Monophosphines sulfonated

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. 

As already outlined in Section 3.2.1, several water-soluble monophosphines, such as TPPTS, have been synthesized by controlled sulfonation in oleum. In the same way several diphosphines have been sulfonated (Structures 1-5). Although the number of chiral diphosphines reported is ever increasing, the number of sulfonated achiral diphosphines remains limited and includes BINAS-8 (1) [3, 4] and BISBIS (2) [5], both of which contain an aromatic bridge between the two phosphi-... 

Several representatives of the widely studied tertiary phosphine ligands for enantioselective hydrogenation in aqueous solutions are shown as Structures 21 -39. It is seen that the most successful ligands in this field do have their water-soluble, mostly sulfonated, derivatives [7, 11]. In case of acid-sensitive compounds, solubility in water could be achieved by attaching dimethylamino substituents to the parent arylphosphines and by their further protonation or quaternization. Monophosphines, such as 21 [88], played a minor role in comparison with the chelating diphosphines. Water-soluble phosphine-phosphinite ligands (L) were obtained from trehalose and used as components of with [Rh(cod)(L)[BF4]] catalysts for the enantioselective hydrogenation ofenamides [157]. 

X-Phos is probably the most active and versatile ligand of the biphenyl monophosphines for C—N bond formations [30], It is one of the very few ligands that was found applicable to the conversion of nonfluorinated sulfonic esters [30]. These substrates are very attractive from an economical point of view [30]. 

Also, 1-dodecene can be selectively reacted with syngas in the presence of a Rh(BIPHEPHOS) catalyst to give n-tridecanal (Table 6.1, entry 5). A related Rh catalyst based on nanoparticles (2.7-4.8 nm) could be three times recycled without loss of activity when the reaction was conducted in a thermomorphic solvent system [61]. Also, under the conditions illustrated in Scheme 6.6 ( = 4), tridecanal is formed, but in comparison to shorter chain olefins the conversion dropped and the aldehyde was obtained only in a moderate Ub ratio [54]. Other attempts have been based on more sophistic ligands such as amphiphilic sulfonated monophosphines [62] and diphosphines [55, 63], phosphine-functionalized phosphonium ionic liquids [64], and MeO-substituted phosphines [65]. Tridecanal has a slightly floral scent reminiscent of citrus and grapefruit peel. 

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