Quinoxaline resin

The quinoxaline resin was provided by F. Arnold of Materials Laboratory. The synthesis of this resin has been described elsewhere (5). The sulfone resin was synthesized by Gulf Research and Development Co. (9). This batch of resin is labelled as ATS-6. 

Figure 1 shows the TICA scan results of the quinoxaline resins from 0°C up to 390°C. Figure la shows the scan under nitrogen environment and Figure lb shows a similar scan in air. 

Figure 1 shows that the air and nitrogen environments do not change the vitrification temperature of the quinoxaline resin. 

The higher uncured Tg of the quinoxaline resin requires a lower extent of reaction to reach the vitrification point during the scan. The cumulative effect at vitrification may not be sufficient to show different vitrification temperatures. 

Figure 4. Time to vitrification of the quinoxaline resin as a function of temperature.

Figure 10. Temperature scan of the quinoxaline resin after curing in nitrogen at 200 for 1 hour. The scan down curves show the final Tg is above the experimental temperature (390 C).

Figure 17. Temperature scan of the quinoxaline resin after exposing to nitrogen and air at 380 C. After post curing in nitrogen, the glass transition temperature remained unchanged. However, after curing in air, there was no observable Tg.

Perhydropyrido[l, 2-a]pyrazine-1,6-diones and 6a,7,8,9-tetrahydro-5//-pyrido[l,2-a]quinoxaline-6,10-diones were formed when their precursors bond to a resin were cleaved by an acid (01MIP4). 

Depending on the reaction temperature and reaction time, tetrahydroisoquinoline 357 afforded different mixtures of 1,2,3,4,11,11 a-hcxahydro-6//-pyrazino[ 1,2-3]isoquinolines 358-361 and tetracyclic compound 362 (Scheme 30) <2005JA16796>. Each of the individual diastereoisomers 358-361 could be transformed into the compound 362. z7r-3//,4a//-3-Phcnylpcrhydropyra/ino[ 1,2-7]isoquinoline-l,4-dione was prepared via automated parallel solid-phase synthesis on Kaiser oxime resin <1998BML2369>. l,2,3,5,6,7-Hexahydropyrido[l,2,3-r/f ]quinoxaline-2,5-dionc was obtained by catalytic hydrogenation of ethyl 3-(2-oxo-l,2,3,4-tetrahydro-5-quinoxalinyl)acrylate in the presence of TsOH over 5% Pd/C catalyst under 40 psi of hydrogen <1996JME4654>. 

In the absence of sodium bisulfite, aqueous glyoxal solutions react with o-phenylenediamine to give only about 30% yields of quinoxaline together with large quantities of resinous by-products. Therefore, if an aqueous glyoxal solution is to be used in this preparation it should be mixed with a water solution of. two molar equivalents of sodium bisulfite before it is added to the o-phenylenediamine solution. 

After hydrolyzate acidification with hydrochloric acid at pH values lower than 1, quinoxaline-2-carboxylic acid is quantitatively extracted into ethyl acetate, chloroform, or dichloromethane, since at these strongly acidic conditions the ionization of their carboxylate moiety is suppressed (pK, 2.88), and then back-extracted into aqueous buffered solutions at pH 6.0 or higher. These liquid-liquid partitioning procedures isolate quinoxaline-2-carboxylic acid from a complex mixture of tissue hydrolysates, and provide an aqueous extract suitable for further purification by solid-phase extraction. This has been accomplished either with the strong cation-exchange resin AG MP-50 (419, 420) or with a polar silica column (422). 

