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1
Kleinhans, Dewald Johannes. "Studies in the synthesis of benzoxazole compounds." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/97900.
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Thesis (PhD)--Stellenbosch University, 2015.ENGLISH ABSTRACT: Benzoxazoles are an important class of π-electron-excessive, benzene-fused heterocyclic compounds found in natural products and display a wide range of pharmacological applications. It is therefore a widely used starting scaffold for drug and agrochemical discovery programs. Other applications include: chiral auxiliaries in asymmetric reactions, chiral receptors for the resolution of racemic mixtures, fluorescent whitening dyes, various photochromic materials and as ligands for a wide range of catalytic reactions. Due to our interests in resorcinarenes, we came across 4-hydroxybenzoxazoles, a structural motif that has not been explored as potential asymmetric ligands. In this thesis it was attempted to investigate the synthesis, functionalisation and coordination chemistry of these compound class and finally look at a method of synthesising chiral 4-hydroxybenzoxazoles from amino acids. A small library of achiral 4-hydroxybenzoxazoles were synthesised in good yields. These compounds were then reacted with various transition metals, of which only the Pd-salts proved to return any usable compounds. The first structural evidence of the bonding of 4- hydroxybenzoxazoles was recorded from single crystal X-ray diffraction analysis of the coordination compounds that formed. Different coordination modes were recorded, depending on the ligand and the Pd-salt used. The PdCl2 compounds were also tested for catalytic activity with a Heck reaction, showing good conversions for the reaction between iodobenzene and styrene to form stilbene. Further examination pointed to the ligands playing an insignificant role in the reaction and the products possibly due to only the PdCl2’s reactivity. During this period it was also attempted to functionalise the phenol group with P(III) groups and repeat the coordination and catalytic studies. Efforts to synthesise these compounds were not successful, with oxidation of the P(III) to P(V) groups or degradation of these compounds. Efforts to synthesise these via phosphorous protection, utilising BH3 or the in situ trapping of the compounds with transition metals, were also not successful. During the trapping experiments the phosphinite and Pd-salt formed a re-arranged product that is a known and useful catalyst on its own. Finally a small library of chiral benzoxazoles and 4-hydroxybenzoxazoles were synthesised, starting from amino acids and utilising a Mitsunobu reaction to perform the ring closing. Antimicrobial tests with these compounds did not return any appreciable results.
AFRIKAANSE OPSOMMING: Bensoksasool is 'n belangrike klas van π-elektron-ryk, benseen-saamgesmelte heterosikliese verbindings wat in natuurlike produkte voorkom en 'n wye verskeidenheid van farmakologiese funksies vertoon. Dit is dus 'n baie algemene basis struktuur vir dwelm- en landbouchemiese ontdekkings programme. Ander gebruike sluit in: chirale ligande in asimmetriese reaksies, chirale reseptore vir die resolusie van rasemiese mengsels, fluoresserende verwittings kleurstowwe, verskeie fotochromiese materiaal en as ligande vir 'n wye verskeidenheid van katalitiese reaksies. As gevolg van ons belangstelling in resorsinarene, het ons op 'n strukturele motief afgekom wat nog nie ondersoek is as potensiële asimmetriese ligande nie, die 4- hidroksiebensoksasole. In hierdie tesis is gepoog om die sintese, funksionalisering en koördinasie chemie van hierdie klas verbindings te ondersoek en uiteindelik 'n metode te ontwikkel om die sintese van chirale 4-hidroksiebensoksasole vanaf aminosure te bewerkstellig. 'n Klein biblioteek van achirale 4-hidroksiebensoksasole was gesintetiseer in goeie opbrengste. Hierdie verbindings was toe behandel met verskeie oorgangsmetale, waarvan slegs die Pdsoute enige bruikbare verbindings gevorm het. Die eerste strukturele bewyse van die binding van die 4-hidroksiebensoksasole is aangeteken met behulp van enkelkristal X-straaldiffraksie ontleding van die koördinasieverbindings wat gevorm is. Verskillende koördinasie mode is aangeteken, afhangende van die ligand en die Pd-sout wat gebruik was. Die PdCl2 verbindings is ook vir katalitiese aktiwiteit met 'n Heck reaksie getoets. Die reaksie het baie goeie omskakeling gewys vir die reaksie tussen iodobenseen en stireen na stilbeen. Verdere ondersoeke het getoon dat die ligande nie ‘n beduidende rol in die reaksie speel nie en die produkte moontlik slegs as gevolg van die PdCl2 se reaktiwiteit is. Gedurende hierdie tydperk was daar ook probeer om die fenol groep met P(III) groepe te funksionaliseer. Met die uitgangstowwe sou die koördinering en katalitiese studies herhaal word. Pogings om hierdie verbindings te sintetiseer was nie suksesvol nie, met oksidasie van die P(III) na P(V) groepe of afbreking van hierdie verbindings. Pogings om dit te sintetiseer via fosfor beskermingstegnieke, deur gebruik te maak van BH3 of die in situ vasvang van die verbindings met oorgangsmetale, was ook nie suksesvol nie. Gedurende die vasvang eksperimente het die fosfien en PdCl2 ‘n herrangskikkings-produk gevorm wat op sy eie ‘n bekende en nuttige katalisator is. Ten slotte was 'n klein biblioteek van chirale bensoksasole en 4-hidroksiebensoksasole gesintetiseer, vanaf aminosure. Om die ringsluiting te bewerkstellig was ‘n Mitsunobu reaksie gebruik. Antimikrobiese toetse met hierdie verbindings het nie enige noemenswaardige resultate opgelewer nie.
2
Park, Joonwon. "Synthesis and molecular control of star-like poly-2,4-benzoxazole." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/8656.
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Avant, Lavern Marshall. "Synthesis and characterization of a cross-digitated poly (2,5-Benzoxazole) (ABPBO)." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/8464.
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Bi, Xiaoman bi. "Synthesis and Characterization of Novel Fluorescent Sensors Based on Terpyridine, Benzoxazole and Benzothiazole Chromophores." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1512743963248758.
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Njaria, Paul Magutu. "Antimycobacterial 2-aminoquinazolinones and benzoxazole-based oximes: synthesis, biological evaluation, physicochemical profiling and supramolecular derivatization." Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/26954.
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Tuberculosis (TB) is a life-threatening infectious disease caused by Mycobacterium tuberculosis (Mtb). Globally, TB is a major public health burden with an estimated 10.4 million new cases and 1.8 million deaths reported in 2015. Although TB is curable, the treatment options currently available are beset by numerous shortcomings such as lengthy and complex treatment regimens, drug-drug interactions, drug toxicities, as well as emergence of widespread multi-drug resistance. Therefore, there is an urgent and compelling need to develop new, more effective, safer drugs with novel mechanisms of action, and which are capable of shortening treatment duration. This study focused on hit-to-lead optimization of two new classes of compounds with potential anti-TB properties: 2-aminoquinazolinones (AQZs) and benzoxazole-based oximes (BZOs). A hit compound for each of these classes with low micromolar antimycobacterial activity had previously been identified through phenotypic whole-cell in vitro screening.
6
de, Souza Lucio R. "SYNTHESIS AND APPLICATION OFHIGH PERFORMANCE BENZOXAZINE-EPOXY COPOLYMERS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1618528984888642.
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7
Hutson, Leslie K. "Synthesis of Benzoxazoles Containing Allyl Crosslinking Sites via Claisen Rearrangements." Wright State University / OhioLINK, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=wright974400715.
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8
Demachy, Charles. "Synthèse électrochimique de nouveaux dérivés de la benzoxazine." Paris 5, 1995. http://www.theses.fr/1995PA05P068.
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9
Pham, Hong-Ngoc. "Synthesis of enantiopure 3,4-dihydro-2H-1,4-benzoxazine analogues for potential biological applications." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0186.
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Ce travail décrit la synthèse et l'analyse conformationnelle de pseudodipeptides et pseudotripeptides à base d’un motif 1,4-benzoxazinique énantiopur. Les énantiomères du 2,3-dibromopropionate d'éthyle et du 3,4-dihydro-2H-1,4-benzoxazine-2-carboxylate d'éthyle sont obtenus par deux stratégies (i) synthèse énantiosélective et (ii) énantioséparation des racemiques par HPLC préparative à l’échelle du multigramme. En raison de processus de racémisation au cours des synthèses énantiosélectives, l'énantioséparation des racemiques par HPLC préparative est realisée avec succès pour accéder aux différents énantiomères avec une pureté énantiomérique élevée (ee ≥ 99,5%). Les deux énantiomères du composé 1,4-benzoxazine sont utilisés pour concevoir de nouveaux pseudopeptides à base d’un motif 1,4-benzoxazinique via des réactions de couplage peptidique au niveau des extrémités C- et N-terminales. Leur préférence conformationnelle en solution et à l'état solide sont étudiées par analyses spectroscopiques (IR, RMN) et diffraction des rayons X. Les résultats indiquent (i) la prédominance d’un pseudocycle C5 impliquant un doublet non liant de l’oxygène du cycle 1,4-benzoxazinique avec un groupement NH au niveau de l'élongation de l'extrémité C-terminale et (ii) une légère influence de la configuration absolue en position C2 sur le motif 1,4-benzoxazinique et des chaînes latérales des acides aminésThis work describes the syntheis and conformational analysis of enantiopure 1,4-benzoxazine-based pseudodipeptides and pseudotripeptides. Enantiomers of ethyl 2,3-dibromopropionate and ethyl 3,4-dihydro-2H-1,4-benzoxazine-2-carboxylate are obtained by two strategies (i) via enantioselective synthesis and (ii) via preparative HPLC enantioseparation of racemate on multigram scale. Because of the racemization process during the enantioselective synthesis, preparative HPLC enantioseparation on racemates are successfully applied to afford enantiomers with high enantiomeric purities (ee ≥ 99.5%). Both enantiomers of the 1,4-benzoxazine compound are used to design new 1,4-benzoxazine-based pseudopeptides via peptide coupling reactions on C- and N-terminal extremities. Their conformational behaviour in solution and solid states are investigated by spectroscopic (IR, NMR) and X-Ray diffraction analyses. The results indicate (i) a predominant C5 pseudocycle involving a lone pair of electrons of oxygen in 1,4-benzoxazine ring with NH group from C-extremity elongation and (ii) a slight influence of the absolute configuration at C2 position of 1,4-benzoxazine scaffold and the side chains of amino acids
10
Liu, Jingping. "Synthesis, characterization, reaction mechanism and kinetics of 3,4-dihydro-2H-1,3-benzoxazine and its polymer." Case Western Reserve University School of Graduate Studies / OhioLINK, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=case1062775094.
