No description available.

The introductory chapter reviews the current state of mechanistic understanding of the hexadehydro-Diels-Alder (HDDA) reaction. With the rapid development of the HDDA reaction from its first discovery in 1997, the question of whether a concerted or stepwise mechanism better describes the thermally activated formation of ortho-benzyne from a diyne and a diynophile has been debated. Mechanistic and kinetic investigations were able to show that this is not a black or white situation, as minor changes can tip the balance. In chapter 2 of this thesis, the catalytic process leading from 1,11-bis(p-tolyl)undeca-1,3,8,10-tetrayne to fully-substituted naphthalene and azulene derivatives, by two different platinum-catalyzed dimerization pathways, was investigated. In chapter 3, the cannibalistic self-trapping reaction of an ortho-benzyne derivative generated from 1,11-bis(p-tolyl)undeca-1,3,8,10-tetrayne in an HDDA reaction was investigated. Without adding any specific trapping agent, the highly reactive benzyne is trapped by another bisdiyne molecule in at least three different modes. In chapter 4 direct UV/VIS spectroscopic evidence for the existence of an o-benzyne in solution is reported, and the dynamics of its formation in a photo-induced reaction are established. For this purpose, 1,11-bis(p-tolyl)undeca-1,3,8,10-tetrayne was investigated, using femtosecond transient absorption spectroscopy in the ultraviolet/visible region. In chapter 5, following the isolation and characterization of the reaction products discussed in chapter 3, further species resulting from reactions of the highly reactive ortho-benzyne derivative were identified. / Das einleitende Kapitel gibt einen Überblick über den aktuellen Stand des mechanistischen Verständnisses der Hexadehydro-Diels-Alder (HDDA)-Reaktion. Mit der rasanten Entwicklung der HDDA-Reaktion seit ihrer ersten Entdeckung im Jahr 1997 wurde die Frage diskutiert, ob ein konzertierter oder ein schrittweiser Mechanismus die thermisch aktivierte Bildung von ortho-Benzin aus einem Diin und einem Diinophil besser beschreibt. Mechanistische und kinetische Untersuchungen konnten zeigen, dass es sich hierbei nicht um eine Schwarz-Weiß-Situation handelt, da schon kleine Änderungen das Gleichgewicht verändern können. In Kapitel 2 dieser Arbeit wurde der katalytische Prozess, der von 1,11-Bis(p-tolyl)undeca-1,3,8,10-tetrain zu vollständig substituierten Naphthalin- und Azulen-Derivaten führt, über zwei verschiedene platinkatalysierte Dimerisierungspfade untersucht. In Kapitel 3 wurde die kannibalistische Selbsteinfangreaktion eines ortho-Benzin-Derivats untersucht, das aus 1,11-Bis(p-tolyl)undeca-1,3,8,10-tetrain in einer HDDA-Reaktion erzeugt wurde. Ohne Zugabe eines spezifischen Einfangmittels wird das hochreaktive Benzin von einem anderen Bisdiin-Molekül in mindestens drei verschiedenen Modi eingefangen. In Kapitel 4 wird der direkte UV/VIS-spektroskopische Nachweis für die Existenz eines o-Benzins in Lösung berichtet und die Dynamik seiner Bildung in einer photoinduzierten Reaktion aufgezeigt. Zu diesem Zweck wurde 1,11-Bis(p-tolyl)undeca-1,3,8,10-tetrayne mittels Femtosekunden-Transienter-Absorptionsspektroskopie im ultravioletten/sichtbaren Bereich untersucht. In Kapitel 5 wurden nach der Isolierung und Charakterisierung der in Kapitel 3 diskutierten Reaktionsprodukte weitere Spezies identifiziert, die aus Reaktionen des hochreaktiven ortho-Benzin-Derivats resultieren.

No description available.

No description available.

