A-hydroxyphosphine oxides

Trofimov et al. accomplished the addition of bis(phenylethyl)phosphine-oxide and -sulfide to aldehydes and ketones to afford the corresponding a-hydroxyphosphine oxides/sulfides (Scheme 27). ... 

Probably the presence of a second ligating group in the ligand enhances the stability of phosphine oxide-rhodium complexes [177]. Thus, the group of Alper utilized successfully a-hydroxyphosphine oxides, which work, for example, in the reaction of HPPh2 with benzaldehyde (Scheme 2.53) [178], as promoting ligands in the rhodium-catalyzed hydroformylation [179]. 

Scheme 2.53 Preparation of a-hydroxyphosphine oxides (in the paper no information is given as to where the oxygen for the oxidation of the phosphine group comes from).

Sodium iodide acetic acid a-Hydroxyphosphine oxides from 0X0 compds. 

SCHEME 4.131 Microwave-assisted synthesis of a-hydroxyphosphine oxides [226],... 

The electrochemical reduction of mono- and bis(acyl)phosphine oxides was observed to lead to the corresponding radical anions/ In the field of optically active phosphine oxides, the resolution of l-butyl-3-methyl-3-phospholene oxide with TADDOL derivatives was described/ The preparation of the enantiomers of BINAP and its derivatives was summarized in a review/ The deracemization of tert-butyl-phenylphosphine oxide using dibenzoyltartaric acid afforded one enantiomer in a configurationally stable form, in contrast to suggestions in the literature and to general opinion. The enantiomer of the secondary phosphine oxide was utilized in the preparation of a-hydroxyphosphine oxides (Scheme 64). The adducts were obtained in >95% ee and in >95% de. °... 

Fig. 11.11. Wittig-Horner synthesis of stereouniform alkenes via ketophosphine oxide B. The reaction proceeds via its Felkin-Anh-selective or chelate-controlled reduction to form the syn-configured hydroxyphosphine oxides D and the anti-configured hydroxyphosphine oxides E. D and E continue to react—after deprotonation with KO-tert-Bu—via a syn-elimination to give the trans- and cis-alkene, respectively. R1 in the formula A-C corresponds to a primary (prim-alkyl) or a secondary alkyl residue (sec-altyl).

In Homer s original work, phosphine oxides (202) were treated with potassium r-butoxide or sodamide and allowed to react with an aldehyde or ketone to form the alkene (203) directly (Scheme 28). Homer observed that the use of a lithium anion resulted in the isolation of Ae p-hydroxyphosphine oxide (204). In addition, he found that the intermediate hydroxyphosphine oxide could be obtained by LAH reduction of the ketophosphine oxide. Warren and coworkers t ve utilized and expanded upon these techniques by isolating and separating the diastereomeric, frequently crystalline, p-hydroxyphosphine... 

Another variation of the Wittig reaction is the Wittig-Horner reaction, in which the anion generated ot- to phosphine oxide is used as a nucleophile to react with carbonyl compounds. The intermediate formed in this reaction, -hydroxyphosphine oxide, is isolable particularly when bases with lithium counterion are used for deprotonation. Since the j6-hydroxyphosphine oxides are diastereomers, they can be separated and subjected to elimination to form the corresponding alkenes. Since the elimination of phosphonate moiety is syn, stereospecific alkenes are obtained from the elimination step. As expected, the generation of erythro and threo isomers is dependent on the solvent and the reaction conditions. 

Excellent activities in the coupling of all kinds of aryl chlorides were achieved by use of catalyst 13 containing the bulky bis(adamantyl)( -butyl)phosphane. TONS of 10 to 2 X 10 were recorded even for non-activated aryl chlorides [23]. Quite recently, phosphine oxides according to the equilibrium in eq. (4) were used with Pd2(dba)3 in the Suzuki coupling of aryl chlorides, while a hydroxyphosphine complex/Ni(COD)2 catalyzes the Kumada coupling of the same substrates [26],... 

The polarographic reduction of triphenylphosphine oxide and trioctyl-phosphine oxide at low concentration in nitroethane has been studied. The estimation of phosphate insecticides by polarography has been reported, and the rearrangement of a-hydroxyphosphinates has been followed by conductance. ... 

Warren showed that olefination of ketones and aldehydes, or even esters, with phosphine oxide carbanions allows some control of stereochemistry in the alkene products. Reaction with an aldehyde or ketone generates diastereomeric P-hydroxyphosphine oxide products, which can be isolated and then chromatographically separated. Reaction of 573 with n-butyllithium was followed by addition of 3,4-methylenedioxy-benzaldehyde (574, known as piperonal) to give a 9 1 mixture of 575/576, the syn and anti alcohol, respectively.514 7i,e pyre syn alcohol 575 was isolated in 75% yield by chromatography on silica gel. 

A soln. of startg. phosphine imine in THF added dropwise to /-PrjNLi in the same solvent at —30° under argon, the mixture stirred for 1 h, cooled to —70°, treated dropwise with benzaldehyde in THF, then allowed to warm to room temp. - erythro-product. Y 86%. F.e., electrophiles, and conversion to p-hydroxyphosphine oxides, s. J. Barluenga et al.. Synthesis 1988, 562-4. 

Mechanistic investigations have shown that reduction of Ni(II) to Ni(0) and deprotonation of the hydroxyphosphine ligand leads to a nickel-magnesium bimetallic species. Oxidative addition occurs through transition state TS2 wherein the bimetallic species performs a push-pull cooperative activation of the electrophile (Figure 5.2). This activation differs from the one observed when using... 

---