Dissertations / Theses: 'Diels-Alder cycloaddition reactions'

1

Chumachenko, Natasha. "[Beta]-acryloyloxysulfonyl tethers for intramolecular Diels-Alder cycloaddition reactions." [Kent, Ohio] : Kent State University, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=kent1135392557.

Full text

Abstract:

Thesis (Ph.D.)--Kent State University, 2005.
Title from PDF t.p. (viewed July 28, 2005). Author's first name appears on the abstract page as: Nataliya. Advisor: Paul Sampson. Keywords: b-hydroxysulfones; [beta]-hydroxysulfones; epoxide opening; intramolecular Diels-Alder reaction; vinylsulfones. Includes bibliographical references (p.194- 202).

APA, Harvard, Vancouver, ISO, and other styles

2

Chumachenko, Nataliya. "b-Acryloyloxysulfonyl Tethers for Intramolecular Diels-Alder Cycloaddition Reactions." Kent State University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=kent1135392557.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Shengxian, Zhao. "Cycloaddition reactions of meso-tetraarylporphyrins." Doctoral thesis, Universidade de Aveiro, 2005. http://hdl.handle.net/10773/4871.

Full text

Abstract:

Doutoramento em Química
O trabalho apresentado nesta dissertação descreve o comportamento de meso-tetra-arilporfirinas em reacções de ciclo-adição e suas possíveis aplicações na síntese de novas porfirinas com grupos policíclicos aromáticos (“π-extended porphyrins”). No capítulo 1 apresenta-se uma revisão das aplicações de porfirinas e compostos afins e também das reacções de ciclo-adição que envolvem ligações duplas (periféricas) do macrociclo. O capítulo 2 descreve o trabalho feito em reacções de cicloadição 1,3-dipolar de meso-tetra-arilporfirinas com iletos de azometino. Considerou-se primeiramente a reactividade de meso-tetra-arilporfirinas simétricas perante iletos de azometino. Em seguida estudaram-se as reacções de meso-tetra-arilporfirinas de tipo A3B também com iletos de azometino. Seguidamente consideraram-se estudos similares mas desta vez visando reacções de cicloadição 1,3-dipolar, intramolecular, com meso-(o-formilfenil)porfirinas. O capítulo 3 descreve os estudos efectuados sobre transformações de Diels-Alder de meso-tetra-arilporfirinas com orto-quinodimetano de tipo pirazínico. Os novos produtos (“π-extended porphyrins”) obtiveram-se por ciclização intramolecular entre grupos meso-arilo e o anel quinoxalínico fundido em β. No capítulo 4 descrevem-se os estudos de ciclo-adição 1,3-dipolar de iletos N-piridínicos contendo o macrociclo porfirínico. As reacções de tais iletos com quinonas e com acetilenodicarboxilato de dimetilo originaram porfirinas subsituidas em posição meso com grupos de tipo indolizina. Essas quinonas foram usadas em excesso, actuando como dipolarófilos iniciais e depois como oxidantes. Obtiveram-se novos compostos aromáticos policíclicos nas reacções daqueles iletos com alcenos electronicamente deficientes e na ausência de oxidante. O capítulo 5 relata os resultados dos estudos de síntese de porfirinas com grupos policíclicos aromáticos através de reacções electrocíclicas. Isso foi conseguido a partir das reacções de porfirinas contendo grupos cetónicos com iletos de fósforo. A caracterização estrutural destes novos derivados fez-se recorrendo ao uso de técnicas espectroscópicas modernas, especialmente através de estudos de RMN. Estes métodos de RMN incluíram métodos mono e bidimensionais (1D: 1H, 13C, DEPT; 2D: COSY, NOESY, HSQC, HMBC).
The work presented in this dissertation describes the cycloaddition reaction studies concerning meso-tetraarylporphyrins and also their applications in the synthesis of novel π-extended porphyrins. Chapter 1 is a review on the applications of porphyrin derivatives and also on the cycloaddition reactions involving the peripheral double bonds of porphyrins. Chapter 2 is related with the 1,3-dipolar cycloaddition reactions of meso-tetraarylporphyrins with azomethine ylides. Firstly, the reactivities of symmetrical meso-tetraarylporphyrins in the reactions with azomethine ylides were investigated; secondly, the 1,3-dipolar cycloaddition reactions of A3B type meso-tetraarylporphyrins with azomethine ylides were also carried out; thirdly, the intramolecular 1,3-dipolar cycloaddition reactions of meso-(o-formylphenyl)porphyrins were also studied. Chapter 3 is related with Diels-Alder reactions of meso-tetraarylporphyrins with pyrazine ortho-quinodimethane. The novel π-extended porphyrins were obtained from the intramolecular ring closure reactions between the meso-aryl group and the β-fused quinoxaline ring. Chapter 4 is related with 1,3-dipolar cycloaddition reactions of porphyrinic pyridinium N-ylides. The reactions of porphyrinic pyridinium N-ylides with quinones and dimethyl acetylenedicarboxylate afford meso-substituted indolizine porphyrins. The quinones were used in excess, acting as dipolarophiles and as oxidants. The novel polycyclic aromatic compounds were obtained from the reactions of porphyrinic pyridinium N-ylides with the electron-deficient alkenes in the absence of any oxidant. Chapter 5 is related with the synthesis of polycyclic aromatic porphyrin analogues via electrocyclic reactions.These novel analogues were synthesized from the reactions of ketone-bridged porphyrins with phosphorus ylides. For the structural characterizations of the new compounds modern analytical techniques were used, with a special emphasis on NMR spectroscopic studies. These NMR methods include 1D: 1H, 13C, DEPT; 2D: COSY, NOESY, HSQC, HMBC.