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Schulz, Knut. "Beitrag zur Synthese und Chemie von 2H-Benzo(1,4)chalkogenazinen Darstellung neuer Lactamstrukturen, Tetrazole und Aminoketone." Berlin mbv, 2008. http://d-nb.info/992998670/04.
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Liu, Jiacheng. "Fabrication, Synthesis, and Characterization of Flame Retardant and Thermally Stable Materials: Flame Retardant Coating for Polyurethane Foam and Fused-ring Benzo-/naphthoxazines." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1491229961956675.
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Mitchell, Amy L. "Materials by design : development of poly(bis-benzoxazine)s with improved toughness properties : synthesis, analysis and molecular modelling." Thesis, University of Surrey, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435279.
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Mayer, Stanislas. "Derives de la 3,4-dihydro-2h-1,4-benzoxazine a activite antagoniste aux recepteurs gp iib/iiia synthese de 2,3,4,x-tetrahydro1,4oxazinoyindoles." Orléans, 2000. http://www.theses.fr/2000ORLE2015.
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Les derives de la 3,4-dihydro-2h-1,4benzoxazine substitues en 2 par un groupement ester sont peu etudies ; pourtant, ils peuvent constituer une ossature de choix dans l'elaboration de nouveaux composes a activite pharmacologique, par exemple, comme antagoniste aux glycoproteines gp iib/iiia. Dans le but de fonctionnaliser le noyau aromatique des 3,4-dihydro-1,4-benzoxazines, nous avons etudie leur formylation. Les composes 4-acethyle, sous les conditions de rieche, generent majoritairement des derives formyles sur le sommet 6, alors que les composes 4-benzyles conduisent exclusivement a des formylations en position 7 selon les conditions de vielsmeier-haack. La position des groupements formyles a ete validee par des authentiques elabores a partir de produits commerciaux. Ces aldehydes permettent de generer un noyau pyrrolique via une reaction d'hemetsberger. Ces composes combinent un noyau dihydro1,4benzoxazinique avec un indole ; ce sont des 2,3,4,6-tetrahydro1,4oxazino2,3-findoles (serie lineaire) ou des 2,3,4,9-tetrahydro1,4oxazino3,2-gindoles (serie coudee). Nous avons etudie la reactivite de ces substrats. L'ester de la partie dihydro1,4benzoxazine peut etre saponifie sans modifier l'ester fixe au noyau indolique. Une formylation, en serie lineaire, selon les conditions de vielsmeier-haack, conduit au substrat formyle sur le sommet 5, alors que la methode de rieche genere un compose fonctionnalise sur le sommet 8. Afin d'accroitre le potentiel therapeutique de ces nouveaux systemes tricycliques, notamment comme antitumoral, nous avons introduit un cycle supplementaire. Ceci nous a permis d'elaborer des dihydroquinolones ou des beta-carbolines jouxtant le motif 1,4oxazine. Ces substrats, apres un habillage judicieux, nous semblent porteurs d'un grand potentiel pharmacologique.
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Luo, Guo-Wei, and 羅國瑋. "Synthesis and Properties of Poly(benzoxazole-imide)Copolymer/Clay Nanocomposites." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/76168487506357286813.
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碩士國立成功大學
材料科學及工程學系碩博士班
92
Poly(benzoxazole-imide) (PBO-PI) copolymer/clay nanocomposites have been prepared from a PBO-PI precursor－poly(hydroxyamide-amic acid) (PHA-PAA) and two different organoclays. The PBO-PI precursor was made by a polycondensation reaction between 2,2-bis(3-amino-4-hydroxyphenol) hexafluoropropane (BisAPAF), 4,4-oxydiphthalic anhydride (ODPA) and isophthaloyl dichloride (IC). The organoclays were formed by a cation exchange reaction between a Na+-montmorillonite clay and an ammonium salt of dodecylamine (DOA) or 4-phenoxyaniline (POA). The glass transition temperature (Tg) of PBO-PI copolymer is 331℃. Both X-ray diffraction (XRD) and transmission electron microscope (TEM) analyses showed that the organoclays were dispersed in PBO-PI copolymer matrix in a nanoscale. The in-plane coefficient of thermal expansion (CTE) of PBO-PI copolymer/clay film was decreased with the increasing amount of organoclay. The CTE of PBO-PI copolymer/clay film which contained 7 wt % DOA-clay was decreased 35% compared to the pure PBO-PI film and the CTE of PBO-PI copolymer/clay film which contained 7 wt % POA-clay was decreased 33%. The thermal decomposition temperatures of PBO-PI copolymer/clay films increased with the increasing amount of organoclay. The tensile modulus of PBO-PI copolymer/clay films increased with the increasing amount of organoclay. The tensile modulus of PBO-PI copolymer/clay film which contained 7 wt % DOA-clay was increased 95% compared to the pure PBO-PI copolymer film and the tensile modulus of PBO-PI copolymer/clay film which contained 7 wt % POA-clay was increased 68%. The water absorption of PBO-PI copolymer/clay film was decreased with the increasing amount of organoclay. From UV-Vis spectra, the PBO-PI copolymer/POA-clay film showed a better transparency than the PBO-PI copolymer/DOA-clay film. That could be due to the fact that POA has a higher thermal stability than DOA.
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Chang, Ying-Ching, and 張孆璟. "Synthesis of Anticacer Bis (benzimidazoles) Library and Benzimidazolyl benzoxazole Related to UK-1." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/8s3bfm.
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Chen, Tai-an, and 陳泰安. "Synthesis and Characterization of New Polyimides Containing Pendent Benzimidazoles Groups and Polybenzimidazoles Containing Pendent Benzoxazole Groups." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/93346838677936173720.
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碩士國立臺灣科技大學
化學工程系
102
Part 1 A series of new polyimides (PIs) with pendant benzimidazole had been synthesized. They had inherent viscosities in the range of 0.96~1.20 dLg-1, and they could form tough and flexible films. The PIs exhibited high thermal stability with 10% decomposition temperature more than 500℃ in nitrogen, and their and soft temperature around 300℃. These films exhibited good mechanical properties with tensile stress exceeded 132 MPa.However,the mechanical properties of phosphoric acid doped PI significantly decreased. The mechanical properties of crosslinked polyimides (C-PI) were improved via crosslinking reaction of methyl group. The proton conductivity of phosphoric acid doped PBI was dependent on doping PA level and temperatures. The proton conductivity of BPBI8mBI1F0.5DMB0.5 and C5-BPBI8mBI1F0.5DMB0.5 were 75.4 and 78.4 mS/cm at 160℃,respectively.The proton conductivity of PI and C-PI were significantly higher than m-PBI (52.0 mS/cm).Thus, these polyimides (PIs) with pendant benzimidazole membranes could be the promising materials alternative to m-PBI membrane for medium-temperature fuel cells applications because they had high proton conductivity,and good thermal stability. Part 2 A series of new polybenzimidazoles (PBIs) with pendant benzoxazole had been synthesized. They had inherent viscosities in the range of 0.85~2.4 dLg-1, and they could form tough and flexible films. , The PBIs exhibited high thermal stability with 10% decomposition temperature more than 470 ℃ in nitrogen, and their glass transition temperature and soft temperature around 300℃. These films also exhibited good mechanical properties with tensile stress exceeded 70 MPa. However, the mechanical properties of phosphoric acid doped PBI significantly decreased. This is the study that improved mechanical properties of proton exchange membranes via crosslinking reaction of methyl groups.The tensile strength of cross-linked PBI was a approximately twice as strong as uncross-linked PBI. The proton conductivity of phosphoric acid doped PBI was dependent on doping PA level and temperatures. The proton conductivity of PBI-3-3 was 60.2 mS/cm at 160 ℃.The proton conductivity of PBI-3-3 was higher than m-PBI (52.0 S/cm). The proton conductivity of C-PBI-3-3 was 51.7 mS/cm at 160℃,the tensile strength of crosslinked C-PBI-3-3 was about double.Thus, these polybenzimidazoles (PBIs) with pendant benzoxazole membranes could be the promising materials alternative to m-PBI membrane for medium-temperature fuel cells applications because they had high proton conductivity,and good thermal stability.
