Phosphine oxides metalation

On the synthetic side, single diastereomers of P-keto phosphine oxides have been generated from intermolecular acylation of phosphine oxides using either chiral esters or chiral phosphine oxides. In most cases, reduction of the ketone products was not affected by the presence of extra chiral centres. Addition of metallated phosphine oxides to proline-derived ketoaminals provides a new route to optically active P-hydroxy phosphine oxides. The P-hydroxy phosphine oxide 97 has been prepared by the caesium fluoride mediated reaction of silyl-substituted phosphine oxide 98 and benzaldehyde." The synthesis of two (E)-(6-hydroxy-2-hexen-l-yl)diphenylphosphine oxides (99) has been reported. The Horner-Wittig reactions of these compounds with various carbonyl compounds... 

Wittig-Horner Reactions of Metallated Phosphine Oxide Anions... 

Preparation and Properties of Organophosphines. AUphatic phosphines can be gases, volatile Hquids, or oils. Aromatic phosphines frequentiy are crystalline, although many are oils. Some physical properties are Hsted in Table 14. The most characteristic chemical properties of phosphines include their susceptabiUty to oxidation and their nucleophilicity. The most common derivatives of the phosphines include halophosphines, phosphine oxides, metal complexes of phosphines, and phosphonium salts. Phosphines are also raw materials in the preparation of derivatives, ie, derivatives of the isomers phosphinic acid, HP(OH)2, and phosphonous acid, H2P(=0)0H. 

Addition of Metalated Allylic Phosphine Oxides, Phosphonates, Sulfones, and Sulfoxides and Sulfoximines to a,/i-l nsaturated Carbonyl Compounds... 

Metalated Allylic Phosphine Oxides and Phosphonates Simple Diastcreoselection... 

The reaction was carried out analogously to the general procedure for the addition of metalated ally 1 sulfoxides given in Section 1.5.2.2.3.2. BuL.i is used, in this case, for deprotonation instead of LDA. BuLi is added to a solution of 1 - 3 mmol of the phosphine oxide or phosphonate in THF until the first permanent appearance of the red color of the anion. Thereupon, 1.1 equivalents of the BuLi is added. For the phosphonates, whose anions are less intensely colored, 1.1 equivalents of BuLi are added to the solutions after the first permanent appearance of the red color of an added indicator, 2.2 -bipyridyl. 

Various phosphines are valuable ligands for metal centers involved in catalytic and noncatalytic organometallic chemistry. Unfortunately, phosphines are readily oxidized to phosphine oxides and to prevent their oxidation they... 

B. From Metallated Phosphines.—Lithium diphenylphosphide and ethylene oxide produce (7), which when added to chlorodibutyl- or chlorodiphenyl-phosphine yields 2-diphenylphosphinoethyl phosphinites (8). 

A catalytic cycle proposed for the metal-phosphine complexes involves the oxidative addition of borane to a low-valent metal yielding a boryl complex (35), the coordination of alkene to the vacant orbital of the metal or by displacing a phosphine ligand (35 —> 36) leads to the insertion of the double bond into the M-H bond (36 —> 37) and finally the reductive elimination to afford a hydroboration product (Scheme 1-11) [1]. A variety of transition metal-boryl complexes have been synthesized via oxidative addition of the B-H bond to low-valent metals to investigate their role in cat-... 

As in the P(III) chemistry above, both late metal (Pd) and lanthanide catalysts have been used for P(V)-H additions to alkynes, alkenes, aldehydes, and imines. In addition, titanium, aluminum, and zinc catalysts have been employed. Typical P(V) substrates include dialkyl phosphites P(0R)2(0)H and phosphine oxides PR2(0)H. 

The discussion of the activation of bonds containing a group 15 element is continued in chapter five. D.K. Wicht and D.S. Glueck discuss the addition of phosphines, R2P-H, phosphites, (R0)2P(=0)H, and phosphine oxides R2P(=0)H to unsaturated substrates. Although the addition of P-H bonds can be sometimes achieved directly, the transition metal-catalyzed reaction is usually faster and may proceed with a different stereochemistry. As in hydrosilylations, palladium and platinum complexes are frequently employed as catalyst precursors for P-H additions to unsaturated hydrocarbons, but (chiral) lanthanide complexes were used with great success for the (enantioselective) addition to heteropolar double bond systems, such as aldehydes and imines whereby pharmaceutically valuable a-hydroxy or a-amino phosphonates were obtained efficiently. 

Polymeric or monomeric complexes are formed in the reaction between zinc halides and dimethyl(aminomethyl)phosphine oxide dependent on the ratio of reactants. The ligand can bind as bidentate to one metal center or bridge two metal centers through the amine N and phosphine oxide O atoms.851... 

We successfully developed combinatorial approaches for the discovery of industrial ligands and/or catalysts [Scheme l].1 Air-stable phosphine oxides with formal valence five in the presence of transition metals undergo tautomerization to the less stable phosphinous acids, which subsequently and... 

Many of the reagents developed initially for the recovery of base or radioactive metals have also been investigated as potential PGM extractants, e.g., phosphine oxides,310-313 dialkylsulfoxides,314 dialkyl-and diphemd-thioureas,296,315-317 thiopicolinamides, thiobenzanilide,319 phosphate diesters,320 tetra-... 

Hydroxymethyl phosphines are susceptible to oxidation to form the phosphine oxide derivative. Therefore, avoid excess oxygen, oxidizing agents, or azide compounds, which react with phosphines in the Staudinger reaction (Chapter 17, Section 5). In addition, metallic surfaces can be modified via the phosphine group to result in hydroxymethyl group substitutions. 

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