APA, Harvard, Vancouver, ISO, and other styles

4

MacNevin, Christopher J. "Reactivity of substituted 4-Pyridones in normal and inverse demand Diels-Alder cycloaddition /." Electronic version (PDF), 2003. http://dl.uncw.edu/etd/2003/macnevinc/christophermacnevin.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Nagare, A. S. "Physical - organic aspects of diels - alder reactions in eutectic and other environmental benign media." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2016. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/5884.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Compain-Batissou, Cudel Muriel. "SYNTHESE DE NOUVELLES QUINONES HETEROCYCLIQUES PAR APPLICATION DES REACTIONS DE CYCLOADDITIONS DE DIELS-ALDER ET 1,3-DIPOLAIRE. EVALUATION IN VITRO DE LEUR ACTIVITE SUR TOXOPLASMA GONDII." Phd thesis, Université Claude Bernard - Lyon I, 2007. http://tel.archives-ouvertes.fr/tel-00281991.

Full text

Abstract:

La toxoplasmose est une anthropozoonose ubiquitaire causée par Toxoplasma gondii. Malgré de nombreuses recherches, l'arsenal thérapeutique reste très restreint. L'objectif des travaux présentés dans ce mémoire est la synthèse de carbazolequinones et l'évaluation de leur efficacité sur T. gondii. Les carbazolequinones naturelles comme les calothrixines ont des propriétés antiparasitaires et cytotoxiques. La synthèse de para- et ortho-quinones de type benzo-, isoxazolo- et triazolo-carbazolequinones a été réalisée par application des réactions de cycloaddition [4+2] ou 1,3-dipolaires régiosélectives. La stratégie de synthèse à partir de dipolarophiles monobromés permet en effet, d'accéder sélectivement au régioisomère souhaité. Les attributions de structure des régiosiomères ont été confirmées par RMN 1H NOE et par une étude des corrélations 1H -13C HMBC. Concernant l'évaluation biologique in vitro, les composés inhibent la croissance de T. gondii comme la sulfadiazine et la pyriméthamine, avec une cytotoxicité sur les cellules myélomonocytiques THP1. Aucun des composés synthétisés n'inhibent la PNP, enzyme clé de la voie de sauvetage des purines, seule voie d'accès pour le parasite aux bases puriques. L'inhibition de la croissance de T. gondii par nos composés n'est pas liée directement liée à l'inhibition de la PNP.

APA, Harvard, Vancouver, ISO, and other styles

7

Banert, Klaus, Sandra Bochmann, Andreas Ihle, Oliver Plefka, Florian Taubert, Tina Walther, Marcus Korb, Tobias Rüffer, and Heinrich Lang. "Synthesis with Perfect Atom Economy: Generation of Furan Derivatives by 1,3-Dipolar Cycloaddition of Acetylenedicarboxylates at Cyclooctynes." Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-152891.

Full text

Abstract:

Cyclooctyne and cycloocten-5-yne undergo, at room temperature, a 1,3-dipolar cycloaddition with dialkyl acetylenedicarboxylates 1a,b to generate furan-derived short-lived intermediates 2, which can be trapped by two additional equivalents of 1a,b or alternatively by methanol, phenol, water or aldehydes to yield polycyclic products 3b–d, orthoesters 4a–c, ketones 5 or epoxides 6a,b, respectively. Treatment of bis(trimethylsilyl) acetylenedicarboxylate (1c) with cyclooctyne leads to the ketone 7 via retro-Brook rearrangement of the dipolar intermediate 2c. In all cases, the products are formed with perfect atom economy.

APA, Harvard, Vancouver, ISO, and other styles

8

Alves, Jessica. "Advanced photochemical reaction systems for molecular design." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/227734/1/Jessica_Alves_Thesis.pdf.