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Chen, Szu-Yuan, and 陳思源. "Synthesis and Characterization of New Polybenzimidazoles Containing Pendent Benzoxazole Groups for Proton Exchange Membrane Fuel Cell at Intermediate Temperature." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/19376040315169121072.
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碩士國立臺灣科技大學
化學工程系
101
A series of new polybenzimidazoles (PBIs) with pendant heterocyclic ring have been synthesized. The resulting polymers showed good solubility in aprotic solvents. They had inherent viscosities in the range of 0.92~1.9 dLg-1, and they could form tough and flexible films. They exhibited high thermal stability with initial decomposition temperature ranging from 653 to 705 in nitrogen, and their glass transition temperature around 300℃. These films exhibited good mechanical properties with tensile stress exceeded 94.5 MPa. Phosphoric acid (PA) doped PBI was swollen result in the volume of PBI showed a larger volume swelling. The mechanical properties of phosphoric acid doped PBI significantly decreased. This is the first study that improved mechanical properties of proton exchange membranes using crosslinking in methyl pendent PBIs. Mechanical strength of cross-linked PBI is twice as strong as noncross-linked PBI. The proton conductivity of phosphoric acid doped PBI was dependent on doping PA level and temperatures. The proton conductivity of PBI-1-10 was approximately 61.6 mS/cm at 200 ℃, compared with 57.8 mS/cm of m-PBI membrane. The proton conductivity of C5-PBI-1-10 was approximately 67.7 mS/cm at 200 ℃. Thus, these polybenzimidazoles (PBIs) with pendant heterocyclic ring membranes could be the promising materials alternative to Nafion membrane for medium-temperature fuel cells applications because they had high phosphoric acid doped, good thermal stability, and higher proton conductivity.
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McKee, Mireya Loreley 1978. "Synthesis and biological evaluation of 2-(2'-hydroxyphenyl) benzoxazole analogs of UK-1 and G-quadruplex selectivity of perylene diimide compounds: /." Thesis, 2007. http://hdl.handle.net/2152/3634.
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A great number of pharmaceutical drugs target nucleic acids. However, drug-DNA interactions can be region non-specific and lead to undesired side effects. Understanding the mechanisms that regulate drug-DNA binding can help in the design of potent and selective therapeutic agents with fewer deleterious side effects. The present investigation explores the metal-mediated DNA binding of a group of 2-(2-hydroxyphenyl)benzoxazole (HPB) ligands and the aggregation dependant G-quadruplex selectivity of a series of perylene tetracarboxylic acid diimides (PTCDI) compounds. HPB ligands are simplified analogs of the bis-benzoxazole natural product UK-1. This compound is able to inhibit cell growth of various tumor cell lines, bind divalent cations, and interact with DNA in a metal dependant fashion. The HPB moiety present in UK-1 was identified as relevant for its metal ion binding and biological properties. For this work, novel HPB ligands were synthesized with different substitutions at the C4 or C7 position. Their ability to bind metal ions and DNA was evaluated and their cytotoxicity was assessed in multiple cancer cell lines. The ligands bound to Cu²⁺ with the highest affinity among metals studied. Consequently, Cu²⁺ promoted the most dramatic increase in DNA binding and affected the ligand's cellular cytotoxicity. The second project focused on targeting four-stranded structures called G-quadruplexes, which can form in G-rich nucleic acid sequences. Compounds that stabilize these structures may inhibit nucleic acid-processing enzymes such as telomerase and potentially act as anti-cancer agents. PIPER is a PTCDI that is particularly selective for G-quadruplex DNA versus duplex DNA under conditions in which it forms aggregates. This work investigated ligand aggregation in a series of PIPER analogs with different structural features under high and low salt buffers, changes in pH, metal binding and temperature changes. A negatively charged analog was determined to form metal-mediated aggregates while novel thermophilic mediated aggregation was discovered for an analog with methoxyethoxymethyl groups. The ability of these ligands to bind different DNA structures was evaluated under aggregating and non-aggregating conditions. This study supports the idea that ligand aggregation increases their quadruplex selectivity and decreases double-stranded DNA binding.
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Chou, Yu Wei, and 周裕偉. "Synthesis and properties of dicyclopentadiene-basedcyanate ester/benzoxazine and phosphinated cyanateester/benzoxazine copolymers." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/92400815954383040094.
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碩士國立中興大學
化學工程學系所
103
Dicyclepentadiene-phenol (DP) has rigid aliphatic structure, commonly used in enhancing thermal property and dielectric property for materials. In the study, DP was modified into cyanate ester, DPCY, and blended with bifunctional benzoxazine, 4,4’-diaminodiphenyl ether-based benzoxazine(ODABz). The two resins co-reacted when being cured. The dielectric constants were decreased by adding DPCY in to the thermosets. The resulting materials achieved great thermal properties, thermal stability, and dielectric properties. The hydrophobicity of the materials was also decreased because of the aliphatic structures. In the development of materials with flame-retardancy, DOPO has outstanding flame-retardancy, and increases thermal stability and hydrophobicity because of the rigid aromatic structures. The novel tetrafunctional phenolic monomers were synthesized by reacting with DOPO and further modified into cyanate esters. Blended with ODABz, the thermosets have great thermal properties, thermal stability, hydrophobicity,and flame -retardancy.
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Chien, Chun-Kai, and 簡君愷. "Synthesis and characterization of chalcone-containing benzoxazine." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/76181071001805425180.
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碩士國立中興大學
化學工程學系所
103
The photosensitive chalcone-containing benzoxazine (2) was synthesized successfully from chalcone-containing bisphenol, aniline and paraformaldehyde by one-pot procedure. The [2+2] cycloaddition of the chalcone moiety after UV irradiation was monitored by FTIR and UV-vis spectra. To investigate the effect of photodimerization on thermal and mechanical properties, two steps curing procedure was performed. After the cycloaddition of the chalcone moiety by UV-irradiation, the ring-opening polymerization of benzoxazine was performed by thermal curing. Due to the enhancement of the crosslink density, the UV-irradiated thermosets exhibit good thermal and mechanical properties.
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Chen, Zih-Jyun, and 陳姿君. "Synthesis and characteristic of photo-curable benzoxazine thermoset." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/64751732305461184362.
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碩士國立中興大學
化學工程學系所
103
A novel benzoxazine resin with photosensitive group was synthesized. Based on the photosensitive group, the cross-linking points were increased. It was cured by two procedures. First, the benzoxazine was photo-cured by UV light, followed by the thermo-curing. The structures of monomer (1) and (2), including photosensitive group, were monitored by 1H NMR, 13C NMR and FTIR analysis. The monomer (2) could produce two different kinds of structures after thermo-curing and photo-curing. The monomer (2) has the great difference in mechanical, dimensional stability, and thermal properties as well as thermal stabilities through different procedures, only thermo-curing and thermo-curing plus photo-curing.
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蔡相芸. "Synthesis and Characterizations of Benzoxazine Containing Uracil Group." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/73646505656288154528.
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碩士國立交通大學
應用化學研究所
98
Polybenzoxazine is an addition polymerized phenolic resin, having a wide range of interesting features and the capability to overcome several shortcomings of conventional novolac and resole type phenolic resins. In many literatures, we learned that the properties of polybenzoxazines can be tuned by inducing different functional groups into the molecular structure of benzoxazine. In this thesis, a new benzoxazine monomer, uracil based benzoxazine (UBZ), possessing multiple hydrogen bonding interaction sites was successfully prepared. By inducing UBZ to BZ, the self-complementary interaction within uracil would result in relatively lower ring-opening polymerization temperature. In addition, the anti -bacterial test indicated that PUBZ had the potential for biological application.
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Tzeng, Yao-Ting, and 曾耀霆. "Synthesis and Characterization for Different Side Chain Benzoxazine Nanocomposites." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/26086655139870413921.
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碩士國立高雄應用科技大學
化學工程與材料工程系
98
Polybenzoxazines have evinced significant interest as a class of high performance polymer. These novel materials gain attention because of low volumetric shrinkage upon curing, minimal moisture absorption, excellent resistance to chemicals. However, the low crosslinking densities of benzoxazine resins leaded to insufficient in mechanical properties and thermal stability. Therefore, for improve mechanical properties and thermal stability, the molecular design flexibility and added reinforcements would be employ. The goal of this research is focused on the synthesis of different side chain benzoxazines and hybrid with polyhedral oligomeric silsesquioxane(POSS) to preparation for nanocomposites. 6,6-Bis(3-phenyl-3,4dihydro-2H-1,3-benzoxazinyl) isopropane (Bz-A), 6,6-bis(3-phenyl-3,4dihydro-2H-1,3-benzoxazinyl) methylene (Bz-F) and 6,6-bis(3-phenyl-3,4dihydro-2H-1,3-benzoxazinyl) ethylbenzene (Bz-ap) can be use the bisphenols which contain different pendant group with aniline and paraformaldehyde through solventless method to synthesis. The structure of synthesized Benzoxazines will be confirmed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), and their thermal curing behavior of Benzoxazines was studied by differential scanning calorimetry (DSC). The properties of cured Benzoxazines were studied by dynamic mechanical analysis (DMA), thermal gravimetric analysis (TGA). The results show that Benzoxazines at curing process have high autocatalytic effect. In mechanical and thermal stability properties, Bz-F had excellent properties than Bz-A and Bz-ap, because of higher cross-linkes and it was attributed to lower steric hinderance. Various contents of POSS were added into Bz-A, Bz-F and Bz-ap, respectively. The thermal curing behaviors of thermocurable nanpcomposites were investigated, and their cured network’s physical properties were also investigated. The results indicate that the autocatalytic effect of Benzoxazines would be decrease after added POSS. The mechanical and thermal stability properties of nanocomposites were increased with the increasing of POSS contents, whereas when POSS contents over 5wt%, the properties slightly decreased.
