Polystyrene treatment with

As an extension to their work, the same group have prepared polymer-supported Zr di-Ind complex 251 from polystyrene (Scheme 89). Lithiation of the polystyrene, treatment with 1,4-dibromobenzene, and further lithiation gave 249 which was treated with PhSi(Ind)2Cl to give the supported ligand 250. The metal complex 251 was formed by treatment of this with ZrCU. The use of 251 for ethane polymerization was assessed and subsequently the mechanism of polyethylene growth on the surface of the supported catalyst beads has been studied. 

When used as substitutes for asbestos fibers, plant fibers and manmade cellulose fibers show comparable characteristic values in a cement matrix, but at lower costs. As with plastic composites, these values are essentially dependent on the properties of the fiber and the adhesion between fiber and matrix. Distinctly higher values for strength and. stiffness of the composites can be achieved by a chemical modification of the fiber surface (acrylic and polystyrene treatment [74]), usually produced by the Hatschek-process 75-77J. Tests by Coutts et al. [76] and Coutts [77,78] on wood fiber cement (soft-, and hardwood fibers) show that already at a fiber content of 8-10 wt%, a maximum of strengthening is achieved (Fig. 22). 

Strongly basic anion exchangers (polystyrene quaternary ammonium resins). These resins (Duolite A113, Amberlite 400, etc.) are usually supplied in the chloride form. For conversion into the hydroxide form, treatment with 1M sodium hydroxide is employed, the volume used depending upon the extent of conversion desired two bed volumes are satisfactory for most purposes. The rinsing of the resin free from alkali should be done with de-ionised water free from carbon dioxide to avoid converting the resin into the carbonate form about 2 litres of such water will suffice for 100 g of resin. An increase in volume of about 20 per cent occurs in the conversion of the resin from the chloride to the hydroxide form. 

Under nitrogen, 115( 1 eq.) was reacted with BuLi (2 eq.) at 0°C for 1 h followed by treatment with trimethyltin chloride (2.5 eq.) in THF at room temperature for 30 min. Then a solution of 116 (1 eq.) and PdCl2(Ph3As)2 (0.02 eq.) in THF was combined and the mixture was stirred at reflux overnight. The polymer was precipitated with MeOH followed by filtration and dried under vacuum. GPC (polystyrene standards) Mn = 2000. 

CE has been used for the analysis of anionic surfactants [946,947] and can be considered as complementary to HPLC for the analysis of cationic surfactants with advantages of minimal solvent consumption, higher efficiency, easy cleaning and inexpensive replacement of columns and the ability of fast method development by changing the electrolyte composition. Also the separation of polystyrene sulfonates with polymeric additives by CE has been reported [948]. Moreover, CE has also been used for the analysis of polymeric water treatment additives, such as acrylic acid copolymer flocculants, phosphonates, low-MW acids and inorganic anions. The technique provides for analyst time-savings and has lower detection limits and improved quantification for determination of anionic polymers, compared to HPLC. 

Deliberate production of (vinyl)polystyrene from (toluenesul-foxyethyl)polystyrene or (haloethyl)polystyrenes was best accomplished by quaternization with N,N-dimethylaminoethanol, followed by treatment with base beta-deprotonation is encouraged in the cyclic zwitterionic intermediate. Reaction was faster and cleaner than with other reagents recommended (64, 76, 77) for eliminations, such as alkoxide, diazabicycloundecene or quaternary ammonium hydroxide this new and efficient procedure may find application elsewhere. Hydrometallation or other additions to polymer-bound olefin may prove useful steps in future syntheses by polymer modification. 

Hydroxamic acids are an important class of compounds targeted as potential therapeutic agents. A-Fmoc-aminooxy-2-chlorotrityl polystyrene resin 61 allowed the synthesis and subsequent cleavage under mild conditions of both peptidyl and small molecule hydroxamic acids (Fig. 14) [70]. An alternative hydroxylamine linkage 62 was prepared from trityl chloride resin and tV-hydroxyphthalimide followed by treatment with hydrazine at room temperature (Scheme 30) [71]. A series of hydroxamic acids were prepared by the addition of substituted succinic anhydrides to the resin followed by coupling with a variety of amines, and cleavage with HCOOH-THF(l 3). 