Diels-Alder polyphenylenes (DAPPs) are chemically and thermally stable polymers, used for dielectric resins, gas separation membranes, and fuel cell proton exchange membranes. Highly fluorinated DAPPs are expected to have better thermal stability and chemical resistance, higher glass transition temperatures, improved compatibility with other fluorinated polymers (like NafionTM), and better adhesion to certain surfaces such as some metals. This thesis proposes a synthesis of highly fluorinated DAPPs by reacting novel, fluorinated bis-cyclopentadienone (CPD) monomers with known aromatic dialkynes. This thesis starts with an introduction to DAPP synthesis, properties, and applications. The second chapter focuses on the synthesis of 4,4′-bis[1,2,4-tris(perfluoro-4-tolyl)cyclopentadien-5-one-3-yl]octafluorobiphenyl (CPD monomer). In the first step, disodiumbis(cyclopentadieny)octafluorobiphenyl was combined with 6 equivalents of octafluorotoluene in HMPA to give 4,4′-bis[1,2,4-tris(perfluoro-4-tolyl)cyclopentadiene-3-yl]octafluorobiphenyl. Oxidation to the corresponding diketone was effected using selenium dioxide. The synthesis of CPD monomer presented several unexpected challenges that were ultimately overcome. The third chapter describes a series of initial polymerization experiments as well as some model reactions that were carried out to understand monomer reactivity. Finally the future research plan of synthesizing different polymers by Diels-Alder reaction and nucleophilic substitution reaction has been discussed. / Master of Science

Devido à sua intensa absorção de luz na região visível do espectro, as porfirinas e seus derivados (clorinas e bacterioclorinas) são de grande importância na terapia fotodinâmica (TFD) para o tratamento de doenças neoplásicas. Neste trabalho foram sintetizadas as novas vinil-porfirinas estrategicamente funcionalizadas (47 e 48), seguida de uma sistemática de reações de Diels-Alder com dieófilos ativados, com o propósito de obter clorinas e/ou bacterioclorinas para potenciais aplicações em TFD. / Due to their strong absorption in the visible region, porphyrins and related derivatives (chlorins and bacteriochlorins) are very important in photodynamic therapy (PDT) for the treatment of neoplasic diseases. In this work were synthesized the novel and strategically functionalizated vinyl-porphyrins 47 and 48, followed by systematic Diels-Alder reactions with activated dienophiles to obtain chlorins and/or bacteriochlorins, potentially useful on PDT.

O objetivo deste trabalho foi iniciar o estudo de uma nova metodologia sintética para a obtenção do sistema 11-oxabiciclo[6.2.1]undecano, o esqueleto estrutural básico de uma classe de produtos naturais conhecidos como furanoeliangolidos. A abordagem sintética proposta envolveria a formação de um composto bicíclico através da reação de Diels-Alder com derivados de furano, seguida pela formação de um hexanel e, finalmente, ruptura de uma ligação central para formação do sistema macrocíclico. Além disso, a reação de Diels-Alder entre derivados de furano e acetileno dará origem a compostos que apresentam como esqueleto estrutural o sistema 7-oxabiciclo[2.2.1]heptano, que podem ser utilizados como material de partida para a síntese de diversos produtos naturais. Iniciamos este estudo com a reação de Diels-Alder entre o 3,4-dimetoxi-2-metil furano e o bromopropiolato de metila, onde foi obtido o produto 85, que após algumas modificações deu origem ao composto 92. Entretanto, após inúmeras tentativas não conseguimos transformar o composto 92 no triciclo desejado. Para evitar essas transformações que se mostraram problemáticas, resolvemos estudar a reação de Diels-Alder entre derivados de furano e benzoquinonas 2,5-dissubstituídas, que dará origem aos adutos devidamente funcionalizados para serem transformados no derivado do sistema 11-oxabiciclo [6.2.1]undecano. No entanto, após o estudo dessas reações de cicloadição, observamos que elas têm o equilíbrio fortemente deslocado no sentido dos materiais de partida. Por esse motivo, a continuidade desta metodologia sintética mostrou ser inviável. Iniciamos então, um estudo da reação de Diels-Alder entre os diverso derivados de furanos e acetilenos. Após o estudo dessas reações de Diels-Alder foi possível verificar que a maioria dos adutos derivados dos furanos é instável no meio reacional. Os melhores resultados obtidos nessas reações de Diels-Alder foram usando o acetilenodicarboxilato de dimetila como dienófilo. Os adutos obtidos são intermediários importantes e bem funcionalizados, que podem ser utilizados na continuidade do estudo de desenvolvimento de nova metodologia sintética para a obtenção do sistema 11-oxabiciclo[6.2.1]undecano / The aim of this work was to start the study of a new methodology to synthesize the 11-oxabicycle[6.2.1]undecane system, the main carbon skeleton of the furanoheliangolides. The proposed synthetic approach involves the preparation of a bicyclic compound through a Diels-Alder reaction with furan derivatives, followed by formation of a six membered ring and, finally, cleavage of the central bond to obtain of the macrocyclic system. The Diels-Alder reaction between furan and acetylene derivatives gives a compound with the 7-oxabicyclico[2.2.1]heptane system, that is a potential starting material for the synthesis of several natural products. We started this study with the Diels-Alder reaction between the 3,4-dimethoxy-2-methylfuran and methyl bromopropiolate, and obtained the product 85 that after some modifications furnished the compound 92. However, after various attempts we were unable to convert the compound 92 into the desired tricycle. We have then decided to study the Diels-Alder reaction between furan and 2,5-disubstituted benzoquinone derivatives, that could furnish the adducts properly functionalized to be transformed in the 11-oxabicyclico[6.2.1]undecane system. However, we observed that the equilibrium is strongly shifted towards the starting materials in these cycloaddition reactions. This methodology has thus showed to be impracticable. As a third alternative, we affected the study the Diels-Alder reaction between the furans derivatives and the acetylenes. The adducts obtained present 7-oxabicyclico[2.2.1]heptane system that could be used to synthesizes of structural skeleton of furanoheliangolide.