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AlfredMurni and 穆米. "Benzoxazine Containing Triphenylamine Moiety: Synthesis, Characterization and Electrochemical Properties." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/48404065445015707713.
Full textAbstract:
碩士國立成功大學
化學工程學系碩博士班
98
A novel benzoxazine containing triphenylamine moiety: 3-triphenylamine-3,4-dihydro-2H-1,3-benzoxazine (TPA-Ba) have been synthesized from 2-hydroxybenzaldehyde, 4-aminotriphenylamine and paraformaldehyde. The monomer was characterized by 1H NMR, Elemental Analysis (EA) and Fourier Transform Infrared (FTIR). DSC analysis of the monomer shows two peaks, one is an endothermic peak at 144 °C which corresponds to the melting point of the monomer and an exothermal peak at 240 °C which corresponds to the ring opening process of the benzoxazine ring. The monomer underwent thermal polymerization in order to form polybenzoxazine (PTPA-Ba). The obtained polybenzoxazine have molecular weights of 8347, as measured by GPC. The polymer was characterized by FTIR and 1H NMR. The polymer shows good solubility in common organic solvent and good thermal stability. The ring opening polymerization of benzoxazine ring was investigated and found to be following mechanism B, which resulting the phenolic type polybenzoxazine. Electrochemical study was performed on PTPA-Ba. Electrochemical study of PTPA-Ba shows that electropolymerization can occur on PTPA-Ba. As a result of electropolymerization, thin film will be formed on top of ITO glass surface. The HOMO and LUMO energy levels of PTPA-Ba was measured in order to investigate the potential of PTPA-Ba as hole transporting material.
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Lin, Yu-Hsiang, and 林鈺翔. "Synthesis and Characterization of Adamantane-Containing Polyimiede and Benzoxazine." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/18281789193094479727.
Full textAbstract:
碩士國立中興大學
化學工程學系所
104
The research is divided into two parts. The first part is synthesis of adamantine-containing polyimide. (2) will be prepared by the nucleophilic aromatic substitution reaction of (1) and 1-chloro-4-nitrobenzene. Novel diamine (3) with adamantly group will also be prepared by the reduction of (2) in the presence of hydrogen and Pd/C as catalyst. The polyimides were polymerization from (3) and series dianhydride such us PMDA, ODPA, BTDA, BPADA。Novel polyimides exhibit superior thermal properties, thermal stability, low dielectric and low water absorption. In the second part, Adamantan-containing benzoxazine with OH group were prepared from the concept of steric hindrance from diol (1), in which the OH group ortho to adamantly group, the hindered OH, is not reactive toward aldehyde. The structures of the monomers were confirmed by 1H NMR, 13C-NMR, FTIR spectra. Copolymers were prepared co-curing BADCY and (2) with various molar ratio (1 %, 2 %, 5 %, 10%, 30% based on BADCY). For copolymers, the imidocarbonate linkeages, resulting from the reaction of phenolic OH and high polar OCN group, were able to reduce dielectric constant.
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Guang-YuChen and 陳光宇. "Acetylene-Containing Benzoxazine: Synthesis, Curing and Thermal Properties of Cured Product." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/55779434588195221638.
Full textAbstract:
碩士國立成功大學
化學工程學系碩博士班
100
In order to develop a strong toughness also have high thermal stability materials with high toughness benzoxazine groups connected to the acetylene functional groups with high thermal stability. We successfully have used two methods to get the acetylene-cantaining benzoxazine. In one way we use solvent less method, but only get the yield 27 ％, and the other way not only improve the yield to 60 ％, but also identify inter-medium very clearly by NMR, IR, and EA. Then we have some research on acetylene-cantaining polybenzoxazine curing condition. In order to find what the situation we can get the best cross-linking density. And used the TGA, we can get the temperature of weight loss 5 ％ and 10 ％, moreover char yield at 800 ℃. Trough different thermal curing conditions, we have found curing in solvent can raise char yield to 68 ％, and temperature of weight loss 10 ％ was 530℃, it was the best conditions. In order to test Mechanical properties, we use the tensile machine, to the measured stress-strain curve. We found that toughness property is better than curing polymer such as PAA, and the strength of the material was 691 MPa. In this study we find that our products have excellent thermal property and mechanical properties, indicating that it might replace phenolic resins.
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Tian, Yu-Wei, and 田諭瑋. "Synthesis of Fluorene-based Benzoxazine and Phosphinated Multifunctional Epoxy Curing Agents." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/yn58d4.
Full textAbstract:
碩士國立中興大學
化學工程學系所
99
Part I： We successfully synthesized fluorene-containing benzoxazine compound (2) by a facile, widely useful three-step method. Compound (2)’ was synthesized by a co-solvent method. Their chemical structures were confirmed by FT-IR and 1NMR analysis. In the PL analysis, the compound (2) exhibits a blue emission at about 395nm as well as emission band between 350nm〜450nm. The curing behaviors of the precursor were monitored by differential scanning calorimetor(DSC) and its crosslink polymer has a high refractive index. The compound (2) served as curing agents for diglycidyl ether of bisphenol A (DGEBA) and cresol novolac epoxy (CNE). As the result, P-2/CNE dispalys higher Tg than P-2/DGEBA. All series have a 5% weight loss over than 400℃,and the char yield at 800 oC in nitrogen range from 31% to 53% respectively. Therefore, fluorene-incorporation is an effective approach to endow many attractive properties to polymers in one attempt. Part II： It has been reported that the secondary carbocation then arranges into a more stable tertiary carbocation. A nucleophilic addition occurs at the tertiary carbocation easily. Based on our knowledge in conjugate addition, we used very cheap industrial material. According to the fragmentation chemistry of bisphenol A and our knowledge in conjugate addition chemistry of DOPO. We reacted to the bisphenol A and DOPO in the catalysis p-toluenesulfonic acid, and the compound (1) was successfully prepared. Based on the successful reaction, we prepared the phosphinated curing agents via a one-pot reaction of Bisphenol-A novolac and DOPO in the catalysis p-toluenesulfonic acid. In order to enhance the molecular weight and Tg, we used the mild conditions. The resulting epoxy thermosets show the excellent flame retardancy.
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Xiong, Tsai Sheng, and 蔡勝雄. "Syntheses and Properties of Novel Epoxy Curing Agents and Benzoxazine." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/63706784670943641280.
Full textAbstract:
碩士國立中興大學
化學工程學系
93
A novel phosphorus-containing tri-functional novolac (dopotriol) was synthesized from the addition reaction of 9,10-dihydro-9-oxa-10-phosphaphenan threne 10-oxide (dopo) and rosolic acid. The structure of dopotriol was confirmed by NMR spectrum and elemental analyses. The dopotriol was blended with phenol novolac (PN) in the ratio of 10/0, 8/2, 6/4, 4/6, 2/8 and 0/10 to serve as curing agents for diglycidyl ether of bisphenol A (dgeba). Thermal properties such as Tg, thermal decomposition temperature, flame retardancy, moisture absorption and dielectric properties of cured epoxy resins were evaluated. The activity and activation energy of curing were studied using the methods of the Kissinger and Ozawa by dynamic DSC scans. The glass transition temperatures of cured epoxy resins are in the range of 138-159 oC, increasing with the phosphorus content. This is rarely seen in the literature after introducing a flame retardant element. The flame retardancy increases with phosphorus content and a UL-94 V-0 grade can be achieved with phosphorus content of 1.87%. Similar dielectric properties and moisture absorption were observed for these phosphorus-containing epoxy resins, implying that the introduction of phosphorus into epoxy does not affect the dielectric properties and moisture absorption. We also synthesized another novel phosphorus-containing triamine (dopo-ta) from the nucleophilic addition of 9, 10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (dopo) and pararoaniline chloride using triethylamine as a catalyst. We confirmed the structure of dopo-ta by IR, Mass, NMR spectrum and elemental analysis. The dopo-ta was served as a curing agent for diglycidyl ether of bisphenol A (dgeba) and dicyclopentadiene epoxy (hp7200). Properties such as glass transition temperature, thermal decomposition temperature, flame retardancy, moisture absorption and dielectric properties of cured epoxy resins were evaluated. The glass transition temperatures of cured dgeba/dopo-ta and hp7200/dopo-ta are 171 oC and 190oC, respectively. The flame retardancy increases with the phosphorus content and a UL-94 V-0 grade can be achieved with a phosphorus content of 1.80 wt % for dgeba/dopo-ta/ddm and 1.46 wt % for hp7200/dopo-ta/ddm systems. The dielectric constant for dgeba/dopo-ta and hp7200/dopo-ta is 3.00 and 2.89, respectively, implying dopo-ta curing system exhibits low dielectric properties. A trifunctional benzoxazine, dopot-m and CH3t-m, was prepared from dopotriol and 1,1,1-Tris(4-hydroxyphenyl)ethane, and their structure were confirmed by NMR and IR spectra, etc. The synthesized benzoxazines were blended with another benzoxazine based on 4,4’-dihydroxydiphenylmethane (F-a) in the different ratios. Glass transition and thermal degradation behaviors of these thermosets were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The materials exhibited high glass transition temperatures and thermal decomposition temperature. V-0 materials were obtained when dopot-m/F-a were tested for ignition resistance with the UL-94 test.