Full text

Abstract:

Direct laser writing is a technique for printing complex 3D structures with high resolution by irradiating a photoresist in a two-photon process. Improved resolution and dynamic material properties of the printed structures is critical. Herein, advanced photochemical systems were investigated, potentially enabling dual-wavelength direct laser writing. Such systems consisting of organic photoswitches enable the formation of a single product only when irradiated with two wavelengths. A well-known class of photoswitches was investigated for this purpose and its chemistry was carefully explored. Further, photocatalysis combined with a photoswitch was identified as a possible strategy for the two-colour activated photoresist development.

APA, Harvard, Vancouver, ISO, and other styles

9

Bennes, Raphael Michel. "Recognition-induced control and acceleration of Diels-Alder cycloadditions." Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368517.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Wijnen, Jan Willem. "Cycloadditions in aqueous media." [S.l. : [Groningen] : s.n.] ; [University Library Groningen] [Host], 1997. http://irs.ub.rug.nl/ppn/159343356.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Pepper, Adrian Gordon. "Asymmetric synthesis using acyl-nitroso cycloadditions : applications to natural product synthesis." Thesis, University of Salford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314011.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Schmitt, Gérard. "Réactions de l'hydrofluoroborate d'un composé de Reissert sur divers alcenes : Compétition entre cycloaddition dipolaire-1,3 et cycloaddition de Diels-Alder." Besançon, 1987. http://www.theses.fr/1987BESA2041.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Weisbrod, Samuel Hieronymus [Verfasser]. "Catalyst-free chemoselective DNA conjugation by the Staudinger ligation and Diels Alder cycloaddition reaction / Samuel Hieronymus Weisbrod." Konstanz : Bibliothek der Universität Konstanz, 2010. http://d-nb.info/1022323741/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Sancibrao, Pierre. "Cycloadditions de nitroso Diels-Alder asymétriques et régiosélectives : une nouvelle voie synthétique d'hétérospirocycles." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112417.

Full text

Abstract:

Au cours de ce projet de recherche, nous nous sommes intéressés à la synthèse de motifs hétérospiraniques énantioenrichis. De ce fait, notre équipe a pu élaborer une nouvelle voie synthétique pouvant conduire à la synthèse de molécules possédant des structures bicycliques spiraniques diverses. Cette voie de synthèse inédite est articulée sur une réaction de nitroso Diels-Alder. Le contrôle de la stéréosélectivité ainsi que le contrôle de la régiosélectivité, peu décrit dans la littérature, ont été spécifiquement étudiés lors de ces travaux. Nos différentes études ont permis de mieux appréhender ces aspects de la réaction de nitroso Diels-Alder. Deux approches différentes ont d’ailleurs été développées au cours de ces travaux. Celles-ci ont toutes deux conduit a un contrôle total de la régiosélectivité de cette cycloaddition. Les cycloadditions réalisées par une réaction utilisant un diénophile de type nitrosopyridine et catalysées par une source de cuivre chiral ont conduit aux cycloadduits précurseurs d’azaspirobicycles avec une énantiosélectivité modeste. D’autres cycloadditions utilisant un dienophile chiral de type chloronitroso dérivé du D-xylose ont permis la synthèse de précurseurs de bicycles oxaspiraniques avec des excès énantiomériques supérieurs à 95%. Cette dernière approche a permis la synthèse de spiroethers par une réaction d’ouverture de liaison N-O ainsi qu’une réaction de substitution nucléophile intramoléculaire, tandis que des spirolactones ont été obtenus par oxydation du diol résultant de l’ouverture de la liaison N-O. La fonctionnalisation de ces structures a été possible en engageant leur fonction vinyl triflate dans des couplages de Suzuki. Il a ainsi été possible de synthétiser 9 structures différentes oaxaspiraniques dont 5 de façons énantiosélectives
During this research, we were interested in the synthesis of enantiopur heterospiranic bicycles. We therefore developed a new synthetic route towards the synthesis of molecules with different spirocyclic structures. This novel synthetic route features a nitroso Diels-Alder cycloaddition as key step. The total control of the stereoselectivity and the regioselectivity of the reaction, rarely described in the literature, have been specifically studied during this work. This study allows us to have a better understanding of this reaction. Two different approaches have been developed in this work. They both led to total control of the regioselectivity of this cycloaddition. Cycloadditions performed by reactions using a nitrosopyridine dienophile and catalyzed by a chiral source of copper allows the synthesis of cycloadducts precursor of azaspirocycles with a modest enantioselectivity. Cycloadditions using a chloronitroso chiral dienophile derived from xylose allowed the synthesis of oxaspiraniques precursors with enantioselective excess of at least 95%. The last approach was finally validated by the synthesis of various spiroethers and spirolactones through N-O bond cleavage an intramolecular cyclizations. Finally, the vinyl triflate function of the spirolactones and spiroethers was engaged in Suzuki couplings to introduce molecular diversity at a late stage allowing the synthesis of 9 different spiranic structures including 5 enantioenriched

APA, Harvard, Vancouver, ISO, and other styles

15

Yu, Jianguo. "Novel chiral phosphonium ionic liquids as solvents and catalysts for cycloadditions : investigation of the Diels-Alder reaction of a series of dienes and dienophiles in novel chiral phosphonium ionic liquids." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4307.

