Monofunctional substrates

Normally, transesterif Icat ions are acid- or base-catalyzed, e.g., sulfuric acid, p-toluenesulfonic acid, and potassium or sodium alkoxides in the appropriate alcohols. These methods fail with molecules containing acld-or base-labile functional groups. The titanate-mediated esterifications, deacylations, and transesterifications of rather simple, monofunctional substrates are described in the patent literature see the references in a recent article. Recently, Seebach, et al. 4 have demonstrated that this method is applicable also to substrates with additional functional groups... 

Para-t-butylphenyl glycidyl ether BPGE had a similar viscosity and C/O ratio as those of NA and had the best properties of the photocurable epoxies that were surveyed, but this monomer dewetted from Si substrates immediately after spin coating and formed a puddle at the substrate center. Other monofunctional epoxies exhibited the same behavior. Mixtures of BPGE with multifunctional aromatic epoxies wetted Si substrates and could be used as planarizing layers. 

To date, only a few iridium catalysts have been applied to industrially relevant targets, especially on the larger scale. It is likely that several types of Ir catalyst are, in principle, feasible for technical applications in the pharmaceutical and agrochemical industries. At present, the most important problems are the relatively low catalytic activities of many highly selective systems and the fact, that relatively few catalysts have been applied to multifunctional substrates. For this reason, the scope and limitations of most catalysts known today have not yet been explored. For those in academic research, the lesson might be to employ new catalysts not only with monofunctional model compounds but also to test functional group tolerance and-as has already been done in some cases-to apply the catalysts to the total synthesis of relevant target molecules. 

As these reactive oligomers have a high viscosity, they are diluted with a multifunctional and if necessary a monofunctional acrylate monomer. The acrylate monomers reduce the viscosity of the mixture for easier application on substrates. The multifunctional acrylate monomers increase the crosslink density the monofunctional monomers decrease it. 

The monofunctional epoxy diluents are essentially chain stoppers since they inhibit crosslinks from forming. The extent to which the cured properties are affected is directly dependent on the concentration of the diluent added to the epoxy resin. The general effect is to reduce viscosity and improve the impact and thermal shock resistance while slightly reducing the thermal resistance. The thermal expansion of the cured resin is increased, as it is also with nonreactive diluents. This can lead to internal stress on the bond line depending on the thermal expansion of the substrate material. 

Molecules of type I are the classical product of reactions between monofunctional reactants. In many cases, they can be considered to be derived from the functionalization of a substrate or, reciprocally, of an amine, in order to attach chemical moieties purposely designed for specific uses, without substantially affecting the essential molecular structure. This is the case, for instance, of the antibiotic substance 494, which assumes hydrophilic properties upon aminomethylation of the pharmacologically active substrate having an amino acidic residue, or of the complexant agent 495,- as well as of the polyacrylamide Mannich base 502. - ... 

The reaction is usually carried out by mixing the reactants in equimolar amounts. In some cases, however, amine and aldehyde are allowed to react first and then combined with the substrate. No general rule concerning the choice of reagents and reaction conditions exists however, the very laige number of experimental methods reported in the literature can be divided into a number of main groups, as summarized in Table 6, where the synthetic methods predominantly applied to each individual substrate class are listed. Only monofunctional reactants are taken into coasideration here, as the presence of different reactive centers involves the possibility of selective reactions that have to be... 

Thioaroylcarbamates are readily prepared compounds which react as monofunctional compounds with aminophenols without addition of an add or a base [2899]. Cyanohydrins can provide the 2-carbon atom of this ring when aminophenols are substrates, and a second molecule of aminophenol is attached at C-2 methyl group [3705, 3707). 

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