Quando o tetrafluoroborato de N-(α-carbometoximetil)-2,4,6-trifenilpiridínio (Ia) foi tratado com hidróxido de potássio em etanol, resultou uma betaína que, ao ser aquecida na presença de benzaldeído ou p-clorobenzaldeído, não produziu a esperada oxazolidina IIa. Em lugar desta 1,2-di-hidropiridina, formou-se um sal cujo cátion correspondia à estrutura de um N-metil-2,4,6-trifenilpiridínio (III). Este composto resultaria da protonação da ilida intermediária, formada pela descarboxilação da betaína. Porém, quando o mesmo tipo de reação foi efetuada com o derivado α-metilado Ib, o espectro de RMN de H do produto bruto indicou a formação da di-hidropiridina (IIb), na forma de 4 estereoisômeros. A oxazolidina IIa, como um isômero largamente majoritário, pôde ser obtida pela reação do tetrafluoroborato de N-metil-2,4,6-trifenilpiridínio (III) com p-clorobenzaldeído, na presença de uma solução diluída de álcali. Esta oxazolidina era bastante instável e não pode ser purificada, sendo submetida na forma bruta à reação de Diels-Alder com a N-metil-maleimida. Esta reação conduziu a dois adutos isoméricos (IV e V). Embora o aduto majoritário (V) fosse estável em solução de deutero-clorofórmio, o aduto minoritário (IV), na presença desse solvente e à temperatura ambiente, isomerizava-se após algumas horas. A estrutura dos três adutos foi determinada por experimentos de RMN de H (NOESY e NOE 1D seletivo). A adição de um pequeno volume de solução diluída de ácido clorídrico aos compostos IV e V, dissolvidos em acetonitrila e à temperatura ambiente, resultou na isomerização catalítica desses adutos. Porém, quando esta reação de protonação foi efetuada sob refluxo de acetonitrila, formaram-se dois produtos (VI e VII), cuja estrutura era compatível com ocorrência de uma reação de retro-aza Diels-Alder. Finalmente, foi estudado o equilíbrio conformacional de dois novos sais de 2,4,6-trifenil- piridínio, e os resultados foram comparados com aqueles obtidos para os sais análogos 2,4,6-trimetil-substituídos. / When the tetrafluoroborate of N-(α-carbomethoxymethyl)-2,4,6-triphenylpridinium (Ia) was submitted to alkaline hydrolysis followed by decarboxylation upon heating, the resulting betaine failed to undergo the aldol addition reaction with aromatic aldehydes leading, in lieu of the expected oxazolidine (IIa),a salt bearing the cation N-methyl-2,4,6-triphenylpyridinium (III), as a result of the easy protonation of the intermediate ylide. However, for the corresponding a-methylated salt (Ib), the formation of four stereoisomeric 1,2- dihydropiridines was confirmed by inspection of the H NMR of the crude product. As an alternative to this method for obtaining IIa, a mixture of III and p-chlorobenzaldehyde was stirred at room temperature for several hours, in the presence of a diluted aqueous alkali. The resulting 1,2-dihidropyridine (IIa) was rather unstable precluding its isolation from the crude product mixture, and was submitted, without further purification, to the Diels-Alder reaction with Nmethylmaleimide, leading to two diastereomeric isoquinuclidines (IV) and (V). Although the major isomer showed to be stable in a deuterochloroform solution, the minor isomer (IV) underwent a spontaneous isomerization, upon standing in such solvent at room temperature. The stereochemical features of these three aducts could be accessed by NOESY and 1D NOE selective H NMR experiments. By treating a solution of adducts IV and V in acetonitrile with a small volume of aqueous HCl, at room temperature, an acid catalyzed isomerization took place. However, when the protonation reaction of the major diastereoisomer (V) was performed in acetonitrile at the reflux temperature, two products (VI and VII) were isolated, highlighting the occurrence of a retro-aza Diels Alder reaction. Finally, the conformation equilibria for two new 2,4,6-triphenyl- pyridinium salts was investigated. Results were correlated with previous ones referring to analogous 2,4,6-trimethyl- salts.

