Polymers reagents

Soluble polymer supports, like their insoluble counterparts, offer the advantage of ease of separation. After carrying out a chemical process, the polymer reagent, catalyst, or substrate can be isolated by adding a nonsolvent, for instance, by adding isopropanol for PEG supports. 

A wide range of polymer reagents have been studied [Akelah and Sherrington, 1983 Blossey and Ford, 1989 Ford, 1986a Kirschning et al., 2001], The epoxidation of an alkene by a polymer peracid illustrates the use of a polymer reagent [Frechet and Haque, 1975]. Chloro-methylated polystyrene is treated with potassium bicarbonate in dimethylsulfoxide to yield 

Mixture of spent polymer reagent + desired product 

Oxidation of alcohols to aldehydes or ketones is accomplished with chromate bound to an anion-exhange resin (XXXIX with A = HC1O4 ) [Frechet et al., 1981 Taylor, 1986]. Other oxidants include polymers functionalized with CIO-, CICr04, and RuOj [Kirschning et al., 

The use of a chiral polymer instead of the achiral polymers in XXXIX and XXXX allows an asymmetric synthesis. An example is the stereoselective reduction of acetophenone to (I )-l-phenylethanol in 76-97% enantiomeric excess by using the indicated chiral support (Eq. 9-69) [Itsuno et al., 1985]  

The reactions of reactive resins can be considered as special cases of polymer analog reactions. Reactive resins can be subclassified as polymer reagents and ion-exchange resins. Also, special cases occur when two reactive groups on the same chain react with bifunctional reagents (cycliza-tion and transannulation). 

Polymer reagents of this type may be ion-exchange resins (see Section 23.3.3) or electron transfer polymers (oxidation/reduction polymers). Polymer reagents are also used in the Merrifield synthesis of peptides and proteins (see Section 30.3.2). Other polymer reagents, together with their applications, are  

Because of the neighboring group effect, the reactions of high- and low-molecular weight compounds do not always proceed in the same way  

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Other reasons for a wide propagation of polymerization in water include (1) reduction of energy consumed to separate the initial monomer in crystal form (acrylamide is produced and used in the aqueous solution form), which, in addition, is associated with the probability of its spontaneous polymerization, and (2) recovery of the organic solvents, which results in less environmental pollution and the elimination of the stage of solution of polymer reagents used, as a rule, in the form of the aqueous solutions. 

Polymer Reagent Reactant Ratio Tempt C) Time(h) % Subst (DF) [ql (Iq]) Reagent Polymer SnCl4... 

Hager, H.J. (1974) Latex polymer reagents for diagnostic tests. US Patent 3,857,931. 

Fig. 2. Diagram illustrating the immune polymer method, Dako s Envision . This is a two step, fast method which allows the use of more dilute primary antibody. The enzyme-containing polymer reagent is "universal" in that it contains antirabbit/mouse immunoglobulins and will bind to rabbit or mouse primary antibodies (A, immunoglobulin , peroxidase enzyme).

The functionalization of polymer approach is used much more often than the functionalization of monomer approach at present because functional polymers such as chloro-methylated polystyrene are readily available with different porosities and degrees of chloromethylation. There are relatively few situations where less work is needed to use the functionalization of monomer approach. Also, many practitioners of polymer reagents,... 

Fig. 9-1 Scheme for utilization of a polymer reagent. The epoxidation of an alkene by a polymer... 

Other polymer reagents have been studied for performing nucleophilic substitution, alkylation, acylation, deprotonation, and other reactions [Kirschning et al., 2001]. 

Polymers containing chiral groups are useful for resolving racemic mixtures into the individual enantiomers [Kiniwa et al., 1987 Mathur et al., 1980 Wulff et al., 1980]. For example, the copper(II) complex of XXXXIII (either the R- or S-enantiomer) resolves racemates of amino acids [Sugden et al., 1980], The separation is based on the formation of a pair of diastereomeric complexes from the reaction of the polymer reagent with the two enantiomers. One of the enantiomers is complexed more strongly than the other and this achieves separation of the enantiomers. 

Show by equations how to synthesize each of the following polymer reagents ... 

For the 9-fluorenylmethoxycarbonyl (Fmoc) protection of amino acids, Chinchilla et al.36,37 prepared a similar ROMP-polymer that supports an activated. V-hydroxysuccinimide Fmoc-carbonate (Table VII, entry 31). Various Fmoc-amino acids are prepared in pure form after removal of the polymer reagent by filtration and aqueous phase separation. 

Advanced Polymer Reagents Based on Activated Reactants and Reactive Intermediates Powerful Novel Tools in Diversity-Oriented Synthesis... 

One of the major innovations in combinatorial and medicinal chemistry in recent years aiming at efficient diversity-oriented synthesis has been the implementation of polymer reagents in polymer-assisted solution phase (PASP) synthesis. This contribution will present—following an introduction to the field—a concept of advanced polymer reagents based on reactive intermediates and active reactants that should extend the scope PASP synthesis significantly. Experimental procedures describing preparation and use of the novel polymer reagents are included. 

Fig. 1. Polymer-assisted solution phase (PASP) synthesis combines the merits of solution-phase chemistry with the advantages of facilitated phase separation by using polymer reagents (a) or scavenger resins (b).

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