Phosphine-modified polymer

The hnker is stable to a great variety of reaction conditions. In the example illustrated in Scheme 46, the alkynes are loaded indirectly onto the phosphine-modified polymer as their hexacarbonyldicobalt(O) complexes, but they can also be attached to a Co-coated polymer. Instead of traceless release of the alkynes after modification, they can also be apphed to Pauson-Khand reactions to form cyclo-pentenones [119]. 

Polymers can be modified by methods similar to those described above for metal oxides. For example, chloromethylated polystyrene reacts with diphenylphosphide to yield a phosphinated polystyrene (eqnation 4). The modified polymer can then be nsed as a hgand for a variety of... 

Cyclopentadienyl groups can be incorporated in a manner similar to that shown in eqnation(4) for phosphines. Metallocene derivatives (see Metallocene Complexes),mtani, can be incorporated into these modified polymers. Also, chiral phosphines such as DIOP and BINAP have been immobilized on polymers to be used in asyimnetric hydrogenation catalysis and related reactions. ... 

The use of catalysts based on polymers with inverse temperature solubility, often copolymers of TV-isopropy-lacrylamide, to allow recovery by raising the temperature to precipitate the polymer for filtration,9 was mentioned in Chap. 5. The opposite, if the catalyst is soluble hot, but not cold, has also been used in ruthenium-catalyzed additions to the triple bonds of acetylenes (7.1).10 The long aliphatic tail of the phosphine ligand caused the catalyst to be insoluble at room temperature so that it could be recovered by filtration. There was no loss in yield or selectivity after seven cycles of use. A phosphine-modified poly(A-iso-propylacrylamide) in 90% aqueous ethanol/heptane has been used in the hydrogenation of 1-olefins.11 The mixture is biphasic at 22°C, but one phase at 70°C, at which the reaction takes place. This is still not ideal, because it takes energy to heat and cool, and it still uses flammable solvents. 

This reaction has been modified for various conditions, such as the application of microwave irradiation and the application of phosphine-containing polymer prepared from the ruthenium-catalyzed ring-opening metathesis polymerization of the norbornene. Most importantly, this reaction has been extended to the coupling of primary or secondary alkyl halides with aryl, vinyl, and even alkyl halide (or tosylate) 31,3o,3p,3y,3dd,3nn,4v,4x,6... 

Acrylonitrile can be replaced by acrylic esters in these processes (S6). It is difficult to explain why these reactions afford only linear condensation products and not aromatic oi cycloolefinic compounds. Bis(acrylonitrile)-nickel also reacts with 2-butyne (78) and hexafluorobutyne (88), forming the corresponding benzene derivative and linear oligomers and polymers, respectively. Since phosphine-modified nickel carbonyls usually fail to... 

In conclusion, we have presented a new method for the preparation of tertiary phosphine oxides of the type R2R P0 from a secondary phosphine oxide and an alkyl halide with excellent yields, using phase transfer catalysis. Furthermore, this method can be successfully applied to the chemical modification of soluble and cross-linked polystyrenes. Examination of the molecular weights, M, and of the composition of the modified polymers indicates that no side reactions or degradation occur in the conditions we have used. Further work in this field is in progress. 

As summarized in Sect. 3, the synthesis of grafted polymers requires side chain functionalities on the main chain as well as chain end functionalities on the polymers forming the arms. Besides, chain end modified polymers themselves exhibit highly interesting properties. To obtain chain end modificatimis, weU-defined chain ends are a primary requirement and can be obtained via controlled polymerizatiOTi techniques and subsequent chain end modification. For example, Sumerlin and coworkers reduced the thioester of poly(iV-isopropylacrylamide) (PNIPAM prepared by RAFT polymerization) using 1-hexylamine in the presence of tributyl-phosphine to yield a thiol-terminated polymer (Scheme 13). Subsequently, a bismaleimide was used to coimect the PNIPAM and other thiols. Thereby, small organic molecules could be used as well as other polymers or thiol-containing proteins [20, 21]. 

Numerous diamines and aromatic dianhydrides have been investigated. WhoUy aromatic Pis have been stmctiirally modified by incorporating various functional groups, such as ether, carbonyl, sulfide, sulfone, methylene, isopropjlidene, perfluoroisopropyUdene, bipyridyls, sdoxane, methyl phosphine oxide, or various combinations of these, into the polymer backbone to achieve improved properties. The chemistry and apphcations of Pis have been described in several review articles (4). 

These appHcations are mosdy examples of homogeneous catalysis. Coordination catalysts that are attached to polymers via phosphine, siloxy, or other side chains have also shown promise. The catalytic specificity is often modified by such immobilization. Metal enzymes are, from this point of view, anchored coordination catalysts immobilized by the protein chains. Even multistep syntheses are possible using alternating catalysts along polymer chains. Other polynuclear coordination species, such as the homopoly and heteropoly ions, also have appHcations in reaction catalysis. 

For the synthesis of carbohydrate-substituted block copolymers, it might be expected that the addition of acid to the polymerization reactions would result in a rate increase. Indeed, the ROMP of saccharide-modified monomers, when conducted in the presence of para-toluene sulfonic acid under emulsion conditions, successfully yielded block copolymers [52]. A key to the success of these reactions was the isolation of the initiated species, which resulted in its separation from the dissociated phosphine. The initiated ruthenium complex was isolated by starting the polymerization in acidic organic solution, from which the reactive species precipitated. The solvent was removed, and the reactive species was washed with additional degassed solvent. The polymerization was completed under emulsion conditions (in water and DTAB), and additional blocks were generated by the sequential addition of the different monomers. This method of polymerization was successful for both the mannose/galactose polymer and for the mannose polymer with the intervening diol sequence (Fig. 16A,B). 

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... 

Phosphorus FR compounds cover a wide range of chemical structures not only as additives incorporated in the molten state in thermoplastics but also as reactive components introduced as monomers in thermoset polymers phosphates, phosphonates, phosphinates, phosphine oxides, phosphites, red phosphorus, etc. They can be also used as layered silicate modifiers. Organic phosphates and red phosphorus are among the most frequent additive FRs used in various non-polyolefinic polymers. 

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