Phosphines polymer-bound

Plenio et al. tested an adamantyl phosphine ligand bound to soluble polystyrene (Figure 4.43) in various palladium-catalyzed C-C coupling reactions.[62] The retention of metal complexes of the polymer-bound phosphine ligand were determined to be higher than 99.95%. 

A number of modified reaction conditions have been developed. One involves addition of silver salts, which activate the halide toward displacement.94 Use of sodium bicarbonate or sodium carbonate in the presence of a phase-transfer catalyst permits especially mild conditions to be used for many systems.95 Tetraalkylammonium salts often accelerate reaction.96 Solid-phase catalysts in which the palladium is complexed by polymer-bound phosphine groups have also been developed.97 Aryl chlorides are not very reactive under normal Heck reaction conditions, but reaction can be achieved by inclusion of triphenylphosphonium salts with Pd(OAc)2 or PdCl2 as the catalyst.98... 

FIGURE 10. Reaction between polymer-bounded phosphines and methyl iodide relative extinction of 1123cm-1 phosphonium bond in comparison with the iodine concentration in copolymers (styrene-divinylbenzene)104... 

Phosphonium perbromides, particularly polymer-bound phosphines, have also been proposed as bromine carriers and reagents5. 

The homogeneous chiral phosphine/DPEN-Ru catalyst can be immobilized by use of polymer-bound phosphines such as polystyrene-anchored BINAP (APB-BINAP) [57, 98], Poly-Nap [99], and poly(BINOL-BINAP) [100], poly(BINAP) [101]. These complexes hydrogenate T-acetonaphthone and acetophenone with S/C of 1000-10 000 under 8 10 atm H2 to give the corresponding secondary alcohols in 84-98% e.e. The recovered complexes are repeatedly used without significant loss of reactivity and enantioselectivity. Immobilization allows the easy separation of catalyst from reaction mixture, recovery, and reuse. These advantages attract much attention in combinatorial synthesis. 

The reaction of an alcohol and a carboxylate anion with diethyl azodicarbox-ylate EtOOCN=NCOOEt and PhsP is called the Mitsunobu esterification reac-tion. This reaction can also be considered as an 8 2. Other Mitsunobu catalysts are available, " and a polymer-bound phosphine has been used. A renewable phosphine ligand has been developed. Note that other functional groups, including azides and thiocyanates can be generated from alcohols using Mitsunobu conditions. 

Miscellaneous Methods of Preparing Phosphines. A review of methods for the preparation of polymer-bound phosphines (and their applications) has... 

DEAD,PhMe,PhCOOH polymer-bound phosphine... 

This chapter is a comprehensive review of alkene syntheses with polymer-supported Wittig reagents to produce soluble and polymer-bound alkenes. It does not include polymerizations of difunctional phosphoranes with difunctional carbonyl compounds, polymer-bound ylides of elements other than phosphorus, or other synthetic and catalytic uses of polymer-bound phosphines. 

The polymer-bound phosphinate 10 has been prepared by successive treatments of 2% cross-linked brominated polystyrene with n-butyllithium, diethylchlorophosphite, and ethyl bromoacetate. It was used to form alkenes from aldehydes and ketones, but the yields were not consistently high, and the reagent was contaminated with an unidentified polymer-bound phosphorus species (52). 

In summary, polymer supports have succeeded in breaking dimeric metal complexes into monomeric species in several cases where the polymeric amine or phosphine ligand is present in large excess. Organometallic complexes at high concentrations in solvent-swollen polymers still tend to exist in dimeric form. However, many of the spectral studies have failed to mention that polymer-bound phosphines can be oxidized to phosphine oxides, a facile reaction with adventitious air in a solvent-swollen phosphine polymer (78). Many of the samples may have contained phosphine oxide as well as phosphine. 

Synthesis of polymers 41 Poly(styrene-co-divinylbenzene) (2 wt. %) was used as the starting polymer. 17 g of this copolymer is placed in a round-bottomed flask together with 128 mL of PCI3 and allowed to swell for 30 min. Fresh, powdered aluminum chloride is added (20.2 g) and the entire mixture is shaken at 20 °C for 24 h. After that time the beads are filtered off, washed briefly with dioxane and dropped into a 1-L beaker containing ice and sodium chloride solution. After washing with distilled water, the beads are left overnight in ca. 3 M NaOH solution followed by standard conditioning. A polymer-bound phosphinic acid is obtained by this procedure. 

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