Monosulfonate ligands

BDPP (25-28), the highest rate and enantioselectivity were obtained with the monosulfonated ligand (25) [93, 130, 131] the effect is very pronounced. It should be noted that the Rh/25 catalyst is insoluble in water and during catalysis it moves to the organic phase, where it is supposed to have the structure shown in Eq. (36). 

Later, DeVries, Bakos, and their coworkers confirmed that the enantioselective catalyst for imine reduction is actually monosidfonated ligand 4a prepared via RP-HPLC separation of mixtures of ligands 4a-c. By using monosulfonated ligand 4a as an inseparable mixture of diastereomers (chirahty on phosphorus) under otherwise the same condition,... 

FIGURE 10. Lateral breadths of a series of monosulfonate ligands employed to gauge the resilience of the layered motif in silver sulfonates. 

Hydrogenation reactions in water have been extensively studied and many of the water-solubilizing ligands described in Chapter 5 have been tested in aqueous-organic biphasic hydrogenation reactions. One of the earliest catalysts used was the water-soluble analogue of Wilkinson s catalyst, RhCl(tppms)3 (tppms = monosulfonated triphenylphosphine), but many other catalysts have since been used including [Rh(cod)(tppts)2]+, [Rh(cod)2]+ and [Rh(acac)(CO)2]+ (cod = cyclooctadiene). 

A ligand with great potential for hydroformylation of higher, terminal alkenes is monosulfonated triphenylphosphine, tppms, that was studied by Abatjoglou, also at Union Carbide [12] (section 8.2.6). In this system hydroformylation is carried out in one phase that is worked up afterwards by adding water, which gives two phases to separate catalyst and product. 

As a polar solvent for the catalyst ethylene carbonate (EC), propylene carbonate (PC) and acetonitrile were used. Tricyclohexylphosphine, triphenyl-phosphine and the monosulfonated triphenylphosphine (TPPMS) were investigated as ligands with Pd(acac)2 as the precursor. Cyclohexane, dodecane, p-xylene and alcohols (1-octanol, 2-octanol and 1-dodecanol) were tested as non-polar solvents for the product. To determine the distribution of the product and of the catalyst, the palladium precursor and the hgand were dissolved in the polar solvent and twice as much of the non-polar solvent was added. After the addition of 5-lactone, the amounts of the product in both phases was determined by gas chromatography. The product is not soluble in cyclohexane and dodecane, more than 99% of it can be found in the polar catalyst phase. With the alcohols 1-octanol, 2-octanol and dodecanol about 50 to 60% of the 5-lactone are located in the non-polar phase. With p-xylene biphasic systems can only be achieved when EC is used as the polar solvent and even in this solvent system one homogeneous phase is formed at a temperature higher than 70 °C. In a 1 1 mixture of EC and p-xylene about 50 to 60% of the product is contained in the polar phase. 

The rhodium catalyst currently used for this step utilizes a monosulfonated phosphine ligand, dissolved N-methyl-2-pyrrolidinone (NMP).(6) This catalyst system has shown adequate activity and stability. More importantly, it enables product-catalyst phase separation. (7)... 

It occurred to us that ionic interactions might be a highly suitable binding motif to enforce the formation of heterobidentate ligand combinations [48[. The assembly ligand 14 /IS has been formed from the well-known TPPMS (14, monosulfonated triphenylphosphine sodium salt) and 3-(diphcnylphosphinyl)aniline hydrochloride (IS) by a simple ion-exchange reaction (Scheme 10.6). The coordination behavior ofthe ion-pair 14 /I S has been tested with various transition metal complexes. Other... 

Another approach to increase solution stability and decrease the number of isomers in [99mTc]HYNIC complexes involves the use of a water-soluble phosphine (Fig. 2 TPPTS, disodium triphenylphosphine-3,3 -disulfonate, TPPDS, and sodium triphenylphosphine-3-monosulfonate, TPPMS) as a second coligand [42]. It was found that the combination of XV120 with tricine and a phosphine coligand results in a versatile ternary ligand system that forms 99mTc... 

The use of triphenylphosphine as ligand led to acceptable rates in ILs, but with high rhodium leaching into the organic phase. Recourse to sulfonated phosphines such as monosulfonated triphenylphosphine retained the catalyst in the ionic liquid phase but decreased its activity significantly. This drawback was surmounted by the use of 47 (Table 1.5), which was derived from a simple cation metathesis reaction between TPPTS (37) and 1-butyl-2,3-dimethylimi-dazolium chloride [bdmim][Cl] in acetonitrile. 

In 2009, Xiao employed a half sandwich Cp lr(l 11) complex with different chiral monosulfonated OPEN ligands (Figure 7.2), earlier developed for imine reduction by the same group, in combination with a BINOL based chiral phosphate counteranion (TRIP anion), to reductively aminate 24 acetophenone derivatives (1.2 equiv) with p anisidine (limiting reagent) under the conditions of 1.0 mol% of the indicated Ir catalyst (Table 7.1), 5 bar (73 psi) H2, toluene, 35 °C, and 15 24h [14]. 

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