Bisphosphines containing

Fig. 41.8 Rh-complex with a bisphosphine-containing cation as ligand.

Lee et al. [103] synthesized a chiral Rh-complex with a bisphosphine-contain-ing cation as ligand (Fig. 41.8, 2) to improve the immobilization of the transition-metal complex within the ionic liquid. 

A chiral bisphosphine containing two ferrocene moleeules has been prepared using Ugi s lithiation as a key step (Scheme 2-9) [20]. Thus, the diphenylphosphinyl group is introduced at the ferrocenylmethyl position of the iodide obtained from lithiated ferrocene 2. Oxidative coupling of the iodoferrocene followed by reduction of the phosphine oxide gives the bisferrocene-bisphosphine 15. The bisphosphine is unique in that a tra j-chelate is formed on its coordination to a metal. 

The Wittig-Horner procedure, starting from bisphosphonate or aromatic bisphosphine oxide monomers, allows for AA/BB-coupling of the PO-activated bismethylene monomers, not only with aromatic dialdehydes but also with aromatic diketones to the corresponding PPV derivatives (76), and for the selfcondensation of AB-type aromatic starting compounds containing both alde-hyde/keto and PO-activated methylene functions [101]. 

To demonstrate his point, Sarafidis has shown that the catalyst system containing trisphosphine (71) 35 as ligand is just as effective as the one containing two bisphosphines. 

The seven-membered ring containing chiral bisphosphine 121 (n = 1) was made as part of a series of bisphosphines (n = 1-6) to study the influence of ligand dihedral angles on the enantioselectivity of Ru-catalysed asymmetric hydrogenation of p-ketoesters . 

Nowadays we look with other eyes at organometallic compounds the family of which has expanded enormously. Some members of this family are soluble in water due to their ionic nature the legions of anionic carbonylmetallates (e.g. [Ni(CN)(CO)3] ) and cationic bisphosphine Rh-chelate complexes (e.g. [Rh(BDPP)(COD)] ) just come to mind. Others obtain their solubility in water from the well soluble ligands they contain these can be ionic (sulfonate, carboxylate, phosphonate, ammonium, phosphonium etc. derivatives) or neutral, such as the ligands with polyoxyethylene chains or with a modified urotropin structure. 

The formation of both 12 and 13 during the reduction of 4 in the presence of triphenylphosphine indicated not only that one-half of an equivalent of the added phosphine was taken up, but also that the intermediate formed is the bisphosphine complex, (< 3P) JRhCl, proposed as the reactive intermediate in hydrogenation runs using 1 as the catalyst (1). This assumption is further supported by the fact that the product stereochemistry (cis/trans = 2.0) and lack of double bond isomerization observed on hydrogenation of 7 with this reaction mixture corresponds directly with the data obtained on hydrogenation of 7 using pre-hydro-genated 1 (3). When the reduction of 4 was repeated in the presence of tri-p-tolyphosphine, the carbonyl complex formed was isolated and shown by PMR spectroscopy to contain 1.5 equivalents of triphenylphosphine and 0.5 equivalent of the tri-p-tolyphosphine, as expected. 

A number of chiral bisphosphines related to DiPAMP(l) were prepared and evaluated in asymmetric catalysis. Many variants were closely equivalent but none were superior to the parent compound. In addition, some monophosphines containing sulfone substituents were quite effective. These had the particular advantage of being usable in water solution. Several new DIOP derivatives were tried in the hydroformylation of vinyl acetate but only modest enantiomeric excesses were achieved. A 72% enantiomeric excess was achieved on dehydrovaline under relatively forcing conditions using DiCAMP(3). This result was remarkable since these phosphine ligands generally work very poorly, if at all, on tetrasubstituted olefins. 

The highly efficient stereoselective transformations catalyzed by transition metals that contain BINAP have resulted in extensive efforts in the development of both new Ru-BINAP catalysts and chiral atropisomeric bisphosphines based on biaryl backbones and biheteroaryl backbones.49 Coupled with the various classes of Ru(BINAP) catalysts and chiral bisphosphines, the number of efficient industrial asymmetric hydrogenations are sure to increase because optimization for fine precision and easy optimization in catalyst activity and enantioselectivity made easier.57 66... 

Most catalysts that have been developed for asymmetric catalysis contain chiral C2-symmetric bisphosphines.7 The development of chiral ferrocenylphosphines ventures away from this conventional wisdom. Chirality in this class of ligands can result from planar chirality due to 1,2-unsymmetrically ferrocene structure as well as from various chiral substituents. Two classes of ferrocenylbisphosphines exist two phosphino groups substituted at the l,l -position about the ferrocene backbone (51) and both phosphino groups contained within a single cyclopentadienyl (Cp) ring of ferrocene (4).9... 

A class of chiral bisphosphines based on 3,4-bis(diphenylphosphino)pyrrolidines (9) has been developed by Degussa and the University of Munich. Rhodium-bisphosphine catalysts of this class can reduce a variety of enamides to chiral amino acid precursors with high enantioselectivities. These catalysts are extremely rapid and can operate with high S/C ratios (10,000-50,000) under moderately high hydrogen pressure (150-750 psig). Contrary to other rhodium catalysts that contain... 

A ruthenium catalyst that contained a mixed bisphosphine analogue of Biphemp (106b) was used in the asymmetric hydrogenation of 100. The asymmetric hydrogenation of the bisaryl ketone proceeded with 92% ee at bench scale by Roche.23... 

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