Phosphines hydroxyphosphinic acids

New y-ethoxycarbonyl- and ot-amino-alkyl-hydroxyphosphinic acid derivatives (366) and (367) were conveniently prepared by Michael addition or Kabachnik-Fields reaction of a new precursor, benzyloxymethyl hydrogen-phosphinate (368), with a,p-unsaturated esters or imines (Scheme 94). " Phosphinic acid inhibitors (369) of Cathepsin C were synthesized by addition of methyl acrylate to the appropriate a-amino phosphinic acid and by... 

Trans-tSksaes can be synthesized by the Homer reaction from the ketophosphine oxide, which is reduced selectively to the threo adduct. This inteimediate is typically foimed by reaction of the phosphine oxide widi an ester or acid chloride. Alternatively, the keto intermediate may be obtained by oxidation of -hydroxyphosphine oxides. This sequence was applied to the synthesis of the pure ( )-triene (237) by Warren (equation 57). ... 

It should be finally noted that hydroxyphosphines can be converted under very smooth conditions into sulfonated phosphines by acylation with o-sulfobenzoic anhydride, as shown by Borner et al. (Eq. 5) [26]. With this methodology in hand the severe conditions commonly used for the incorporation of sulphonate groups in phosphines can be avoided. Acid-labile functional groups like acetals survive under these conditions. In comparison to the parent hydroxyphosphines the water solubility of the relevant Rh catalysts was strongly enhanced [27]. In the asymmetric hydrogenation of prochiral olefins, moderate enantioselectivities were achieved. 

The desired acids 31 were obtained by simply bubbling CO2 through a solution of the deprotonated phosphine boranes 4 and could be quantitatively reduced to (3-hydroxyphosphines 32. The hydroxyl group of 32 was then mesylated or tosylated in good yields to alford compounds 33, which were employed to prepare other compounds like P/N and P/S bidentate ligands (see later in this section) and unsymmetric BisP ligands (Section 5.2.1.3). The yields of compounds 31-33 are listed in Table 5.7. 

NMR spectroscopy was applied in the enantiomeric excess determination of (iV,iV-dimethyl-(2,2,2-trifluoro-l-phenylethyl)amine-C,A)palladium complexes of a-amino acids.Dunina et al. used NMR spectroscopy and a P -chiral phosphapalladacycle for the enantiomeric purity determination of a-amino acids. P NMR spectroscopy was also used in the enantiomeric excess determination of N,C o///5< -palladated complexes of P-chiral phosphines. A ferrocene-based reagent (i p,successfully designed for the chiral recognition of /3-hydroxyphosphines and the discrimination of ( )-bis(diphenylphosphino)-1,1 -binaphthyl. 

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. °... 

---