminate on treatment with a base such as sodium hydride or potassium hydroxide to form the alkene. In common with the Homer-Wadsworth-Emmons reaction, the phosphorus by-product is water soluble and easily removed from the product. 

Reaction with Phosphine Oxides. Phosphine oxides react with TMS-I to form stable adducts (eq 36). These 0-silylated products can undergo further thermolytic reactions such as alkyl group cleavage. 

The reaction with sodium sulfite or bisulfite (5,11) to yield sodium-P-sulfopropionamide [19298-89-6] (C3H7N04S-Na) is very useful since it can be used as a scavenger for acrylamide monomer. The reaction proceeds very rapidly even at room temperature, and the product has low toxicity. Reactions with phosphines and phosphine oxides have been studied (12), and the products are potentially useful because of thek fire retardant properties. Reactions with sulfide and dithiocarbamates proceed readily but have no appHcations (5). However, the reaction with mercaptide ions has been used for analytical purposes (13)). Water reacts with the amide group (5) to form hydrolysis products, and other hydroxy compounds, such as alcohols and phenols, react readily to form ether compounds. Primary aUphatic alcohols are the most reactive and the reactions are compHcated by partial hydrolysis of the amide groups by any water present. 

The reduction of optically active methylphenyl-n-propylphosphine sulphide with lithium aluminium hydride proceeds with 100% retention, whereas the reaction of phosphine oxides with lithium aluminium hydride leads to racemization. ... 

B. Electrophilic Reactions of the P=0 and P=S Groups. Hydrolysis studies with phosphine oxides continue to reveal problems associated with the role of pseudorotational processes in determining mechanism. The failure of benzyldiphenylphosphine oxide (36) to exchange when hydrolysed in under bimolecular conditions has been reported. ... 

Two contrasting conclusions have been reported in the reactions of lithium aluminium hydride in THF with phosphine oxides and phosphine sulphides respectively. The secondary oxide, phenyl-a-phenylethylphos-phine oxide (42), has been found to be racemized very rapidly by lithium aluminium hydride, and this observation casts some doubt on earlier reports of the preparation of optically active secondary oxides by reduction of menthyl phosphinates with this reagent. A similar study of the treatment of (/ )-(+ )-methyl-n-propylphenylphosphine sulphide (43) with lithium aluminium hydride has revealed no racemization. These results have been rationalized on the basis of the preferred site of attack of hydride on the complexed intermediate (44), which, in the case of phosphine oxides (X = O), is at phosphorus, and in the case of the sulphides (X = S), is at sulphur. Such behaviour is comparable to that observed during the reduction of phosphine oxides and sulphides with hexachlorodisilane. ... 

Compared with the variety of existing carbon or nitrogen nucleophiles that were subjected to nucleophilic addition to there are few examples for phosphorus nucleophiles. Neutral trialkylphosphines turn out to be to less reactive for an effective addihon to Cjq even at elevated temperatures [114], Trialkylphosphine oxides show an increased reactivity. They form stable fullerene-substituted phosphine oxides [115] it is not yet clear if the reaction proceeds via a nucleophilic mechanism or a cycloaddition mechanism. Phosphine oxide addition takes place in refluxing toluene [115], At room temperature the charge-transfer complexes of with phosphine oxides such as tri-n-octylphosphine oxide or tri-n-butylphosphine oxide are verifiable and stable in soluhon [116],... 

Diphenylphosphine oxide reacts with diethyl acetylenedicarboxylate to give a 2 1 adduct (460), and it has been suggested that in this reaction the phosphine oxide reacts in the tervalent form [Eq. (68)]. On the... 

Pentadecacarbonylpentaruthenium carbide oxidative addition reactions, 30 206 reaction with phosphines and diphosphines, 30 191... 

Iodide-promoted reactions in phosphine oxide solvents have been observed under some conditions to produce ethanol from H2/CO with good rates and high selectivities (193-195) (Table XVI, Expts. 1-3). Experimental evidence suggests that the ethanol is a secondary product, although its selectivity is high even after very short reaction times (193). An acid component is believed to be involved in alcohol homologation by this system, which will be described in more detail below. 

Primary and secondary phosphines may be readily alkylated with alkyl halides simply by nucleophilic displacement of halide by a phosphine anion (equation 50)84,392. With primary phosphines, dialkylation is readily achieved if excess base is used. Alkyl halides will also react with phosphine oxide and other phosphorous anions, especially if the reaction is performed under PTC392"395. 

Other ligands have been synthesized more recently utilizing the same synthetic and theoretical philosophy.52,53 A chiral ditosylate or dimesylate is generally reacted with a metal phosphide to produce the diphosphine ligand. There have been problems with these displacement reactions with secondary ditosylates as has been discussed earlier. More recent procedures report success with phosphine oxide or borane anions. 

The reaction is carried out in a non-polar solvent like propanone precipitated caesium nitrate is filtered off and green (the most characteristic colour of complexes) crystals of the nitrate complex are obtained on concentrating the solution. U(N03)4(OPPh3)2 has a 10-coordinate structure (Figure 11.7) with phosphine oxide ligands trans to each other, and bidentate nitrates. 

The elimination step is stereospecific thus, eryfhro-P-hydroxy phosphineoxide, obtained by the reaction of benzaldehyde with phosphine oxide, gives Z-isomer and threo-isomer gives E-isomer (Scheme 4.27). 

Ignition on contact with bromine pentafluoride (or violent reaction), chlorine trifluoride, fluorine, metals (powdered) + water, aluminum-titanium alloys + heat, metal acetylides (e.g., cesium acetylide, copper(I) acetylide, lithium acetylide, mbidium acetylide), nonmetals (e.g., boron ignites at 700°C), phosphoms, sodium phosphinate. Violent reaction with acetaldehyde, aluminum + diethyl ether, dipropylmercury, titanium (above 113°C). Incandescent reaction with cesium oxide... 

Reaction with phosphine in alkaline solution also has kinetics which make it probable that hypochlorous acid is the active oxidant . The overall reaction, viz. 

One of the earliest chemical transformations of 1,2-dioxetanes was their reaction with phosphines (Eq. 72). It was shown that the trivalent phosphorus first inserts into the peroxide bond to afford a relatively stable phosphorane. On warming the phosphorane eliminates phosphine oxide to yield the epoxide product. In this elimination, there is inversion of the stereochemistry at one of the carbon centers. 

Phosphine oxides. The complex [U(OTf)2(OPPh3)4][OTf] (OTf = triflate) has been prepared by the reaction of U(OTf)3 with phosphine oxide. One of the inner sphere triflate ligands is monodentate, and the other is bidentate, supporting an overall pentagonal bipyramidal coordination environment about the uranium center. ... 

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