Multicomponent method

A number of microwave-assisted multicomponent methods for the synthesis of imidazoles have been reported [68-71 ]. The irradiation of a 1,2-diketone and aldehyde with ammonium acetate in acetic acid for 5 min at 180 °C in a single-mode reactor provides alkyl-, aryl-, and heteroaryl-substituted imidazoles 39 in excellent yield (Scheme 14) and this method has been used for the rapid and efficient preparation of two biologically active imidazoles, lepidiline B and trifenagrel [68]. 

It is customary in analytical chemistry to examine unknown samples by a screening procedure using a multicomponent method like OES or MS in case of inorganic constituents on the one hand and GC or HPLC in case of organic constituents on the other. In this way, an overview can be obtained on the type of constituents and their approximate contents. In many cases it is necessary to get a deeper insight into the sample composition. For this reason, the one or a few constituents have to determine more precisely. 

On the other hand, not only the enormous number of signals in multicomponent methods but also the large number of species that can be detected in highly resolved spectra and chromatograms, respectively, influence the information amount. Therefore, Matherny and Eckschlager [1996] proposed the introduction of so-called relevancy coefficients, k, into the system of information-theoretical assessment. In analytical practice, the coefficients k can be considered as being weight factors of the information contents of the respective species with which Eq. (9.21) becomes... 

The group of Borrell has described a variety of different microwave-assisted approaches to biologically active pyrido[2,3-d]pyrimidin-7(8H)-ones [441-443]. In the multicomponent method outlined in Scheme 6.254a, the target structures were... 

For some applications, one may use very simple approximations to the calculation of transport properties, that evaluate mixture properties from pure species properties via certain mixture averaging rules. However, we more often encounter applications in which the approximate averaging rules are not adequate, and multicomponent methods are necessary [103,178],... 

To design complex distillation columns, multicomponent methods are used. The true boiling curve is replaced by an approximate stepwise representation as a shown in Figure 12.18. Each step represents a pseudocomponent with a boiling point as indicated and a fraction of the total feed mixture based on the length of the horizontal portion of the step. 

Burnt gas composition using either dedicated single-species analyzers or multicomponent methods such as Fourier transform infrared analyzer (FTIR) and mass spectrometer (MS) and... 

Approximate multicomponent methods (chapter 12) Fenske-Underwood-4jilliland Group method... 

Rigorous multicomponent methods (Chapter 15) Bubble-point method (Wang-Henke)... 

Due to the fact that complexing results in multiple anions and/or cations, activity coefficients for such species must be calculated using multicomponent methods even for simple binary solutions. The methods presented in Chapter V are suitable for use. 

Orru and Ruijter developed an efficient palladium-catalyzed multicomponent method toward 4-aminophlhalazm-1 (2H)-ones 11 (Scheme 3.10), combining isocyanides, hydrazines, and 2-halobenzoates in an extremely fast and regioselective reaction that proceeds via isocyanide insertion followed by lactamization. Although the scope with regard to the isocyanide and the hydrazine is limited, a simple dealkylation procedure affords the unprotected products, which can be further derivatized [23]. 

As a conclusion, much research has been done in these particular three (four)-multicomponent methods, which allows the efficient synthesis of very interesting products. But there is still room to improve them, especially in the case of the asymmetric versions of the two of them. 

Alizadeh A, Zohreh N (2009) A novel multicomponent method for the synthesis of 2-thioxo-l,3-thiazolidine -ones. Synlett 2009 2146-2148... 

A report in 2005 by Black and Arndtsen [106a] who reported a copper-catalyzed multicomponent method that leads to a-substituted amides using acid chlorides with organostannanes (Figure 1.29). 

Figure 1.29 Some of the results reported by Black and Arndtsen [106b] for the copper-catalyzed multicomponent method to a-substituted amides.

Besides the identification of components of a mixture, the use of GC-MS systems to determine the concentration of target compounds according to legal requirements is a primary apphcation in governmental, industrial as well as private control labs. The need to determine quantitatively an increasing number of components in complicated matrices in ever smaller concentrations makes the use of GC-MS systems in routine analysis appropriate for economic reasons. Gone are the days when only positive results from classical GC were confirmed by GC-MS. In many areas of trace analysis, the development of routine multicomponent methods has become possible only through the selectivity of detection and the specificity of identification of GC-MS and GC-MS/MS systems. The development of GC-MS data systems has therefore been successful... 

S. Rostamnia, A. Zabardasti, SBA-15/TFE (SBA-15/2,2,2-trifluoroethanol) as a suitable and effective metal-free catalyst for the preparation of the tri- and tetra-substituted imidazoles via one-pot multicomponent method, J. Fluorine Chem. 144 (2012) 69-72. 

A new cascade reaction of isocyanides, chromone 3-carboxylic acid (311), and nucleophiles (ROH, RNH2, and NaN3), catalysed by Sc(OTf)3 under microwave irradiation, has been developed as a multicomponent method for the preparation of chromone-2-carboxamides and chromone-2-carboxamido-3-esters (313). The sequence apparently commences by the Michael addition of RN=C to generate intermediate (312). ° ... 

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