Trifunctional compounds

Open-chain trifunctional compounds containing no other elements than... 

Hydrophilic short biotin-PEG tags also have found their way into the design of multifunctional crosslinkers to study protein structures by mass spec. Fujii et al. (2004) developed a homobifunctional NHS ester crosslinker that in addition has a PEG-biotin handle (Figure 18.1). The reagent actually is a trifunctional compound similar to the biotinylated PIR compound... 

Title Trifunctional Compound, Composition and Polymer Thereof... 

Heteroelectrophiles like dimethyl disulfide (entries 9, 18, 29) lead to trifunctional compounds. A second methoxycarbonyl group can be introduced with methyl chloro-formiate (entries 38, 42). However, the trimethylsiloxy compounds are extremely sensitive and undergo very fast ring opening to malonic ester derivatives 61). 

There are two reasons for this. First, the Sharpless epoxidation can be applied to almost all primary and secondary allyl alcohols. Second, it makes trifunctional compounds accessible in the form of enantiomerically pure a,/1-epoxy alcohols. These can react with a wide variety of nucleophiles to produce enantiomerically pure second-generation products. Further transformations can lead to other enantiomerically pure species that ultimately may bear little structural resemblance to the starting a,/3-epoxy alcohols. 

This condensation works best if the ester has no a hydrogens, so that it cannot form an enolate. Because of the difference in acidities, however, the reaction is sometimes successful between ketones and esters even when both have a hydrogens. The following examples show some crossed Claisen condensations between ketones and esters. Notice the variety of difunctional and trifunctional compounds that can be produced by appropriate choices of esters. 

On the basis of these studies, a tetrafunctional silyl enol ether (18) carrying four such enolate functions has been prepared the corresponding trifunctional compound is also available [142]. These silyl enolates effectively couple living poly(vinyl ethers) with the chloride counteranion to form tri- and tetraarmed polymers (e.g., 19, Scheme 10) [205]. Similar chemistry also operates with living cationic poly(a-methylstyrene) but specifically needs the additional use of an amine to accelerate the release of the trimethylsilyl groups [159,207]. 

Fig. 13-5. Schemes for the reactions involving three odd-electrons (a) the electron transfer reaction of triplet 10-methylphenothiazine ( D ) with 4-(4-cyanobenzoyloxy)TEMPO ( A-Ri ) in 2-propanol at 293 K and (b) the reactions of triradicals generated by photolysis of benzophenone(BP)-dipheylmethane(DPM)-nitroxide(R2 ) trifunctional compounds at 293 K. (Reproduced from Ref. [15] by permission from The Japanese Chemical Society)...

The functionality of alkoxy groups at the silicon allows us to localize the probe in the polymer. Trifunctional compounds are located at the network junction of a crosslinked poly-dimethylsiloxane while bifunctional probe molecules are placed on the main chain during polymer formation. 

Next to side-chain LCPs and main-chain LCPs, supramolecular networks were obtained by complex-ation of bipyridines with polyacrylates containing pendant benzoic acid groups. In a related approach, Kato and Frechet have studied supramolecular networks based on low-molecular-weight components, in which a trifunctional benzoic acid derivative was combined with a difunctional pyridine derivative.62 The hierarchy of the LC-phase that was formed turned out to be dependent on the flexibility of the trifunctional compound used. 

If a trifunctional compound (triethanolamine) is reacted with a difunctional diisocyanate (for example TDI), in order to avoid undesired crosslinking, formation of big particles or high viscosities, the molar ratio between TDIrTEOA is usually less or equal to 1 1. For high solid content, lower TDIrTEOA ratios (around 0.6 1), are used. 

Due to their zwitterionic character, the amino acids are difficult to convert quantitatively and uniformly into suitable GC derivatives. Numerous methods have now been reported toward meeting this difficult goal. From the 19 amino acids contained commonly in protein hydrolyzates, the trifunctional compounds are particularly difficult to handle in a quantitative fashion. The problems here result from a different reactivity of various fimctional groups as well as only a limited solubility of certain amino acids in the reaction media. 

Fig. 16. Smectic network formation by supramolecular self-assembly of trifunctional compound 47 and bifunctional bipyridine 4 or 9...

When p-nadimidochlorobenzene as a monofunctional dichloro compound is added to the reaction mixture of sulfide and aromatic dichloro compound, an end capped oligomer with a pendant double bond is obtained. Further, a trifunctional compound, such as trichlorobenzene, may be added to compensate the monofunctional compound with respect to molecular weight. OUgomers with a molecular weight of 1,000-6,000 Dalton can be readily obtained. The oligomerization is achieved at 225-260 C. At this temperature, the double bonds are still not reactive. 

Table 11.1 Typical di- and trifunctional compounds used for photocuring.

The copolymerization is conducted either at low pH with the acid-form monomers, which are neutralized after pol5unerization, or at roughly neutral pH with partially neutralized carboxylate salts. Sodium hydroxide and sodium carbonate typically are the neutralizing agents. The cross-linkers vary in fimctional-ity, from difiinctional acrylate esters and methylenehisacrylamide, to trifunctional compounds, such as 1,1,1-trimethylol-propanetriacrylate and triallylamine, and to tetrafunctional compoimds, such as tetra(allyloxy)ethane. 

The formation of aromatic isocyanate trimers is of economic importance, because rigid insulation foams, having isocyanurate structures built into their network structure, are produced from aromatic diisocyanates. Triphenyl isocyanurates with hydroxyl or carboxyl groups in their p-positions can be obtained on hydrolysis of McsSiO- and McsSiOCO-groups, respectively, with hydrochloric acid °. Such trifunctional compounds are of use in the construction of network polymers. The mechanism of the phenyl isocyanate trimer-ization, using Pd(o) diimide catalysts was elucidated recently. The initial steps of this trimerization reaction involve a chain growth process as encountered in the anionic homopolymerization of isocyanates. 

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