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Heterocyclic cross-link

Cross-linked, heterocyclic esters (28) of cellulose may be obtained... [Pg.356]

Cyanate/Cyanurate. When aryl cyanate esters are heated to 150 to 250°C, they cyclotrimerize to cyanuric acid esters (Fig. 3.62). They can be catalyzed by organo-metallic and active hydrogen compounds. When the monomer is a dicyanate such as bisphenol A dicyanate (Fig. 3.63), the result is a highly cross-linked heterocyclic polymer (Table 3.57). Using a novolac polycyanate has produced Tg and useful life over 300°C. [Pg.182]

A considerable number of non-cross-linked aromatic and heterocyclic polymers has been produced. These include polyaromatic ketones, aromatic and heterocyclic polyanhydrides, polythiazoles, polypyrazoles, polytriazoles, poly-quinoxalines, polyketoquinolines, polybenzimidazoles, polyhydantoins, and polyimides. Of these the last two have achieved some technical significance, and have already been considered in Chapters 21 and 18 respectively. The most important polyimides are obtained by reacting pyromellitic dianhydride with an aromatic diamine to give a product of general structure (Figure 29.17). [Pg.847]

DNA cross-linking agents (mainly heterocycles) as antitumor drugs 98CRV2723. [Pg.232]

Natural and synthetic heterocycles as DNA cross-linking agents and antitumor drugs 98CRV2723. [Pg.233]

The ready alkylation of heterocyclic thiols lends this link to applications in solid-phase synthesis. Although much more work has been done in other heterocyclic systems, a prototype solid-phase synthesis has been described in which the pteridine is built from a 2- or 4-alkylthiopyrimidine attached to a cross-linked polystyrene support <20030BG1909, 2003TL1267> Oxidative cleavage was preferred using DMDO to avoid unwanted by-products... [Pg.926]

Diketene also is widely employed as a natural and synthetic fiber cross-linking agent, wood preservative and paper-sizing agent. Both it and /3-propiolactone have wide application as chemical intermediates. The synthetic applications of diketene for the synthesis of aromatic, heterocyclic and aliphatic compounds is exceptionally extensive (74ACR265). [Pg.402]

Antisera to cloxacillin/oxacillin/dicloxacillin and cefuroxime were also produced by similar procedures and successfully utilized in methods for the detection of these antibiotics in milk (34). Unfortunately, a number of other -lactams including aminopenicillins and some cephalosporins were not amenable to this mixed anhydride procedure. Thus, a carrier protein derivatization procedure was used to allow cross-linking of cephalosporins, such as cephataxime that has an acetoxy side chain, to ovalbumin. Because acetoxy groups react readily with the heterocyclic nitrogen atoms, the latter were introduced into ovalbumin through the carbodiimide-mediated derivatization of protein carboxyl groups with amino-methylpyridine (34). [Pg.837]

Reissert compounds (l-acyl-l,2-dihydro-2-quinolinecarbonitriles) have been prepared on cross-linked polystyrene and C-alkylated in the presence of strong bases (Entry 8, Table 15.25). Treatment of polystyrene-bound C-alkylated Reissert compounds with KOH leads to the release of isoquinolines into solution (Entry 9, Table 15.25). The reaction of support-bound quinoline- and isoquinoline /Y-oxides with acy-lating agents followed by treatment with electron-rich heteroarenes and enamines has been used to prepare alkylated and arylated derivatives of these heterocycles (Entry 10, Table 15.25 see also Table 15.26). [Pg.434]

Ala. The action of lysyl oxidase to produce allysine allows three of these modified residues to condense with one lysine residue to form the heterocyclic complex amino acid desmosine. which cross-links two or even three chains. A highly cross-linked network results. [Pg.126]

The combination of resonance stabilization in the melamine heterocycle, and the high cross-linking between methylol melamines and with the other polymers, all produce the outstanding properties which make it a valuable specialty member of the thermoset plastics spectrum. [Pg.662]

Substituents on aromatic rings and heterocycles that take part in intermolecular cross-linking, or intramolecular cyclization reactions, reduce the rate of release of volatile products and increase the yield of the carbonized residue. Otherwise, the contribution of the substituents to the coking process is small. The substituents are often split off and removed as volatile products, the thermal stability of the polymers being thereby reduced. [Pg.206]

An unusual feature of their sarcophaginate frameworks is the structure of the cap the amidine and amide fragments are cross-linked with a methylene unit to form a near-planar diazine heterocycle fused to the cap as a subsidiary feature [126]. [Pg.148]


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See also in sourсe #XX -- [ Pg.196 ]

See also in sourсe #XX -- [ Pg.196 ]




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Heterocyclic linked

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