In the early 1970 s, Bayer et al. reported the first use of soluble polymers as supports for the homogeneous catalysts. [52] They used non-crosslinked linear polystyrene (Mw ca. 100 000), which was chloromethylated and converted by treatment with potassium diphenylphosphide into soluble polydiphenyl(styrylmethyl)phosphines. Soluble macromolecular metal complexes were prepared by addition of various metal precursors e.g. [Rh(PPh3)Cl] and [RhH(CO)(PPh3)3]. The first complex was used in the hydrogenation reaction of 1-pentene at 22°C and 1 atm. H2. After 24 h (50% conversion in 3 h) the reaction solution was filtered through a polyamide membrane [53] and the catalysts could be retained quantitatively in the membrane filtration cell. [54] The catalyst was recycled 5 times. Using the second complex, a hydroformylation reaction of 1-pentene was carried out. After 72 h the reaction mixture was filtered through a polyamide membrane and recycled twice. 

N-Fmoc-aminooxy-2-chlorotrityl polystyrene (212 mg, 0.95 mmol g 1,0.2 mmol) was placed in a reaction column (1.0 cm diameter alternatively, an appropriate reaction vessel can be used, e.g., Quest 210 synthesizer 5-mL reaction vessel) and preswollen in DCM DMF (1 1, 3mL) for 24 h (note 4). The resin was then washed with DMF (10min, 2.5 mL min-1) and Fmoc-depro-tected by treatment with 20% v/v piperidine in DMF (10 min, 2.5mL min-1). The resin was then washed with DMF (lOmin, 2.5 mL min ), after which excess DMF was removed. 

Acidolytic treatment using DCM hexafluoroisopropanoI (1 1) for 2 h at ambient temperature afforded the hydroxamic acid in only 45% yield. However, it is worth noting that the tethered Fmoc-N(Pr)-<9-2-chIorotrityI polystyrene, on treatment with similar acidolytic cocktail effected quantitative release of Fmoc-N(Pr)-OH. 

V-(9-Fluorcnylmethoxycarbonyl)aminooxy-2-chlorotrityl polystyrene was then N-deprotected within minutes by treatment with 20% v/v piperidine in DMF to afford the key intermediate aminooxy-2-chlorotrityl polystyrene. With this in hand, N-acylation was then carried out and, where appropriate, followed by a series of chemical transformations to yield resin-bound... 

The present procedure2 describes the conversion of resin-bound, primary aliphatic amines into isothiocyanates and the conversion of the latter into 3-aminothiophenes. The generation of isothiocyanates is related to known procedures,3 in which amines are first treated with carbon disulfide and the resulting dithiocarba-mates are desulfurized by treatment with a condensing agent (alkyl chloroformates, carbodiimides, lead or mercury salts, etc.). The presence of resin-bound isothiocyanates on the polystyrene support could be qualitatively ascertained by infrared spectroscopy (KBr-pellet strong absorption at 2091 cm-1). 

As has been described in Section 4.2.3, immobilized TADDOL-derivatives are particularly important catalytic species which can be applied to asymmetric synthesis in many ways. Seebach et al. developed a dendritic elongated TADDOL-deri-vative (32) that could be embedded in polystyrene by copolymerization (Scheme 4.18). Upon treatment with Ti(OiPr)4 the chiral polymeric diisopropoxy-Ti-TAD-... 

The reactions of A -BOC-protected a-amino acids 424 and diazomethane in the presence of iV-methylmorpholine-polystyrene and isobutyl chloroformate resulted in formation of diazoketones 425, which, on treatment with indium(lll) triflate, were cyclized to 4-substituted-tetrahydro-l,3-oxazine-2,5-diones 426 in high overall yields (Scheme 82) <2006TL7969>. 

Treatment of polystyrene particles with dialdehyde caused the introduction of aldehyde groups onto the particles (3). The aldehydes are used as binding sites for functional compounds. Carboxyl groups on particles are also in common use as a... 

Ni(COD)2], supported catalyst activated by treatment with AIEt2(OEt) Phosphinated cross-linked polystyrene Butadiene 3,5... 

To overcome problems associated with the removal of iodobenzene and its derivatives formed upon fluorination of arylalkenes and arylalkynes with (difluoroiodo)arenes, polymer-supported (difluoroiodo)arenes were proposed.139 With these agents, the separation procedures are reduced to filtration of the iodinated polymer. For this purpose popcorn polystyrene is io-dinated and then transformed into the difluoroiodide by treatment with xenon difluoride in the presence of hydrogen fluoride in dichloromelhane at 25 C. The amount of active fluorine bonded to iodine atoms on the polymer support is estimated by iodometric titration. The reactions with phenyl-substituted alkenes result in rearranged gew-difluorides. The procedure provides the same fluorination products as with (difluoroiodo)benzenc (see Section 4.13.) but in much higher yields, e.g. PhCF2CH2Ph (96%), PhCF2CH(Me)Ph (95%). PhCH2CF2H (86%), and l,l-difluoro-2-phenylcyclopentanc (91 %). 

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