Triphenylphosphine oxide, and the

In summary the Mitsunobu reaction can be described as a condensation of an alcohol 1 and a nucleophile—NuH—11, where the reagent triphenylphosphine is oxidized to triphenylphosphine oxide and the azodicarboxylate reagent 12 is reduced to a hydrazine derivative 13 ... 

The residue is prone to bump during the late stages of the distillation. Wine red splashes on the wall of the distillation head results in contamination of the product with impurities, including triphenylphosphine, triphenylphosphine oxide, and the ruthenium complex. If the product is contaminated with these impurities, it can be redistilled. 

The probable steps of the catalytic reaction have been studied individually. It has been shown that the molybdenum dioxo complex, X, reacts with triphenylphosphine in an inert atmosphere to give triphenylphosphine oxide and the red molybdenum rV complex, [MoO(S2CN(n-Pr)2)2], equation (89), which can be separated by chromatography on AI2O3 in an oxygen free atmosphere. 

FIGURE 16.82 Ylides are nucleophiles and will add to carbonyl compounds to give intermediates that can close to oxaphosphetanes. These four-membered ring compounds can open to give triphenylphosphine oxide and the product alkenes. 

Triphenylphosphine oxide (and PhsAsO or Ph2SeO) are reduced by MesSiNs 19, via the labile diazidophosphines 1780, to triphenylphosphine (triphenylarsine or diphenylselenide), nitrogen, and HMDSO 7, whereas iodosobenzene gives, via 1781, iodobenzene, nitrogen, and HMDSO 7 [30] (Scheme 12.9). 

A. Preparation.—The first reverse Wittig olefin synthesis has been reported. Triphenylphosphine oxide and dicyanoacetylene at 160 °C gave the stable ylide (1 78%) the reaction was reversed at 300 °C. No comparable reaction was observed with a variety of other activated acetylenes but tri phenyl arsine oxide gave the corresponding stable arsoranes with dicyanoacetylene (— 70 °C), methyl propiolate, hexafluorobut-2-yne, dimethyl acetylene dicarboxylate, and ethyl phenylpropiolate (130 °C). 

Early in the last century, the Nobel Prize winning chemist Hermann Staudinger discovered a reaction between phosphines and azides, which became known as the Staudinger reaction (Staudinger and Meyer, 1919). Triphenylphosphine reacts with azides to form an intermediate iminophosphorane with the release of nitrogen gas. This intermediate quickly breaks down in aqueous environments to yield triphenylphosphine oxide and a primary amine (Figure 17.17). 

The amount of molecular sieves 4 A largely influences the product s ee[11]. Usually 100 mg (for the CMHP oxidation) or 1 g (for the TBHP oxidation) of MS 4A for 1 mmol of substrate is enough however, in the case where chemical yield and/or optical yield are not high, use of excess MS 4A often improves them. The addition of achiral ligands such as tributylphosphine oxide, tri-o-tolyl- and tri-/)-tolylphosphine oxides, hexamethylphosphoric triamide, triphenylpho-sphate, lutidine N-oxide, and l,3-dimethyl-2-imidazolidinone were found to be less effective than that of triphenylphosphine oxide in the epoxidation of chalcone. 

The mechanism for the Mori-Ban indole formation is representative of many Pd-catalyzed pyrrole annulation processes [123], Reduction of Pd(OAc)2 by PPh3 generates Pd(0) species accompanied by triphenylphosphine oxide and acetic anhydride. 

Diazo-l,2,3-triazole reacted with triphenyl phosphine in ether to give the ylide 248, which is so unstable it rapidly hydrolizes during filtration to triphenylphosphine oxide and triazole [83DIS(B)(43)2557]. 

These latter two examples add support to the projected mechanism. Other supporting features are that use of perdeuteriomethanol as a solvent for the reaction of (18b) provides the corresponding 6-deuteriodi-hydrodiazepinium salt and that in the protodebromination of (18b) in propan-l-ol, the other expected products, triphenylphosphine oxide and 1-bromopropane, were both isolated and characterized [81AG193, 81AG(E)190]. 

Dehydration of diols to cyclic ethers. The reagent dehydrates a variety of diols to cyclic ethers with formation of triphenylphosphine oxide as the co-product. Yields of cyclic ethers are high from 1,2-, 1,4- and 1,5-diols. Although (Z)-2-butene-1,4-diol is converted into 2,5-dihydrofuran in 95% yield, the (E)-isomer is converted in 35-40% yield into 3,4-epoxy-l-butene.1... 

Trimethylene oxide also reacts rapidly with cobalt hydrocarbonyl and carbon monoxide at 0° C to produce 4-hydroxybutyrylcobalt tetracarbonyl, identified by means of its triphenylphosphine derivative, and the reaction of the tetracarbonyl with dicyclohexylethylamine to produce y-butyrolactone... 

In the presence of triphenylphosphine oxide, and also depending on the nature of the pentahalophenyl group employed, similar synthetic reactions afforded [AuTl(C6F5)2(Ph3P=0)2] and [AuTl(C6Cl5)2(Ph3P=0)2(THF)] with the... 

We have a fairly detailed knowledge of the mechanism of the Wittig reaction (Figure 11.3). It starts with a one-step [2+2]-cycloaddition of the ylide to the aldehyde. This leads to a heterocycle called an oxaphosphetane. The oxaphosphetane decomposes in the second step—which is a one-step [2+2]-cycloreversion—to give triphenylphosphine oxide and an alkene. This decomposition takes place stereoselectively (cf. Figure 4.44) a cw-disubstituted oxaphosphetane reacts exclusively to give a cis-alkene, whereas a fraws-disubstituted oxaphosphetane gives only a trans-alkene. The reaction is stereospecific. 

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