Polymer-Assisted Methods

These methods are based on the mixture of metal precursors and soluble polymers in a solution. The high molecular weight of these polymers provides 

Single oxide thin films (e.g., ZnO, Ti02, or EU2O3) and complex perovskite oxides (e.g., SrTiOs, BaTiOs, or YBa2Cu307) have been grown from these solutions [29]. 

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Different strategies in the solution are described in the literature for the preparation of CSD precursors, where the prominence of the type of chemicals transcends the former grouping of solution methods. In general, but especially in the case of complex oxide compositions, neither of them can be used alone to obtain the liquid precursor due to difficulties in finding available metal reagents of the same family (e.g., alkoxides, carboxylates, and p-diketonates) for all the cations involved in the system. Therefore, a combination of several approaches is used to stabilize all the metal reagents in a common and stable solution. Some of these methods are shown here. They are divided considering the type of precursor used to obtain a stable solution, more than the traditional classification of solution methods shown above. Seven major solution processes are explained next alkoxide-based methods, carboxylate- and p-diketone-based methods, Pechini methods, diol routes, amine-based methods, polymer-assisted methods, and aqueous solution-gel methods. 

If small or medium libraries for lead optimization are demanded and all synthetic products are to be screened individually, most often parallel synthesis is the method of choice. Parallel syntheses can be conducted in solution, on solid phase, with polymer-assisted solution phase syntheses or with a combination of several of these methods. Preferably, parallel syntheses are automated, either employing integrated synthesis robots or by automation of single steps such as washing, isolation, or identification. The latter concept often allows a more flexible and less expensive automation of parallel synthesis. 

A method for microwave-assisted transesterifications has been described by Van-den Eynde and Rutot [73], The authors investigated the microwave-mediated deriva-tization of poly(styrene-co-allyl alcohol) as a key step in the polymer-assisted synthesis of heterocycles. Several /i-ketoesters were employed in this procedure and multigram quantities of products were obtained when neat mixtures of the reagents in open vessels were subjected to microwave irradiation utilizing a domestic micro-wave oven (Scheme 7.65). The successful derivatization of the polymer was confirmed by IR, 1H NMR, and 13C NMR spectroscopic analyses. The soluble supports... 

Fig. 7 Scheme of the preparation of LDH/polymer nanocomposites (a) in situ polymerization, (b) direct incorporation of polymer, (c) restacking or reconstruction, and (d) guest displacement or solvent-assisted method... 

POLYMER-ASSISTED SOLUTION-PHASE METHODS FOR CHEMICAL LIBRARY SYNTHESIS... 

Polymer-assisted solution-phase synthesis offers strategies for chemical library construction that complement solid-phase methods. Tools now available include chemoselective sequestering resins, bifunctional solution-phase linking reagents, bifunctional chemically tagged reagents, and an... 

During the past few years, polymer-assisted solution-phase synthesis has become the prevalent method for the parallel synthesis of chemical libraries as confirmed by the increasing number of publications and reviews on the subject.16-29 A key step in the parallel solution-phase combinatorial... 

Since the experimental conditions for the traditional Biginelli reaction are quite straightforward, small libraries of DHPMs are readily accessible by parallel synthesis. Along these lines the generation of a 140-member single compound DHPM library by combination of 25 aldehydes, 6 ureas/thioureas, and 7 acetoacetates or acetoamides under standard reaction conditions has been reported [123, 124]. More rapid approaches make use of microwave-enhanced solution-phase protocols [88, 89, 125]. Apart from these conventional solution-phase methods, it is also possible to employ polymer-supported reagents to aid in the purification and workup protocol. Polymer-assisted solution-phase chemistry using polymer-supported... 

Polymer-supported Synthetic Methods - Solid-phase Synthesis (SPS) and Polymer-assisted Solution-phase (PASP) Synthesis... 

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