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Chung, Yun-Cheng, and 鍾昀澄. "Novel benzoxazine-based diols as chain extender for polyurethanes: synthesis and characterization." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/6kmmm7.
Full textAbstract:
碩士國立臺灣大學
高分子科學與工程學研究所
107
A series of poly(benzoxazine-co-urethane)s with novel benzoxazine diols as chain extenders were successfully developed in this work. These diol chain extenders were obtained by differents bisphenol (Bisphenol A, Bisphenol F, CPDP) compounds refluxed with 6-amino-1-hexanol and paraformaldehyde. The soft segments of PU were chosed form polytetramethyleneetherglycol (PTMEG), polycaprolactone (PCL), polycarbonate diol (PCPO) and the diisocyanate of the PU was 4,4-methylenediphenyl diisocyanate (MDI). poly(benzoxazine-co-urethane)s were synthesized by a two-step polymerization method, in which the diisocyanate reacted with polyols first and then reacted with the chain extenders. The characterization of benzoxazine diol monomers were performed by 1H-NMR. The PU films were characterized by FTIR. The curing temperature of poly(benzoxazine-co-urethane)s are detected by DSC scans, the result exhibited two exothermic peaks in a range of 160-250 oC. Four possible mechanisms were used to explain the phenomena of lower curing temperature. They are including: (1). Benzoxazine attacked by residual isocynated group, (2). By residual primary amine, (3). Hydroxyl group on chain extender, and (4). Intrinsic of benzoxazine core attack urethane linkage. For the sake of decomposition issue, the curing temperature was set at 150 oC. In this research of PU formula, PCPO-MDI-CPDPBBD45 uncured and cured samples exhibited the best performance in tensile stress and DMA measurement. They are 9.1 MPa ( elongation is 141 %) in stress-stain plot and DMA exhibited the loss modulus temperature at 150 oC. The TGA test the thermal stabilities of poly(benzoxazine-co-urethane)s and the results showed polyurethanes with higher benzoxazine content and cardo structure show higher char yield at high temperature, which suggested they possessed better thermal stability. In stress-strain curves, with more rigid backbone, the cardo-type polyurethanes possessed better mechanical properties than those polyurethanes based on BPABBD and BPFBBD. The mechanical properties can be modified with different composition of benzoxazine. The trend suggested PU-Bzs possess the potential for the application needed for high mechanical reinforcement.
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Chen, Guan-Ming, and 陳冠明. "Study on Epoxy-Benzoxazine group for Maleimide Resins,Synthesis,properties and structure." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/54937697860717446440.
Full textAbstract:
碩士國立高雄應用科技大學
化學工程系碩士班
95
In this study, two kinds of Epoxy-Maleimide Monomer (EMM) and Benzoxazine-Maleimide monomer (BMM) were synthesized from N-(4-hydroxyphenyl)maleimide (HPM ). The monomer EMM or BMM was cured with DOPO at various content, and their curing behaviors investigated by differential scanning calorimetry (DSC). The properties of the resins were studied by Dynamic viscoelastic analysis (DMA), Thermogravimetric analyzer (TGA), Dielectric analyzer (DEA) and UL-94V test. The kinetic parameters were studied by dynamic DSC. According to the results, the most main factors to influence reaction are electric transform and steric hindrance. The physical poperties measurement, although introduced DOPO into EMM and BMM which reduced the crosslinking density of these resins and Tg of the cured resins decreased as the DOPO content increased, however the co-reactant resins exhibited better themal stability and lower dielectric constant. In UL-94V test, indicated that because of the synergistic effect, the UL-94 V-0 rating can be achieved with phosphorus content of as low as 5~15 phr.
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Wang, Meng-Wei, and 汪孟緯. "Benzoxazine: Synthetic Modification, Mechanism, and Microstructure of Its Resulting Thermoset." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/32363084905175506322.
Full textAbstract:
博士國立臺灣大學
高分子科學與工程學研究所
104
A main chain-type polybenzoxazine precursor, P(BF-bapp)-1, with high molecular weight (MW) was prepared through a strategy of A-A and B-B polycondensation, avoiding by-reaction that occurred in Mannich condensation. To discuss the effect of the MW of benzoxazine on the properties and microstructure of the resulting thermoset, anthother three structurally similar benzoxazines with difference MW were syntheized in this work. To discuss the mechanism of ring-opening polymerization (ROP) of benzoxazine, three polybenzoxazine precursors were prepared. Among the polybenzoxazine precursors, free ortho positions to the O and N of oxazine are available for PBz-0M. The ortho positions to the O of oxazine are blocked by methyl group for PBz-2M. The ortho positions to the O and N of oxazine are blocked by methyl group for PBz-6M. According to DSC, IR, and thermal analysis, we found that the ROP of PBz-2M can be carried out through free ortho positions to the N of oxazine. A reaction mechanism was proposed to explain the polymerization in this work. Blends of cyanate ester and benzoxazine have been independently studied by several researchers, some of them suggest that the rapid trimerization of cyanate ester in the blend is related to the ring-opened structure of benzoxazine. Recently, we unexpectedly observe that gelation occurred in solution of P-oda/BACY blend after 24 h at room temperature. However, the possibility of ring-opening polymerization for benzoxazine at room temperature is rare. Therefore, it is highly likely that the catalytic effect results from the benzoxazine itself. We tried to find the reason of gelation through model reaction in this work, and proposed a catalytic mechanism of benzoxazine for the trimerization of cyanate ester.
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Lin, Laing-Kai, and 林莨凱. "Synthesis, characterization and properties of silicon- or phosphorous- containing benzoxazine monomers and polymers." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/20700451156473593654.
Full textAbstract:
碩士中原大學
化學工程研究所
100
In this study, the development of novel methods to synthesize monomers with benzoxazine functional groups is investigeated to overcome the disadvantage of benzoxazine by designing the molecular structure, physical, and chemical properties. The first part is to use silicon-containing poly (dimethylsiloxane - co - methylhydrosiloxane), trimethylsilyl terminated (Si-H (13000)), and phosphorus diethylphosphite (DEP), 2 - [(phenylimino) methyl] phenol (PIMP), and paraformaldhye for synthesis of monomers containing silicon or phosphorus. The samples were charaterized using Fourier transform infrared spectroscopy (FT-IR), hydrogen silicon and phosphorus spectra NMR (1H, 29Si, 31P - NMR), elemental analysis (EA), to confirm the monomer chemical structure to prove the successful synthesis of these two monomers. Then by the discussion in two parts, first part is a long-chain benzoxazine monomers containing silicon, the main chain of this monomer is silicon oxide so it has a softness and fire resistance with a benzoxazine functional groups has carries on ability of the polymerization which also can use as a modifier, then post in the mold to heat up till carry on the ring-opening reaction, this method is called “curing”. After complete polymerization, the poly (Si-H (13000)-Bz,) has the high Td5% at 332 oC and has a good spare, the mapping diagram can be found in the EDX detection dispersion is quite good. After prepares the blocks by the curing method in different weight ratio, expected that the softness and fire-resistance can increase the thermal stability of the bulk and the crispness. Experimental results show that when the BPA-FBz mixing 5wt% into Si-H(13000)-Bz, the thermal stability and LOI are improved, even if added to a 20wt%, the compatibility is also quite good. At last, all the LOI values are achieve the fire resistance standards. In Addition, the toughness of these samples has improved, when poly(Si-H(13000)-Bz) mixing 7wt% into BPA-FBz, the strain up to 8.6 percent, more than twice the original. The second part, for the phosphorus-containing monomers, with P = O groups can enhance fire resistance and also contains a benzoxazine functional groups can be polymerization to promote its physical properties, then in the DSC, can see a melting point at 70 oC and the exthermic peak at 210 oC is for ring-opneing reaction, while the DSC figure can see a wide processing range from the melting point to the ring-opening reaction point, also has excellent solubility can be soluble in common industrial solvent. After the same in a different weight ratio blend with the general benzoxazine, wish the phosphorus element can increase the fire resistance of the copolymer. The experimental results showed that its char yield and LOI values increase with the increase of the DEP-Bz content, and all the LOI value are achieve the fire standards, In addition, after the DMA detection, mixing 20wt% show the high value of glass transition temperature is 248 oC. With these result can say that mixing with DEP-Bz can increas the thermal stability and char yield, in LOI values are achieve the fire resistance standard, also can use as a modifier to add different materials which have a broad range of applications.
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Chen, Nan-Shiun, and 陳南勳. "Synthesis and Characterization of Benzoxazine-Containing Sulfonated Polyelectrolytes for Direct Methonal Fuel Cell." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/86402537351847952475.
