Multicomponent combinatorial approach

In asymmetric catalysis, Sharpless emphasized the importance of ligand-accelerated catalysis through the construction of an asymmetric catalyst from an achiral precatalyst via ligand exchange with a chiral ligand. By contrast, a dynamic combinatorial approach, where an achiral precatalyst combined with several multicomponent chiral ligands (L, -----) and several chiral activator ligands... 

In view of the multicomponent nature of the tandem [4 + 2] / [3 + 2] cycloaddition, the potential for a combinatorial approach to the synthesis of nitroso acetals has been investigated on solid-phase supports. The incorporation of either the dipolarophile or the starting nitroalkene on a Wang-type resin is compatible with the tandem cycloaddition promoted at high pressures (Schemes 2.28 and 2.29). The solid-supported nitroso acetals are subsequently liberated (in moderate yields from the staring nitroalkene) upon the addition of a catalytic amount of potassium cyanide in triethylamine and methanol or by reduction with lithium aluminum hydride (LAH) (261,264). 

From an economic viewpoint, the classical determination of alloy phase diagrams is a laborious process, involving alloy preparation and heat treatment, compositional, structural, and microstructural analysis (and, even then, not yielding reliable phase boundary information at low temperatures due to kinetic limitations). While this investment is justified for alloys of major technical importance, the need for better economics has driven an effort to use alternative methods of phase discovery such as multiple source, gradient vapor deposition or sputter deposition followed by automated analysis alternatively, multicomponent diffusion couples are used to map binary or ternary alloy systems structurally and by properties (see Section 6). These techniques have been known for decades, but they have been reintroduced more recently as high-efficiency methodologies to create compositional libraries by a combinatorial approach, inspired perhaps by the recent, general introduction of combinatorial methods in chemistry. 

Much has been made of combinatorial approaches to materials discovery however, there are many barriers to the introduction of these methods to SOFC materials, not least their suitability to synthesize libraries of complex multicomponent oxides, such as the cathode materials Lai xSrxCoi yFey03 s [45], In addition to these limitations, there is the... 

Tempos, A., Hegedus, M., Margitfalvi, J.L., Szabo, E.G. and V gvdri, L. (2008). Multicomponent Au/MgO catalysts designed for selective oxidation of carbon monoxide Appication of a combinatorial approach. Appl. Catal. A General 334, 1-2, 348-356. 

In principle, the broad range of functional monomers eurrently available makes it possible to design an MIP specific for any type of stable ehemical compound. Currently the selection of the best monomers for polymer preparation is one of the most crucial issues in molecular imprinting. Thermodynamic calculations and combinatorial screening approaches olfer possible solutions, and have already been used successfully for predicting polymer properties and for the optimization of polymer compositions (see Ref. 9,57,58, and Chapter 8), however, in practical terms, application of these methods is not trivial. The problem lies in the technical difiiculty of performing detailed thermodynamic calculations on multicomponent systems and the amount of time and resources required for the combinatorial screening of polymers. To check a simple two-component combination of 100 monomers, for example, one has to synthesize and test more than 5000 polymers, a very difiicult task. This task will be further complicated by the possibility that these monomers could be used in monomer mixtures in dilferent ratios. 

After experimentally confirming the validity of this idea, the principal authors attempted to use this approach for explanation of the so-called miscibility windows (Paul and Barlow 1984). The latter term refers either to polymer/copolymer blends that show miscibility only within a limited range of copolymer compositions (e.g., Balazs et al. 1985 Fernandes et al. 1986 Goh and Lee 1987) or to blends of two copolymers having a common monomer (Shiomi et al. 1986). As earlier, in Koningsveld s treatment of Xii, here also the parameter B has an enthalpic contribution and a non-combinatorial entropic contribution. For multicomponent systems, Eq. 2.47 can be generalized (Barlow and Paul 1987) ... 

Another approach that has been used in combinatorial chemistry is the use of a one-pot reaction such as the well-known Ugi multicomponent reaction " and the Passerini reaction. Multicomponent reactions are reactions in which three or more reactants come together in a single reaction vessel to form a new product that displays aspects of all the components. The reactions may be carried out in solution or on a solid support. ... 

---