Post-functionalization

A well-spread example is the acetylation, which is commonly used as a protective reaction but can also be applied as a post-functionalization in order to separate isomers47 (Scheme 40). In some cases, however, the separation of A-acetyl OZTs can be tedious, due to their relative instability. 

Erb W, Neuville L, Zhu JP (2009) Ugi-post functionalization, from a single set of Ugi-adducts to two distinct heterocycles by microwave-assisted palladium-catalyzed cyclizations tuning the reaction pathways by ligand switch. J Org Chem 74 3109-3115... 

Polyelectrolytes may be synthesized by a variety of post-functionalization techniques in which ionogenic groups are introduced into the structure of an existing nonionic polymer. For an excellent review of polymer functionalization reactions the reader is referred to the recent book by Akelah and Moet [65]. In this paper, representative examples of the major polymer modification techniques for polyelectrolyte synthesis will be presented. 

As electrophiles for post-functionalization of awfi-carbomagnesiation, aryl and alkenyl halides can also be used when Pd catalyst is employed. By merging such Pd-catalyzed arylation, tamoxifen can be synthesized in a stereoselective manner (Scheme 36) . ... 

Fleming and coworkers have developed a number of such multicomponent assembling reactions using alkyl halides, aldehydes, ketones and acid chlorides as electrophiles for post-functionalization of carbomagnesiation . The stereoselectivity of the reaction with electrophiles is not only generally high but also highly dependent on the nature of electrophiles. 

In addition to post-functionalizing polymers by bonding the macrocycle to the preformed polymer backbone, macrocycles can be incorporated into polymer matrices by direct polymerization of the macrocycle, either by a step-growth mechanism or a chain-growth mechanism. [46] Polymeric crown ether stationary phases were pioneered by Blasius et al. [34, 59-62] These resins were used to separate both cations (including protonated amines) with a common anion, and anions with a common cation in high... 

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For the post-functionalized materials, the silanols present within the channels provide a suitable anchoring site for chemical attachment. Although the wall composition contains random interatomic bond angles and atomic location, there exists an uncharacteristically large and uniform density of silanol groups (other than the silanols that exist due to incomplete condensation) within the channels due to surfactant packing requirements. NMR studies showed that up to 40% of the silicon atoms located on the surface of the walls could be associated with hydroxyls [62],... 

Post-functionalization reactions were employed for the synthesis of macromonomers. For example Tsukahara et al. used carboxyl-terminated PS and glycidyl methacrylate [90] for this purpose (Scheme 35). 

IR spectroscopy is well suited to monitor the progress of post-functionalization reactions—for example, for the quaternization of P4VP (see Figure 4.IB) or the hydrolysis or reduction of poly(vinylfor-mamide) to yield primary amines (see Figure 4.1C) [1,2]. Moreover, the presence of undesired by-products such as boric acid after using borane/THF adducts for the aforementioned reduction reaction can be detected. 

The methods used for synthesis of ionic polymers can be divided mainly into three types (1) direct synthesis, (2) post-functionalization of a standard preformed polymer, and (3) post-functionalization of a special preformed polymer. 

All of the aforementioned ionomers are anionic polymers. Cationic polymers are less common, though equally important. Pendant cations are usually of the quaternary ammonium type and made by a multi-step post-functionalization in which a precursor containing labile chloride is reacted with a tertiary amine ... 

Polymers with a polytetrafluoroethylene (PTFE) backbone and pendant perfluorosulfonate or perfluor-ocarboxylate groups have become commercially important materials, although they are expensive. The sulfonates were introduced as Nafion by Du Pont in the early 1970s and the carboxylates as Flemion by Asahi Glass in 1978. They are made by free-radical copolymerization of tetrafluoroethylene and perfluorovinyl monomers giving precursor copolymers, (XXII) and (XXIII), which can be post-functionalized by hydrolysis to generate sulfonic and carboxylic acid groups. The perfluorovinyl... 

Commercial polysulfones (see Table 4.30) such as Udel (Union Carbide) and Victrex (ICI) are sulfonated in a post-functionalization step to make ionomers. When dissolved in dichloroethane and treated with a complex of sulfur trioxide and triethyl phosphate, Udel (XXIV) becomes monosulfonated on the rings marked R (as the rings connected to the sulfone group are deactivated by the sulfone group). 

For CRP based on a reversible termination process, the strategy was to synthesize water-soluble macroinitiators (with either an alkoxyamine or an alkyl halide chain-end) by direct CRP or by post-functionalization, before using them as both initiators and stabilizers in emulsion polymerization of a hydrophobic monomer. 

David et al have tested these new diblock copolymers as additives for adhesion/anticorrosive properties of metals. In order to protect against corrosion, a coating system was prepared consisting of a blend of poly(VDF) (inhibiting water penetration) with poly(MMA)-Z)-poly(monophosphonic acrylate) diblock copolymer with 10 wt% [compared to poly(VDF)]. This diblock copolymer was obtained by atom transfer radical polymerization using post-functionalization and hydrolysis to introduce the phosphonic acid function onto the polymeric backbone. The anticorrosive properties of virgin poly(VDF) were also determined without any additive to be compared... 

Y. Li, K. Kamata, S. Asaoka, T. Yamagishi and T. lyoda. Efficient anodic pyridination of poly(3-hexylthiophene) toward post-functionalization of conjugated polymers. Org. Biomol. Chem. (1), 1779-1784 (2003). 

Another approach to tuning the optical properties and improving the emission of PT derivatives in the solid state was proposed by Holdcroft and co-workers [60], They used post-functionalization of P3HT (9f) by an electrophilic substitution reaction (to afford polymers 34) followed by Pd-catalyzed coupling (Suzuki, Stille or Heck reactions) to afford polymers 35 (Scheme 19.5) [61], In this case, functionalization with bulky aryl substituents (35) hindered the interchain interactions and allowed a substantial increase in d>PL in the films from 1.6 % to 13-22 %. 

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