Quando o tetrafluoroborato de N-(α-carbometoximetil)-2,4,6-trifenilpiridínio (Ia) foi tratado com hidróxido de potássio em etanol, resultou uma betaína que, ao ser aquecida na presença de benzaldeído ou p-clorobenzaldeído, não produziu a esperada oxazolidina IIa. Em lugar desta 1,2-di-hidropiridina, formou-se um sal cujo cátion correspondia à estrutura de um N-metil-2,4,6-trifenilpiridínio (III). Este composto resultaria da protonação da ilida intermediária, formada pela descarboxilação da betaína. Porém, quando o mesmo tipo de reação foi efetuada com o derivado α-metilado Ib, o espectro de RMN de H do produto bruto indicou a formação da di-hidropiridina (IIb), na forma de 4 estereoisômeros. A oxazolidina IIa, como um isômero largamente majoritário, pôde ser obtida pela reação do tetrafluoroborato de N-metil-2,4,6-trifenilpiridínio (III) com p-clorobenzaldeído, na presença de uma solução diluída de álcali. Esta oxazolidina era bastante instável e não pode ser purificada, sendo submetida na forma bruta à reação de Diels-Alder com a N-metil-maleimida. Esta reação conduziu a dois adutos isoméricos (IV e V). Embora o aduto majoritário (V) fosse estável em solução de deutero-clorofórmio, o aduto minoritário (IV), na presença desse solvente e à temperatura ambiente, isomerizava-se após algumas horas. A estrutura dos três adutos foi determinada por experimentos de RMN de H (NOESY e NOE 1D seletivo). A adição de um pequeno volume de solução diluída de ácido clorídrico aos compostos IV e V, dissolvidos em acetonitrila e à temperatura ambiente, resultou na isomerização catalítica desses adutos. Porém, quando esta reação de protonação foi efetuada sob refluxo de acetonitrila, formaram-se dois produtos (VI e VII), cuja estrutura era compatível com ocorrência de uma reação de retro-aza Diels-Alder. Finalmente, foi estudado o equilíbrio conformacional de dois novos sais de 2,4,6-trifenil- piridínio, e os resultados foram comparados com aqueles obtidos para os sais análogos 2,4,6-trimetil-substituídos. / When the tetrafluoroborate of N-(α-carbomethoxymethyl)-2,4,6-triphenylpridinium (Ia) was submitted to alkaline hydrolysis followed by decarboxylation upon heating, the resulting betaine failed to undergo the aldol addition reaction with aromatic aldehydes leading, in lieu of the expected oxazolidine (IIa),a salt bearing the cation N-methyl-2,4,6-triphenylpyridinium (III), as a result of the easy protonation of the intermediate ylide. However, for the corresponding a-methylated salt (Ib), the formation of four stereoisomeric 1,2- dihydropiridines was confirmed by inspection of the H NMR of the crude product. As an alternative to this method for obtaining IIa, a mixture of III and p-chlorobenzaldehyde was stirred at room temperature for several hours, in the presence of a diluted aqueous alkali. The resulting 1,2-dihidropyridine (IIa) was rather unstable precluding its isolation from the crude product mixture, and was submitted, without further purification, to the Diels-Alder reaction with Nmethylmaleimide, leading to two diastereomeric isoquinuclidines (IV) and (V). Although the major isomer showed to be stable in a deuterochloroform solution, the minor isomer (IV) underwent a spontaneous isomerization, upon standing in such solvent at room temperature. The stereochemical features of these three aducts could be accessed by NOESY and 1D NOE selective H NMR experiments. By treating a solution of adducts IV and V in acetonitrile with a small volume of aqueous HCl, at room temperature, an acid catalyzed isomerization took place. However, when the protonation reaction of the major diastereoisomer (V) was performed in acetonitrile at the reflux temperature, two products (VI and VII) were isolated, highlighting the occurrence of a retro-aza Diels Alder reaction. Finally, the conformation equilibria for two new 2,4,6-triphenyl- pyridinium salts was investigated. Results were correlated with previous ones referring to analogous 2,4,6-trimethyl- salts.

