Condensation synthesis

Fig. 13. Polymerization chemistry of phenol—formaldehyde condensation synthesis of novolac resia. The phenol monomer(s) are used ia stoichiometric excess to avoid geUation, although branching iavariably occurs due to the multiple reactive sites on the aromatic ring.

Synthesis. The first hiUy alkyl/aryl-substituted polymers were reported in 1980 via a condensation—polymeri2ation route. The method involves, first, the synthesis of organophosphine-containing alkyl or aryl substituents, followed by the ready oxidation of the phosphine to a phosphorane with leaving groups suitable for a 1,2-elimination reaction. This phosphorane is then thermally condensed to polymers in which all phosphoms atoms bear alkyl or aryl substituents. This condensation synthesis is depicted in Eigure 2 (5—7,64). 

CLAISEN - GEUTER - OIECKMANN Ester condensation Synthesis ot open chain or cyclic p keloesters by aldol type condensation... 

Faggi C, Marcaccini S, Pepino R, Pozo MC (2002) Studies on isocyanides and related compounds synthesis of l,4-benzodiazepine-2,5-diones via Ugi four-component condensation. Synthesis 18 2756-2760... 

The effect of hydrophobicity of some ionic liquids was explored (119) in a recent example of a condensation synthesis involving a quaternary ammonium amide. The water produced was continuously removed from the reaction mixture, producing a much higher yield than had previously been possible for this reaction in other media. 

Ellison RA, Lukenbach ER, Chiu C-W (1975) Cyclopentenone synthesis by aldol condensation. Synthesis of a key prostaglandin intermediate. Tetrahedron Lett 16 499-502... 

An additional entirely selective condensation synthesis for asymmetric TTF molecules is based on strategy S6, which consists in the reaction of an organotin dichalcogenolate with an ester in the presence of a Lewis acid such as MesAl (Yamada et al, 2004). A scheme of the reaction is given in Fig. 2.7. The method applies to the preparation of varied asymmetric IT Fs and can also be extended to the synthesis of selenium-containing analogues. 

C.-H. Lin, T. Sugai, R. L. Halcomb, Y. Ichikawa, and C. H. Wong, Unusual stereoselectivity in sialic acid aldolase-catalyzed aldol condensations Synthesis of both enantiomers of high-carbon monosaccharides, J. Am. Chem. Soc. 774 10138 (1992). 

The process of glycosyl transfer, defined in this mechanistic way, extends to hydrolysis and its reverse (i.e., condensation synthesis from glycoses with expulsion of water) as well as to reactions in which water is not a reactant. However, the terms glycosyl transfer and transglyco-sylation are bound to the group transfer concept and inevitably carry a... 

An alternative type of condensation synthesis involves the decomposition of organophos-phorus azides. First reported by Haber and coworkers in the 1960s,61 these syntheses follow the pathway shown in reaction (24), in which elimination of nitrogen takes place in solution with the direct formation of either a cyclic phosphazene or a polymer. Matyjaszewski and coworkers62 have used this method to produce the nearly insoluble (NPPh2) , which is difficult to prepare by other approaches, and [NP(Ph)(p-MePh)] which is soluble in aromatic solvents. However, phosphorus azides are potential detonators, and they must be prepared and used in solution and not isolated in the solid state. 

The only claim of direct evidence for the intermediates proposed above come from ESR measurements subsequent to photolysis of Mn2(CO)j0 in tetrahydrofuran at room temperature.112) A long-lived, ESR detectable, radical was found and proposed to be Mn(CO)5 THF. The intermediate disappears upon addition of I2 and the formation of Mn(CO)sI is observed. These data seem to be wholly consistent with the photochemistry outlined above, but the interpretation of the ESR signal as that due to an Mn(CO)s moiety seems untenable because it is too long-lived. The Re(CO)s species proposed as an intermediate in the photolysis of Re2(CO)10 has recently been synthesized by atom/ligand co-condensation synthesis and infrared data in the matrix at low temperature support a square-pyramidal structure.113) An ESR signal was also observed from a species thought to be Mn(CO)s formed by subliming Mn2(CO)i0 on to a cold tip.114) The ESR detectable species is now believed to be OOMn(CO)s.115)... 

Scheme 2. Condensation synthesis of pentaphenyl-Cp from diphenylacetylene (tolane) and benzal chloride. Yields are 24-51% (42).

In addition, Song et al. (76) used a one-step condensation synthesis method to prepare the PLA-MWCNTnanocomposites. For detailed experimental conditions, refer to Song et al. (76). The nanocomposites were prepared using pure and carboxylic-acid-functionalized MWCNTs. As with the other studies, the carboxylic-acid-functionalized MWCNTs dispersed better in PLA compared with non-functionalized MWCNTs. Overall, it can be inferred from the studies described in this section that the functionalization of MWCNTs is a very important step in the process of making a nanocomposite, as it will help to disperse the nanotubes uniformly, which will eventually create the superior properties of the resulting nanocomposite. In addition, among the currently available methods for functionalization, carboxylic-functionalization is the best for uniform dispersion. 

SCHEME 119. Chiral enolate directing aldol condensation synthesis of Hapalosin573... 

Templated mesoporous silica materials have been discovered by Kresge et al. in 1992 [ 1,2]. S ince then, efforts have been made to produce by direct co-condensation synthesis hybrid materials functionalized by different types of reactive groups. 

Keywords process condensate synthesis of mass exchange network multicomponents total annualized cost. 

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