Polymer-based reagents

An advantage of polymer-based reagents is that both the excess and the spent reagent are easily separated from the product. Bruno Linclau of the University of Southampton has reported J. Org. Client. 2004, 69,5897) the preparation of a polymer-bound carbodiimide. Exposure of the polymer to alcohol gives a family of O-alkylisoureas that smoothly convert carboxylic acids to the corresponding esters. Methyl, benzyl, ally and p-nitrobenzyl transfer smoothly. The polymeric (-butyl reagent could not be prepared. 

The secondary antibody, which is produced against immunoglobulin of the species from which the primary antibody is derived, is readily prepared with a high order of specificity and affinity. Many commercial sources are available for labeled secondary reagents, including polymer-based reagents. 

We observed that if an amine is used as the cation at C-6, it has significant influence on the quantum yield of singlet oxygen formation from the polymer-based reagent. The observed efficiency of singlet oxygen formation from -rose bengals in which different ammonium ions are substituted at C-6 is shown in Table V. 

The formation of undesirable stable emulsions in phase transfer catalyzed reactions can be avoided by the use of a polymer-based quaternary ammonium chloride as catalyst that can be removed by simple filtration. E. s. S. L. Regen, Am Soc, 97, 5956 (1975) review of polymer-based reagents s. A. Patchornik and M. A. Kraus, Pure Appl. Chem. 43, 503 (1975) polymer-based phase transfer catalysts s. a. M. Cinouini et al., Chem. Commun. 1976, 394... 

Reagents, polymer-based s. Polymer-based reagents -, solid-supported... 

The porosity of the poly(vinylpyridine) resin used is an important factor in determining the efficiency of oxidation of alcohols by poly(vinylpyridinium) chlorochromate and poly(vinylpyridinium) dichromate. Increased porosity also aids in recycling of the polymer-based reagents, which are easily handled in molar amounts. 

Trimethylsilyl ethers are quite susceptible to acid hydrolysis, but acid stability is quite dependent on the local steric environment. For example, the 17o -TMS ether of a steroid is quite difficult to hydrolyze. TMS ethers are readily cleaved with the numerous HF-based reagents. A polymer-bound ammonium fluoride is advantageous for isolation of small polar molecules. ... 

The synthesis of both enantiomers of vasicinone has been carried out using almost entirely polymer-supported reagents. The route was based on functionalisation of deoxyvasicinone by a highly selective bromination then via enantioselective reduction of the derived ketone <06SL2609>. 

Unlike the PEG molecules formed from anionic polymerization techniques, there now exist highly discrete forms of the polymer made by controlled addition of small PEG units to create chains of exacting molecular size. These discrete PEGs have a single molecular weight and do not display the polydispersity of the traditional PEG polymers. See Chapter 18 for a complete discussion of discrete PEG-based reagents and their applications. 

Ley S V, Baxendale IR, Myers RM (2006) The use of polymer supported reagents and scavengers in the synthesis of natural products. In Boldi AM (ed) Combinatorial synthesis of natural product-based libraries. CRC Press Boca-Raton, pp 131-163... 

The advantages of polymer-supported reagents have been exploited for EGBs in the form of EGBs generated from polyacrylamides [74]. The effective base is in all cases an amide anion similar to (33) . 

Functionalisation with bulky hydrophobic carboxylic acids/DCC was studied for the synthesis of amphiphilic polymers based on dextran. Bile acid is covalently bound to dextran (Fig. 27) through ester linkage in the presence of DCC/DMAP (added in dichloromethane) as coupling reagent. 

---