Full textAbstract:
碩士中原大學
化學工程研究所
100
Abstract The purpose of this study is to develop a polymer material containing sulfonic acid functional groups, which are further used as polyelectrolyte membrane in direct methanol fuel cells. A novel new monomer BAPBDS-BMI containing sulfonic acid and bismaleimide groups was synthesized from 4,4’-bis(4-aminophenoxy)biphenyl (BAPB) and characterized. This new monomer was further reacted with benzoxazine and furan containing BPA-FBz monomer via Diels-Alder reaction to prepare a linear polymer BA-DA. This newly synthesized polymer containing benzoxazine and sulfonic acid groups was hot-pressed and cured into free standing flexible thin film. The curing process induces the ring opening reaction of benzoxazine groups, resulting in crosslinking effect in the polymer. The membranes are then further applied in fuel cell. Although the degree of sulfonation of BA-DA membrane and commercialized membrane Nafion-117 is very close, but due to the crosslinking effect inside the BA-DA membrane, this membrane shows improved swelling property, dimensional stability and methanol permeability compared with Nafion-117. The proton conductivity of BA-DA membrane is 5×10-2 S/cm, which is lower than that of Nafion-117 (9.1×10-2 S/cm), but the methanol permeability is 6 times higher than that of Nafion-117, and hence the selectivity is 3 times better than Nafion-117. For this reason, we predicted that BA-DA membrane will show better performance than Nafion-117 in DMFC.
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Yu, Juin-Meng, and 游俊盟. "Synthesis and properties of benzoxazine with maleimide functional group, polybenzoxazine resin curing study." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/tc4h8q.
Full textAbstract:
碩士中原大學
化學工程研究所
93
Abstract In this study, a maleimide-containing benzoxazine monomer, 3-phenyl-3-4-dihydro-2H-6-(N-maleimido)-1,3-benzoxazine (HPM-Ba), was prepared with using N-(4-hydroxyphenyl)maleimide, formaldehyde, and aniline as starting materials. The chemical structure of HPM-Ba was confirmed by FT-IR, 1H-NMR, and Elemental Analysis measurements. A two-stage thermal polymerization was observed with HPM-Ba under heat, in which the first stage was the reaction of maleimide groups and the second one was the ring-opening reaction of benzoxazine groups. The reaction scheme was demonstrated with differential scanning calorimetry (DSC) and thermal-stage FT-IR observation. The completely cured P-HPM-Ba-Ⅱ polymer exhibited a high glass-transition temperature of 204℃, good thermal stability about 330,℃and self-extinguishing behavior . In addition, cured polymers were also obtained from the blends of 3,4-dihydro-3-phenyl-2H-1,3-benzoxazine（PPA）and various maleimide compounds. The effect of pendent groups of maleimide derivates on the polymerization scheme of the monomer blends were studied by DSC. The ring-opening polymerization of benzoxazine groups was catalyzed by the acidic –OH and –COOH groups in maleimides. The catalytic effects were directly observed with DSC measurements and the reaction scheme was confirmed with TGA-GC/MS measurements on the evolved gases in degradation. Meanwhile, the polymerization maleimide group was also catalyzed with benzoxazine groups. These catalytic effects shifted the polymerization of the monomer blends toward low temperatures. Therefore, polymers from PPA and P-cpm (maleimide with carboxylic acid group) showed the lowest polymerization temperature and the highest glass-transition temperature（224 ℃）among the cured polymers. It was concluded that combination of maleimide and benzoxazine resulted in high performance thermosets, both in processing and properties.
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Wang, Po-Jen, and 王柏仁. "Synthesis and properties of cyanate ester and benzoxazine thermoset with improved electrical conductivity." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/5nr35y.
Full textAbstract:
碩士國立中興大學
化學工程學系所
100
We have successfully prepared maleimide-functionalized CNTs (BMI-CNT) via Diels-Alder reaction of MWCNTs with 1,1''-(methylenedi-p-phenylene)bismaleimide (DDM-BMI) . Among the solvent we have tried, DMAc is the best solvents for the modification, as supported by thermal gravitational analysis of organic content. IR spectrum confirms the C=O, and C-N bonds of BMI-CNT. The modification was also supported by intensity change of ID/IG in Raman spectrum, and the well dispersion of BMI-CNT in DMSO, DMF, and ethanol. The maleimide linkage act as a bonding cite with cyanate ester. Phenolic OH-containing benzoxazine (o-OHBz), which cannot be easily prepared by traditional procedures, have successfully been prepared from the condensation of bis(4-amino-3-phenol) and 2-hydroxybenzaldehyde, reducing the resulting imine linkage by NaBH4, and ring closure condensation. The phenolic OHs can provide a reaction cite with epoxy and 1,1''-(methylenedi-p-phenylene)bismaleimide (DDM-BMI). The structure-property relationships between p-OHBz/epoxy, F-a/epoxy, p-OHBz/DDM-BMI, F-a/DDM-BMI copolymers were discussed.
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Dai, Kang-Hong, and 戴嵻宏. "synthesis of phosphorus-containing multifunctional benzoxazine and thermal properties of the resulting thermosets." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/r6p9xm.
Full textAbstract:
碩士國立中興大學
化學工程學系所
101
PART I We have successfully synthesized phosphorus-containing multifunctional benzoxazine, P-BPA-3b-BZ and P-BPA-5b-BZ by one-pot approach using toluene/ethanol (2/1) as solvent. Ring-opening polymerization types of curing systems were tracked by FTIR. The mechanical property, thermal stability, electrical property and flame retardancy of thermoset systems cured by various BZs with epoxy resins (DGEBA or CNE) were analyzed DMA, TGA, impedance analyzer and UL 94 flame rating. PART II A novel difunctional phenolic diastereomer, P-D2HB, from D2HB and DOPO, was successfully synthesized by using toluene as solvent. Catalyzed by TPP, various PD-D(1.0、1.5、2.0) with different phosphorus contents(1.0%、1.5%、2.0% )were synthesized from P-D2HB and DGEBA, and were characterized by epoxy titration method. All thermoset systems cured from PD-D with DDS demonstrated excellent properties in Tg(160℃up), CTE(58~70 ppm/oC) and flame retardancy.
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Chou, Ching-I., and 周進義. "Design and Synthesis of Novel Benzoxazine Monomers and Characterization of Their High Performance Thermosets." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/96873811888451765420.
Full textAbstract:
博士中原大學
化學工程研究所
96
Abstract In this study, five novel benzoxazine monomers (3-phenyl-3,4-di- hydro-2H-6-(N-maleimido)-1,3-benzoxazine, HPM-ABz; 3-furfuryl-3,4- dihydro-2H-1,3-benzoxazine, P-FBz; bis(3-furfuryl-3,4-dihydro-2H-1,3- benzoxazine)isopropane, BPA-FBz; 6-fluoro-3-furfuryl-3, 4-dihydro-2H- 1,3-benzoxazine, 4-FP-FBz; 1,3-bis(3-aminopropyl)tetramethyl-disiloxane- benzoxazine, P-BATMSBz ) were synthesized using functional primary amines (N-(4-hydroxyphenyl)maleimide; furfurylamine; 1,3-bis(3-amino- propyl)tetramethyldisiloxane, BATMS) as raw materials. The chemical structures of these benzoxazine mononmers were characterized with FT-IR, 1H NMR, and elemental analysis. Furthermore, a high molecular weight polymer (PBz) possessing reactive benzoxazine groups in the mainchain was prepared through the Diels-Alder reaction using BPA-FBz and a bismale-imide (BMI) as monomers. First, HPM-ABz was prepared from N-(4-hydroxyphenyl)maleimide, formaldehyde, and aniline. HPM-ABz showed a melting point of 52–55℃and good solubility in common organic solvents. HPM-ABz showed a two stage process of thermal polymerization. The first stage arose from the polymerization of maleimide groups, and the second one was the ring-opening reaction of benzoxazine groups. Fusible polymaleimides with a Tg of around 100 °C could be obtained by thermally polymerizing HPM-Ba at 130 °C. Further polymerizing the polymaleimides at 240 °C resulted in a completely cured resin showing a Tg at 204 °C. Good thermal stability and self-extinguishing behavior was observed with the cured polybenzoxazine resins. Second, furan-containing benzoxazine monomers, P-FBz, BPA-FBz, and 4FP-FBz were prepared using furfurylamine as a raw material. Formation of furfurylamine Mannich bridge networks in the polymerizations of P-FBz and BPA-FBz increased the cross-linking densities and thermal stability of the resulting polybenzoxazines. P-FBz and BPA-FBz- based polymers also exhibited high glass transition temperatures above 300℃, high char yields, and low flammability with a limited oxygen index value of 31. The dielectric (Dk3.21–3.39) and mechanical properties (high storage modulus of 3.0–3.9 GPa and low coefficient of thermal expansion of 37.7– 45.4 ppm) of the P-FBz and BPA-FBz-based polymers were superior or comparable to other polybenzoxazines. 4FP-FBz used for polybenzo- xazine modification by means of formation of benzoxazine hybridation with P-FBz. Poly(4FP-FBz) showed low dielectric constant(2.7), and 4FP-FBz incorporation showed significant effect on lowering the dielectric constant of polybenzoxazine. Third, a silicon-containing benzoxazine P-BATMSBz was prepared from 1, 3-bis(3-aminopropyl)tetramethyldisiloxane, BATMS, formaldehyde, and aniline. P-BATMSBz used for polybenzoxazine modification by means of formation of benzoxazine copolymers with P-FBz. P-BATMSBz incorporation exhibited significant effect on toughening polybenzoxazines. It is therefore demonstrated that P-BATMSBz is a high performance modifier to simultaneously enhance the Tg and toughness of polybenzoxazines. Fourth, a high molecular weight polymer (PBz) possessing reactive benzoxazine groups in the mainchain was prepared through the Diels-Alder reaction using BPA-FBz and a bismaleimide (BMI) as monomers. The polymer PBz was further thermally cross-linked to result in a high performance polymer (PBz-R), which exhibits high glass transition temperature of 242 oC, good thermal stability, high mechanical strength, and great flexibility. Another cross-linked polymer curing from the mixture of BPA-FBz and BMI was also prepared. However, the properties of PBz-BR is not as good as what observed with PBz-R. In this work, we focused on improving the properties of polybenzo- xazine. Utilizing the molecular design introduced different functional groups into a series of polybenzoxazines in order to fit the requirement of end use, and to enhance their processability easily, thermal stability, electrical and physical properties. In this study, it was demonstrated that we made contribution to improve the properties of polybenzoxazine as described below:(1) introducing the polymerizable maleimide group into the polybenzoxazine to enhance the crosslink density and reduce the water absorbance of polymaleimide, (2) using economic and ecological furan compound as a raw material in synthesis, to obtain high performance polybenzoxazines, (3) introducing the fluorine and siloxane into the polybenzoxazines as modifier to enhance the toughness and reduce Dk of polybenzoxazines, (4) combining the organic reaction and polymer synthesis, we reported a new approach(using Diels-Alder reaction) for synthesizing polymers having benzoxazine in the main chain.
