Phosphines, chiral also

Alternative methods of preparation of chiral phosphinates have also been reported... 

More complex chiral phosphines have also been prepared, for example, (24). ... 

Chiral-sulfonated phosphines have also been synthesized and used in the preparation of water-soluble late transition-metal complexes. These complexes, like their analogs in nonaqueous solution, can be used as homogeneous catalysts for the hydrogenation of prochiral alkenes. When the phosphine ligand has a chiral center, the alkane product can potentially be obtained in enantiomeric excess. A variety of different approaches have been used to prepare chiral phosphines that are soluble in aqueous... 

BINAP is a new type of fully aryl-substituted dlphosphine with only an axial element of chirality. Optically pure BINAP was first synthesized by the optical resolution of (l)-BINAP using optically active d1-iJ-chlorob1s[(S)-N,N-dimethyl-a-phenylethylam1ne-2C,N]d1pallad1um. The phosphine Is also obtained by stereospecific transformation of optically active 2,2 -d1bromo-l,l -binaphthyl The procedure outlined here, however, is the best preparative-... 

An additional access to chiral sulfonated phosphines was also described [13a,b]. The method is based on the acylation of chiral hydroxyphosphines with commercial o-sulfobenzoic anhydride and was demonstrated on a number of diphosphines based on the DIOP skeleton (Eq. 1). The chelating properties of the diphosphines were studied by preparation of cationic rhodium complexes. The presence of the o-sulfobenzoate group is thought not to influence the catalytic properties. Chiral phosphines containing a sulfonate group (e.g., 8) were also obtained from BPPM by acylation with trimellitic anhydride followed by treatment with sodium tauri-nate [13 c],... 

Enantioselective hydrogenation of prochiral olefins such as conjugated acids or enamides (also asymmetric hydroboration) with chiral Rh phosphine catalysts (also Ti-catalysts)9 (see 1st edition). 

Rh(diPAMP)(A )], Ac = acylaminocinnamic acid, could be monitored and bond lengths determined. In the adduct there was clear evidence of coordination to both the C-C double bond and a carbonyl oxygen. Monitoring a similar sequence for derivatives of the chiral monodentate phosphine, CAMP, also provided evidence for the solvated analogue, [Rh(CAMP)2(MeOH)2) but attempts to fit the data In the presence of the catalyst substrate were unsuccessful, apparently indicating a mixture of solution species. 

Other P-Phos related ligands, such as the chiral 4-bis(tolylphosphino) (Tol-P-Phos) and chiral 4-bis(cyclohexylphosphino) (Cy-P-Phos) ligands, were prepared and purified in a similar, or slightly modified, manner using the appropriate phosphines. They also form mthenium complexes that have related catalytic activities [Wu Chan Acc Chem Res 39 711 2005, Au-Yeung Chan Coordination Chemistry Reviews 248 2151 2004],... 

As for other catalysts, chiral Rh(III) porphyrin catalysts 23a were also foiuid to catalyze asymmetric cyclopropanation of alkenes with EDA (84). Although moderate enantiocontrol (<60% ee) was observed, the reaction was cis-selective tic = 1 2.5) with >1800 turnover number. Other newly developed Rh(III) porphyrin catalysts 23b gave slightly improved enantioselectivity (68% ee) with moderate diastereoselectivity (85). Similar to their achiral covmterparts, a perpendicular approach of alkene to rhodium-carbene was proposed as a mechanism. Apart from porphyrins, phosphine catalysts also gave interesting results. Catalyst 24, which contains backbone chirality, catalyzed the cyclopropanation of styrene with EDA to give 91% ee for the cis-isomer and 90 10 of the cis trans ratio (86). 

Phosphorus, in the same family as nitrogen, forms trivalent compounds called phosphines, which also have trigonal pyramidal geometry. The activation energy for pyramidal inversion of trivalent phosphorus compounds is considerably greater than it is for trivalent compounds of nitrogen, with the result that a number of chiral phosphines have been resolved. 

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