PEG-PS

A final example is the synthesis of H-shaped copolymer of (PS PEG (PS)2 by ATRP, i.e. [209]. The synthetic strategy involves the synthesis of 2,2-bis(methylene a-bromopropionate) propionyl chloride (1), the preparation of 2,2-bis(methylene a-bromopropionate) propionyl-terminated poly(ethylene glycol) (BMBP-PEG-BMBP) (2), and then ATRP of styrene at 110 °C with BMBP-PEG-BMBP/CuBr/2,2/-bipyridine as the initiating system. The structure (3) was configured by using NMR and SEC measurements (Scheme 116). 

Combs and coworkers have presented a study on the solid-phase synthesis of oxa-zolidinone antimicrobials by microwave-mediated Suzuki coupling [38], A valuable oxazolidinone scaffold was coupled to Bal resin (PS-PEG resin with a 4-formyl-3,5-dimethoxyphenoxy linker) to afford the corresponding resin-bound secondary amine (Scheme 7.18). After subsequent acylation, the resulting intermediate was transformed to the corresponding biaryl compound by microwave-assisted Suzuki coupling. Cleavage with trifluoroacetic acid/dichloromethane yielded the desired target structures. 

Amphiphilic resin supported ruthenium(II) complexes similar to those displayed in structure 1 were employed as recyclable catalysts for dimethylformamide production from supercritical C02 itself [96]. Tertiary phosphines were attached to crosslinked polystyrene-poly(ethyleneglycol) graft copolymers (PS-PEG resin) with amino groups to form an immobilized chelating phosphine. In this case recycling was not particularly effective as catalytic activity declined with each subsequent cycle, probably due to oxidation of the phosphines and metal leaching. 

BAL chemistry is compatible with a wide range of functionalized polymeric supports, including PS, PEG-PS, and Synphase crowns. 

PS-PEG-PAMAM[G3.0] dendronized support with HMPB-linker... 

Figure 7.4. Single-bead IR spectra of the product for the reaction 3 at various times on PS = polystyrene, AP = ArgoPore, Tube = Microtube reactor, and PS-PEG = polystyrene-polyethyleneglycol resin.

To assess the versatility of this reaction on solid support, several heterocyclic carboxylic acids were coupled to the PS-PEG resin (PAL linker). Applying the... 

Bradley described the first solid-phase synthesis of PAMAM dendrimers in 1997 [220]. To this end, phthaloyl-protected norspermidine was coupled to aminomethyl functionalised polystyrene-polyethylene-glycol resin ((PS-PEG)-NH2) through an acid-labile linker (see Fig. 23). PAMAM dendrons were assembled by treating deprotected scaffold-bound resin 24 first with an excess of methyl acrylate... 

An amphiphilic polystyrene-poly(ethylene glycol) (PS-PEG) resin-support has been used successfully as a suitable support for asymmetric catalysts in aqueous media. A polymeric (R]-2-(diphenylphosphino) binaphthyl (MOP) ligand 205 anchored onto the PS-PEG resin was shown to be an effective chiral ligand for the enantioselective p-allyhc substitution under aqueous condihons (Scheme 3.67) [130]. 

Heterogeneous aquacatalytic palladium-catalyzed allylic substitution with nitromethane as the Cl nucleophile has been developed by Uozumi (Scheme 3.71). By using an amphiphilic PS-PEG polymer-supported chiral palladium complex, the asymmetric allyhc nitromethylation of cycloalkenyl esters proceeded smoothly in water. For example, when polymer-supported palladium complex 214 was employed in the asymmetric nitromethylation of cycloheptenyl carbonate 215... 

Figure 6.1 Amphiphilic PS-PEG resin-supported palladium-phosphine complexes.

Figure 6.3 A library of PS-PEG resin-supported chiral phosphine ligands.

Thus, the reaction of the cycloheptenyl carbonate 29 with 5 equivalents of dibenzylamine in the presence of 8mol% palladium of the PS-PEG resin-supported 23-Pd complex was carried out in THF or dichloromethane and showed no catalytic activity at 25 °C, whereas the same system in water proceeded smoothly to give 91% yield of the cycloheptenylamine 41a (Scheme 6.4). 

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