39
Chang, Che-Yuan, and 張哲淵. "Synthesis and properties of benzoxazine containing fluorene and furan groups and their corresponding polymers." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/54697673768839857309.
Full textAbstract:
碩士中原大學
化學工程研究所
99
In this study,a novel benzoxazine monomer FDP-FBz was synthesized using furfurylamine, formaldehyde and 4,4’-(9-Fluorenylidene) diphenol(FDP) as reactants. The chemical structure of 9,9-Bis(3- furfuryl-3,4-dihydro-2H-1,3- benzoxazinyl)fluorine (FDP-FBz) was characterized with FT-IR, 1H-NMR amd elemental analysis, proving that we synthesized high-purity FDP-FBz monomer successfully. First part, PFBz possessing benzoxazine group in the mainchain was prepared through the Diels-Alder reaction using FDP-FBz and 1,1’-(Methylenedi-4,1-phenylene) bismaleimide (DDM-BMI) as monomers. After thermal ring opening polymerziation, poly(PFBz) showed a high Tg at 360℃, and good thermal stability. Second part, two kind of hyperbranched polymers, TMI-BFBz and TMI-FFBz were prepared from bis(3- furfuryl-3,4-dihydro-2H-1,3-benzoxazinyl) isopropane(BPA-FBz) and Trimaleimidophenyl phosphine oxide(TMPPO), FDP-FBz and TMPPO as monomer, respectively. After thermal ring opening polymerziation, poly(TMI-BFBz)and poly(TMI-FFBz) showed high Tgs at 350℃ and 330 ℃, respectively, and good thermal stability.
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Chu, Wei-cheng, and 朱偉誠. "Synthesis of mesoporous benzoxazine by combination of amphiphilic block copolymers and reaction-induced microphase separation." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/55928656244180294214.
Full textAbstract:
碩士國立中山大學
材料與光電科學學系研究所
100
A series of immiscible crystalline-crystalline diblock copolymers, poly(ethylene oxide)-b-(ε-caprolactone) (PEO-b-PCL), were blended with (3-phenyl-3,4-dihydro-2H-1,3-benzoxazin-6-yl) methanol (Pa-OH). FT-IR analyses provide that the ether group of PEO is a stronger hydrogen bond acceptor than the carbonyl group of PCL with the hydroxyl group of Pa-OH. Pa-OH after curing results in the excluded and confined PCL phase based on differential scanning calorimeter (DSC) analyses. In addition, the mesoporous structure was proved with the increasing the ratio of PCL to PEO in block copolymers by small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) analyses and N2 adsorption-desorption isotherms (BET) The poly(styrene-b-4-vinyl pyridine) diblock copolymer was blended with Pa-OH monomer. FT-IR analyses demonstrate the intermolecular hydrogen bonding interaction between the pyridine group of P4VP and the hydroxyl group of Pa-OH. After curing, the block copolymers were incorporated into polybenzoxazine resin to access the nanostructure through the reaction induced microphase separation mechanism by TEM and SAXS analyses.
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Wang, Meng-Wei, and 汪孟緯. "Steric hindrance-control synthesis of primary amine-containing benzoxazines, and properties of the resulting poly(benzoxazine imide) thermosets." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/04074774186164210367.
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Lee, Kuan-Wei, and 李冠緯. "Synthesis and characterization of low-dielectric crosslinkable phosphinated polyimides and oligo(phenylene oxide)s-containing benzoxazine for high-frequency communication." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/26209866886394738785.
Full textAbstract:
碩士國立中興大學
化學工程學系所
105
Part I. Synthesis and characterization of low-dielectric crosslinkable phosphinated polyimides for high-frequency communication. In the first part of this work, a phosphinated hydroxy diamine was prepared via a one-pot procedure. Based on the phosphinated hydroxy diamine, a series of polyimides with hydroxy linkage in the repeat unit was prepared by thermal imidization. The esterification of hydroxy unit with methacrylic anhydride and cinnamoyl chloride were performed to generate active ester-containing polyimides with methacrylic moiety ( P3-MMA and P4-MMA ) and cinnamoyl moiety ( P3-cin and P4-cin ) in the repeat unit. The other two other active ester-containing polyimides with methacrylic moiety ( B4-MMA and F4-MMA ) in the repeat unit were also prepared for property comparison. The active ester –containing polyimides with active ester act as epoxy harderner for a commercial epoxy resin, HP7200. Epoxy thermosets with high-Tg and moderate-to-low dielectric properties can be achieved. Part II. Synthesis and characterization of oligo(phenylene oxide)s-containing benzoxazine for high-frequency communication. In the second part of this work, a benzoxazine (BZSA90) and polybenzoxazine (PBZSA90) based on a amine-end capped oligo (2,6-dimethyl phenylene) (HSA90), which was prepared from the a phenol-end capped oligo (2,6-dimethyl phenylene) (SA 90). After self-curing or curing with epoxy resin (HP 7200), thermosets with high-Tg and very low dissipation factor can be obtained. Through comparing the data bwteen the BZSA90-cured epoxy thermoset and the SA90-cured epoxy thermoset, we found the Tg was significatnt enhanced, while the good dielectric properties can be maintained.
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賴亭云. "Synthesis and Properties of Thermal Curable Polytriazole with Benzoxazine Moieties in the Main Chain or as Side Chain via Click Reaction." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/41632072671055976607.
Full textAbstract:
碩士國立交通大學
應用化學系碩博士班
99
A series of linear polytriazole-based (PTA) polymers containing thermally curable benzoxazine unit in the main chain or as side chain was synthesized via click reaction. The structure was confirmed by 1H nuclear magnetic resonance (NMR) and fourier transform infrared (FT-IR) spectroscopy. To better understand the curing kinetics of the main-chain and side-chain type polymers, we performed the differential scanning calorimetry (DSC) measurements to describe the thermodynamics of the curing process by using the Kissinger and Ozawa models to calculate the activation energies of PTA-SBz-10 and PTA-MBz-10. This study describes a cross-linked polymer (Cured-PTA-SBz-10) that exhibit dramatic enhancements in thermal properties (117 % improvement in Tg) and mechanical properties (233 % improvement in tensile strength and 260 % improvement in modulus) to compare with neat polytriazole.
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Huang, Yao-Jheng, and 黃耀正. "Synthesis and Characterization of Sulfonated Polytriazole Proton Exchange Membrane for Fuel Cells and Thermally Cured Polytriazole Polymers Incorporating Main or Side Chain Benzoxazine Crosslinking Moieties via “Click Reaction”." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/bmhaqg.
