Phosphorus compounds chiral

Although unsynunetrically substituted amines are chiral, the configuration is not stable because of rapid inversion at nitrogen. The activation energy for pyramidal inversion at phosphorus is much higher than at nitrogen, and many optically active phosphines have been prepared. The barrier to inversion is usually in the range of 30-3S kcal/mol so that enantiomerically pure phosphines are stable at room temperature but racemize by inversion at elevated tempeiatuies. Asymmetrically substituted tetracoordinate phosphorus compounds such as phosphonium salts and phosphine oxides are also chiral. Scheme 2.1 includes some examples of chiral phosphorus compounds. 

Chiral Phosphorus Compounds Koizumi et al. 251 have prepared a series of chiral organophosphorus compounds (256) in which the phosphorus atom is the asymmetric center, whereby amino acid derivatives were used as chiral auxiliary reagents. 

For a review of chiral phosphorus compounds, see Valentine, in Morrison. Ref. 88, vol. 4, pp. 263-312. Horner Fuchs Tetrahedron Lett. 1962, 203. 

Among the preparative methods used for obtaining P-chiral phosphorus compounds, there are procedures involving the use of optically pure auxiliaries like (—)-menthol [40], (—)-ephedrin [41,42], or more recently, the kinetic resolution of 1-hydroxymethylalkylphenylphosphine oxides using Pseudomonas or Candida antarctica lipases [43], It has been found that some [(alkyl-substituted)arene] phosphinates and phosphine oxides can also be resolved efficiently by inclusion complexation with optically active 2,2 -dihydroxy-1, 1 -binaphthyl (17) [44],... 

Yang GC, Xu Y, Hou JB et al (2010) Determination of the absolute configuration of pentacoordinate chiral phosphorus compounds in solution by using vibrational circular dichroism spectroscopy and density functional theory. Chem Eur J 16 2518-2527... 

Studies of the asymmetric synthesis of chiral phosphorus compounds, (100) via the destructive-selective oxidation of (99) with various camphor derived oxaziridines has been described (91CB1627). The des were mostly modest, for example 8-48%. 

The cis/trans stereochemistry of a series of trivalent amino acid derived chiral phosphorus compounds has been established on the basis of Jhp couplings all of the cis isomers exhibited for the ring hydrogen Vhp = 3.4-3.T Hz while all of the trans isomers revealed Vhp = 1.4-1.8 Hz. It should be mentioned that the... 

Juge developed a powerful method (Juge-Stephan method) [1, 51] for the preparation of / -stereogenic phosphines based on the use of ephedrine as a chiral auxiliary. The key reactants in this methodology are 1,3,2-oxazaphospholidine boranes 78, prepared by a one-pot reaction from bis(diethylamino)phenylphosphine and (—)-ephedrine, followed by protection with BH3. The cyclization of the (—)-ephedrine takes place stereoselectively, with preferential formation of the (/ p)-diastereoisomer in 90% de [52, 53]. The absolute configuration at the phosphorus atom has been determined by chemical correlations and NMR analysis, and proved by X-ray analysis [54]. Oxazaphospholidines react readily with electrophiles or nucleophiles to provide various chiral phosphorus compounds. Enantiomeric antipodes of tertiary phosphines (Sp)-79 and (Rp)-81 were obtained from (-1-)- or (-)-ephedrine, as shown in Scheme 25. The configuration at the E-atom is controlled by the configuration at the Ph-substituted Cj of (-i-)-pseudoephedrine or ( )-ephedrine, respectively. This was confirmed by X-ray crystal-structure analyses of two intermediate compounds in the synthetic route to the chiral triarylborane-phosphine adducts [54]. 

The chlorophosphine boranes 97 are efficient starting reagents for the synthesis of various classes of P-chiral phosphorus compounds. Reactions of chlorophosphine boranes 97 with nucleophiles, such as carbanions, phenoxides, phenylthiolates, or amides, leads to the formation of corresponding organophos-phorus compounds 100-103 in yields of 53-99% and with up to 99% ee. This method was also used for the preparation of various classes of symmetric and asymmetric P-chiral ligands useful for asymmetric reactions, catalyzed by complexes of transition metals (Scheme 31) [52, 60, 61]. 

Kolodiazhnyi OI (2012) Recent developments in the asymmetric synthesis of P-chiral phosphorus compounds. Tetrahedron Asymmetry 23 1 6... 

Yang G, Xu Y, Hou J, Zhang H, Zhao Y (2010) Diastereomers of the pentacoordinate chiral phosphorus compounds in solution absolute configurations and predominant conformations. Dalton Trans 39 6953-6959... 

As well as illustrating the synthesis of chiral phosphines this sequence introduces two other types of chiral phosphorus compound the phosphinate ester (36) and the phosphine oxide (37). In fact any tetracoordinate phosphorus compound with four different groups attached to the tetrahedral centre is chiral. The chiral compounds of phosphorus have been reviewed,... 

Although these new chiral phosphorus compounds appear to be interesting ligands, they are not very reactive towards nucleophilic attack by alcohols or amines...did not react in benzene-d (not even at elevated temperatures) with amines or alcohols or water as solvent ... 

Organic phosphorus compounds play an important role in biological systems. In chemical investigations, chiral phosphorus compounds have found extensive applications as chiral ligands occurring in many catalysts used in asymmetric syntheses [77,78]. 

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