PB PBI PBMA PBO PBT(H) PBTP PC PCHMA PCTFE PDAP PDMS PE PEHD PELD PEMD PEC PEEK PEG PEI PEK PEN PEO PES PET PF PI PIB PMA PMMA PMI PMP POB POM PP PPE PPP PPPE PPQ PPS PPSU PS PSU PTFE PTMT PU PUR Poly(n.butylene) Poly(benzimidazole) Poly(n.butyl methacrylate) Poly(benzoxazole) Poly(benzthiazole) Poly(butylene glycol terephthalate) Polycarbonate Poly(cyclohexyl methacrylate) Poly(chloro-trifluoro ethylene) Poly(diallyl phthalate) Poly(dimethyl siloxane) Polyethylene High density polyethylene Low density polyethylene Medium density polyethylene Chlorinated polyethylene Poly-ether-ether ketone poly(ethylene glycol) Poly-ether-imide Poly-ether ketone Poly(ethylene-2,6-naphthalene dicarboxylate) Poly(ethylene oxide) Poly-ether sulfone Poly(ethylene terephthalate) Phenol formaldehyde resin Polyimide Polyisobutylene Poly(methyl acrylate) Poly(methyl methacrylate) Poly(methacryl imide) Poly(methylpentene) Poly(hydroxy-benzoate) Polyoxymethylene = polyacetal = polyformaldehyde Polypropylene Poly (2,6-dimethyl-l,4-phenylene ether) = Poly(phenylene oxide) Polyp araphenylene Poly(2,6-diphenyl-l,4-phenylene ether) Poly(phenyl quinoxaline) Polyphenylene sulfide, polysulfide Polyphenylene sulfone Polystyrene Polysulfone Poly(tetrafluoroethylene) Poly(tetramethylene terephthalate) Polyurethane Polyurethane rubber... 

Polymers containing heterocycles in the backbone include a variety of compounds, as the diversity of heterocyclic molecules is quite large. The polymers from this class may contain groups derived from furan, thiophene, pyrrole, isoindole, benzimidazole, benzothiazole, benzoxazole, quinoxaline, etc. Macromolecules with a ladder backbone containing, for example, a phenoxazine unit in their structure also are known. Amino thermosetting resins from melamine can be considered as polymers containing heterocycles in their structure. 

Quinoxaline synthesis. Condensation of glyoxal bisulfite with o-phenylenediamine in aqueous solution at about 80° affords quinoxaline in high yield, and this base on permanganate oxidation affords 2,3-pyrazinedicarboxylic acid. In the absence of sodium bisulfite, aqueous glyoxal reacts with o-phenylenediamine to give quinoxaline in only about 30% yield along with resinous by-products. 

A family of acetylene-terminated phenyl quinoxalines have been synthesized by the Polymer Branch of the Materials Laboratory. ( 1) These phenyl quinoxalines are remarkable for their thermooxidative stability and resistance to moisture. These materials have potential for structural applications as adhesives or composite matrix resins.(2) The feature of moisture resistance makes the materials especially attractive for bonding aluminum. However, problems arise from the fact that aircraft aluminum alloys (and their surface oxiges) are altered by exposures to temperatures above 177 C (350 F) and this is much lower than the polymerization temperatures of the acetylene-terminated oligomers. 

Filippone and co-workers reported a resin-bound synthesis of quinoxalines <01HCA2379> using both Wang and Merrifield resins. Polymer-bound 3-diazenylbut-2-enoates 246 reacted readily with substituted 1,2-phcnylenediamincs 247 to afford polymer-bound quinoxalines 250 through intermediates 248 and 249. Final products were cleaved by treatment with MeONa in MeOH/THF to afford 251. 

Other quinoxaline-type polymers can have higher Tg values, e.g. 400°C. DGEBA stands for diglycidyl ether of bisphenol A. Epoxy resin properties can depend considerably on the hardener used. 

Manuf by oxidn. of acetaldehyde or ethylene glycol. Intermed. in synth. of quinoxalines and quinones. Monomer for glyoxal resins. Disinfectant for surgical instruments. Yellow prisms, dl 1.29. 

Ghosh P, Mandal A (2012) Synthesis of functionalized benzimidazoles and quinoxalines catalyzed by sodium hexafluorophosphate bound Amberlite resin in aqueous medium. Tetrahedron Lett 53 6483-6488... 

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