Full textAbstract:
博士國立交通大學
應用化學系碩博士班
101
There are two sections that both of them were using the click chemistry as the tool in this thesis: (i) Synthesize the sulfonated polytriazole proton exchange membrane for fuel cells (ii) Synthesize the thermally cured polytriazole polymers incorporating main or side chain benzoxazine crosslinking moieties (i) Synthesize the sulfonated polytriazole proton exchange membrane for fuel cells Among various types of proton exchange membranes (PEMs) for fuel cells, several nonfluorinated polymeric materials are attracting more attention as alternatives to perfluorinated polymer membranes. The nonfluorinated PEMs can achieve high proton conductivities by introducing high extent of sulfonic acid groups, but tend to deteriorate the mechanical strength and permeability of PEMs simultaneously. The aggregation of conductive sites will cause these PEMs highly swollen or dissolved in aqueous/alcoholic solutions. Crosslinking appears to be an efficient and simple approach to overcome these problems, however, it usually leads to a sacrifice in proton conductivity. In addition, microphase tends separation tends to occur in such crosslinking structure due to contraction of space or incompatibility between hydrophilic (sulfonic acid groups) and hydrophobic (crosslinker) components. The development of more efficient membranes with improved proton conductivity and reduced methanol crossover without detrimentally mechanical and chemical stabilities remains an important challenge. (Part 1) Sulfonated polytriazole (SPTA) in which the acidic sulfonic acid and basic triazole groups act as physical crosslinking sites within a polymer backbone has been successfully prepared, for use as a proton exchange membrane, using the click reaction. The acid-base interactions of the SPTA membranes leads to the formation of well-dispersed ionic clusters and the random distribution of ion channels with good connectivity resulting in lower methanol permeabilities at ambient temperatures and similar or higher proton conductivities than Nafion 117 at 80 °C in conditions of near zero relative humidity. Additionally, the selectivity of SPTA is approximately four times higher than that of Nafion 117, thus it may have potential for use in direct methanol fuel cells (DMFCs). (Part 2) Sulfonated polytriazole-clay (SPTA-clay) nanocomposites are successfully prepared by in situ polymerization of SPTA using click chemistry in the presence of propargyl-functionality modified clay. The clay layers are exfoliated and well dispersed within the SPTA matrix resulting in improvements in thermal stability, mechanical strength, methanol permeatbility, water retention, ion channel size, and ionic cluster distribution. The SPTA-clay nanocomposite membranes with small amounts of clay in the SPTA matrices possess higher selectivity’s; defined as the ratio of proton conductivity to methanol permeability, and thus have potential as proton exchange membranes (PEMs) in direct methanol fuel cells (DMFCs). (ii) Synthesize the thermally cured polytriazole polymers incorporating main or side chain benzoxazine crosslinking moieties (Part 3) Crosslinking is an efficient and simple approach to enhancing the thermal and mechanical properties of polymers. Numerous studies have reported such enhancements by the incorporation of benzoxazine (a cross-linker) in the polymer’s structures. The great majority of the studies have focused on a discussion of the benzoxazine content. As far as we know, there has been no discussion related to effects arising from the position of benzoxazine incorporation. In order to investigate any such effects, we synthesized new benzoxazine monomers (SBz and MBz), containing bis-propargyl functional groups and new main chain and side chain benzoxazine functionalized polytriazole polymers, with the above benzoxazine moieties in the repeat unit, using click chemistry. The resulting thermal and mechanical properties of Cured-PTA-SBz-10 were better than those of Cured-PTA-MBz-10, and the Cured-PTA-SBz-4 and Cured-PTA-SBz-6 were closed or even better than those of Cured-PTA-MBz-10. We assumed that this is attributable to the position effect resulting the differing degrees of polymer crosslinking. To better understand any thermal curing effects related to the positions of benzoxazine moieties in the polymer chain, we performed dynamic DSC measurements by Kissinger and Ozawa methods. Therefore, when designing the polymer, by giving consideration to the position of the cross-linker, the resulting thermal and mechanical properties can be enhanced to the extent that an equivalent polymer can be formed with a reduced amount of cross-linker leading to cost reduction.
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Lamani, Manjunath. "Design And Development Of Synthetic Methods Using Metal-Mediated And Metal Free Redox Reactions : Novel C-H Activations, Reductions And Oxidative Transformations." Thesis, 2012. http://hdl.handle.net/2005/2501.
Full textAbstract:
The thesis entitled “Design and Development of Synthetic Methods using Metal-mediated and Metal-free Redox Reactions: Novel C-H Activations, Reductions and Oxidative Transformations” is presented in 4 chapters
Chapter 1; Iodine catalyzed amination of benzoxazoles: efficient metal free route to 2-aminobenzoxazoles under mild conditions.
The Chapter 1 of this thesis describes iodine catalyzed C-H activation of benzoxazole with primary and secondary amines to form oxidative aminated products. Selective C-H oxidation is a frontline area of modern chemical research as it offers the opportunities to new avenues and more direct synthetic strategies for the synthesis of complex organic molecules.1 In this context, transition metals such as palladium copper, nickel etc, are used extensively for the functional group directed C-H activation, and thus provides new, rapid, low-cost, and environmentally benign protocols for the construction of new chemical bonds.2 During the past two decades iodine and hypervalent iodine have been focus of great attention as they provide mild, chemoselective and environmentally benign strategies in contrast to toxic metal oxidants.3 In this chapter, a facile metal-free route of oxidative amination of benzoxazole with secondary or primary amines in the presence of catalytic amount of iodine (5 mol%) in aq tert-butyl hydroperoxide (1equiv) and AcOH (1.1 equiv) at ambient temperature, under the solvent-free reaction condition is presented. This user-friendly method to form C-N bonds produces tert-butanol and water as the by-products, which are environmentally benign. A wide range of benzoxazole derivatives containing electron-donating and electron-withdrawing groups were coupled with both primary and secondary amines (Scheme 1).
Application of this methodology is demonstrated by synthesizing therapeutically active benzoxazoles by reacting 5-chloro-7-methylbenzoxazole with N-methylpiperazine and N-ethylhomopiperazine to obtain corresponding N-aminatedbenzaxozoles, which exhibit antidiarrhetic activity (Scheme 2).4
Scheme 2
Chapter 2: NIS catalyzed reactions. amidation of acetophenones and oxidative amination of propiophenones
Chapter 2 is divided in to 2 parts. Part 1 describes the synthesis of α-ketoamides by using acetophenone and secondary amine in the presence of N-iodosuccinamide and TBHP in acetonitrile at room temperature, whereas Part 2 reveals the synthesis of 2-aminoketones by reacting aryl alkyl ketones and suitable secondary amine in the presence of NIS and TBHP.
Part 1: Oxidative amidation, synthesis of α-ketoamide:
Alpha α-ketoamides are important intermediates in organic synthesis that are present in a variety of natural products, and pharmaceutically active compounds. Herein, a mild and efficient conversion of acetophenones to α-ketoamide is documented by using aq.TBHP and N-iodosuccinamide (NIS) as a catalyst, at ambient temperature. This amidation reaction was found to be versatile as several aetophenone derivitives containing electron-withdrawing and electron-donating substituents underwent a facile amidation. It was also found that acetyl derivatives of heterocylic compounds could be easily converted to their corresponding ketoamides (few examples are shown in Scheme 3).5 Scheme3
Part 2 of Chapter 2 narrates a novel amination of propiophenone and its derivatives catalysed by NIS in the presence of TBHP to furnish their corresponding 2-aminoketone derivatives (Scheme 4). These derivatives are ubiquitous scaffolds that are present in a wide variety of therapeutic agents. Some of these compounds are used in the treatment of depression, smoking cessation, as monoamine uptake inhibitors, rugs for cancer. They are photoinitiators, precursors to β-aminoalcohols, such as pseudoephedrine analogues. 2-Aminoacetophenone analogues are also important intermediates for the formation of several heterocyclic compounds and are active moieties in several important drugs such as ifenprodil,
Scheme 4.
Chapter 3: Efficient oxidation of primary azides to nitriles
This Chapter is divided in to 2 parts, which presents the oxidation of primary azides to their corresponding nitriles.
Part 1: An Efficient oxidation of primary azides catalyzed by copper iodide: a convenient method for the synthesis of nitriles
In Part 1, an efficient oxidation of primary azides catalyzed by copper iodide to their corresponding nitriles is reported. Herein, the oxidation of primary azide to nitrile is performed using catalytic amount of copper iodide, and aq TBHP in water at 100 ° C. This methodology is compatible with a wide range of primary benzylic azides that contain electron-donating and electron-withdrawing functional groups. The oxidation was found to be selective and a number of oxidizable functional groups were well-tolerated during the reaction conditions (few examples are shown in Scheme 5).6
Scheme 6
Furthermore, oxidation of secondary azides furnished the corresponding ketones in excellent yields (Scheme 6).6
In the Part 2 of Chapter 3, a non-metal catalysed oxidation of primary azides to nitriles at ambient temperature is reported. This part reveals the oxidation of primary azides to nitriles by employing catalytic amounts of KI (25 mol%), DABCO (25 mol%) and aq. TBHP (3 equiv., 70% solution in water). This reaction provides a good selectivity, as double and triple bonds were not oxidized under the reaction conditions. Additionally, chemoselective oxidation of benzylicazides against aliphatic azides increases the potential application of the present method (Scheme 7).7
Chapter 4: Chemoeselective reduction of olefins
Part 1: Iron chloride catalysed aerobic reduction of olefins using aqueous hydrazine at ambient temperature
Chapter 4 describes the reduction olefins and acetylenes, which is presented in two Parts. Part 1 documents utility of hydrazine (1.5 equiv) for the chemoselective reduction of nonpolarised carbon-carbon bond using iron catalysts. In this part, a chemoselective reduction of alkenes and alkynes in the presence of a variety of reducible functional groups is demonstrated (Scheme 8). The highlight of the present method is that the reduction proceeds well at room temperature and requires only 1.5 equiv of hydrazine hydrate. The olefin reduction by hydrazine depends upon the controlled release of diimide during the reduction. Generally, metal catalyzed reduction of olefins employ a large excess of hydrazine (10-20 equiv), which might be attributed to uncontrolled release of diimide during the reduction.8
Scheme 8
Part 2: Guanidine catalyzed aerobic reduction: a selective aerobic hydrogenation of olefins using aqueous hydrazine
In Chapter 4, part 2, organocatalytic generation of diimide and its utility to reduce the double bonds is presented. Generation of diimide in situ by using organo catalysts and its use for the reduction of carbon-carbon double bond is one of the interesting topics in organic chemistry. It has been shown in this part of the thesis that the reduction of olefin at room temperature can be efficiently performed by using 10 mol% of guanidine nitrate, 2 equiv of aqueous hydrazine in oxygen atmosphere. This method tolerates a variety of reducible functional groups such as nitro, azido, and bromo and protective groups such as methyl ethers, benzyl ethers, and Cbz groups. It is also shown that terminal olefin can be selectively reduced in the presence of internal olefin (Scheme 9). Unlike other methods that employ diimide strategy, the present method is shown to be efficient in reducing substrates those contain internal double bonds such as cinnamyl alcohol and its derivatives