Ce travail de thèse porte sur la synthèse et la caractérisation d’élastomères réticulés réversiblement à base de polyisoprène et polybutadiène en vue de leur possible recyclage. Pour se faire, de longues chaines de polydiènes 1,4-cis ont été dégradées de manière contrôlée afin d’obtenir des polymères à faible viscosité. Dans un second temps, ces polydiènes ont ensuite été modifiés chimiquement soit le long ou soit aux extrémités des chaines afin d’obtenir des fonctions réactives de type alcool. Ces fonctions hydroxyles ont ensuite servi de point d’ancrage pour le greffage de fonctions furanes. L’addition d’un composé de type bis-maléimide au polymère liquide a alors conduit à la formation d’élastomère réticulé thermo-réversiblement grâce à la réaction de Diels-Alder entre les groupements furanes et maléimides. Les matériaux ainsi obtenus se comportement comme un élastomère réticulé stable dans une large gamme de température (- 80 °C à + 130 °C). Les propriétés mécaniques de ces élastomères (module de Young, contrainte/élongation à la rupture, module caoutchoutique) peuvent être facilement modulées en modifiant plusieurs paramètres comme la longueur des chaines, la densité de réticulation ou le lieu de réticulation (bout des chaines ou le long des chaines. La recyclabilité des matériaux a ensuite été montrée, aucune perte de propriétés n’a été observée même après 5 cycles de recyclage. Enfin, en changeant le type de liens réversibles par des groupements ureidopyrimidinones (UPy), nous avons observé que le matériel réticulé réversiblement par liaisons hydrogène obtenu possédait une organisation supramoléculaire particulière, induite par l’assemblage des groupements UPy. / This work focuses on the synthesis and characterization of reversibly crosslinked polyisoprene and polybutadiene and their potential recyclability. To this end, long chains of 1,4-cis polydienes have been degraded in a controlled manner in order to obtain telechelic polymers with low viscosity. In a second step, these low molar mass polydienes were chemically modified either along the backbone or at the chain-end of the polymer in order to obtain reactive functions. The thus obtained hydroxyl functions have been used as an anchor point for the grafting of furan functions. The addition of a bis-maleimide compound to the liquid polymer led to the formation of thermo-reversibly crosslinked elastomer thanks to the Diels-Alder reaction between the furan and the maleimide groups. The obtained materials have the behavior of a crosslinked elastomer, stable in a wide temperature range (-80 °C to + 130 °C). The mechanical properties of these elastomers (Young's modulus, strain / elongation at break, rubber modulus) can be easily modulated by modifying several parameters such as chain length, crosslinking density or crosslinking site along the chains. The recyclability of the materials was shown as no properties loss was observed even after 5 cycles of recycling. Finally, by changing the furan groups by ureidopyrimidinone groups (UPy), the reversibly crosslinked material obtained through hydrogen bonds possessed a totally different behavior with a particular supramolecular organization, induced by the assembly of the UPy groups.