Full text

Abstract:

The use of ionic liquids (ILs) as both reagents and solvents is widely recognised. ILs offer a number of advantages compared to regular molecular solvents. These advantages include: chemical and thermal stability, no measurable vapour pressure, no or lower toxicity, non-flammability, catalytic ability, high polarity and they can be recycled. There are a number of research groups investigating the various applications of this reaction medium and most studies have focused on solvents derived from the imidazolium cation. The use of the imidazolium-based ILs in the Diels-Alder reaction has been studied in detail and higher yields compared to conventional methods have been reported. The IL affects the rate and interesting selectivities have been observed. However, not much attention has been paid to the scope and limitations of phosphonium ILs (PILs). Therefore the focus of this thesis is the synthesis and application of novel chiral PILs as environmentally benign, task-specific solvents for the Diels-Alder reaction. In addition, this research seeks alternative ways to eliminate the use of toxic heavy metal catalysts and to exploit methodologies which reduce the energy consumption of the Diels-Alder reaction. A series of CILs were synthesised from the chiral pool and they were characterised by thermogravimetric analysis, differential scanning calorimetry and spectroscopy. They were then investigated as solvents and catalysts in the Diels-Alder reactions of a series of dienes (cyclopentadiene, isoprene, 2,3-dimethylbuta-1,3-diene, furan, pyrrole, N-methyl pyrrole) and dienophiles (methyl acrylate, methyl vinyl ketone, acrylonitrile, dimethyl maleate, acrolein, dimethylacetylene dicarboxylate, maleic anhydride and maleimide). Investigation of the effect of PILs in the presence of three heterogeneous catalysts Al2O3, SiO2 and K-10 montmorillonite were studied. Ultrasound and microwave-assisted Diels-Alder reactions in the PILs, in the absence and presence of the catalysts, were also studied. The reactions of these prototypical substrates illustrated that the solvents are indeed task-specific.

APA, Harvard, Vancouver, ISO, and other styles

16

Chabour, Ihssene. "1,3-Dipolar cycloadditions using catalysts with double chirality and novel multicomponent [4+2] processes." Doctoral thesis, Universidad de Alicante, 2021. http://hdl.handle.net/10045/114674.

Full text

Abstract:

In this thesis, different cycloaddition reactions, such as the enantioselective 1,3-dipolar-cycloaddition, which takes place between in situ generated stabilized azomethine ylides, and electrophilic alkenes, and the diastereoselective multicomponent reactions Amine-Aldehyde-Dienophile (AAD) or Phosphoramidate-Aldehyde-Dienophile (PAD) are described. In Chapter 1, an asymmetric 1,3-dipolar cycloaddition reaction involving an imino ester with tert-butyl acrylate was carried out using a silver(I) complex with double chirality, formed from a chiral phosphoramidite and chiral silver binolphosphate(I). The goal of this reaction is to synthesize key enantiomerically enriched structures to access the GSK-third generation of HCV inhibitors. In Chapter 2, the synthesis of polysubstituted cyclohex-2-enylamines using the multicomponent Amine-Aldehyde-Dienophile reaction involving benzyl or 4-methoxybenzylamine, is described. The study the diastereoselective version, employing commercially available chiral benzylic amines, or even a maleimide with the chiral information at the nitrogen atom, are also reported. In Chapter 3, the synthesis of polysubstituted cyclohex-2-enylamines derivatives using the multicomponent Phosphoramidate-Aldehyde-Dienophile (PAD), is described. Several series of N-substituted phosphoramidates reacted with α,β-unsaturated aldehydes, bearing hydrogen atoms at the γ-position, in good yields.

APA, Harvard, Vancouver, ISO, and other styles

17

Sultan, Nisrine. "Preparations selectives de derives du 7-oxanorborna-2,5-diene : utilisation comme formes masquées de composés acetyleniques." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112132.

Full text

Abstract:

En vue d’effectuer des préparations sélectives de composés hétérocycliques, une étude de la synthèse et de la réactivité de 7-oxanorborna-2,5-diènes portant des groupes électroattracteurs différents sur les positions 2 et 3 a été réalisée. Ces composés sont des formes masquées de composés acétyléniques dissymétriques.Dans un premier temps, nous avons optimisé une nouvelle méthode de synthèse sélective d’acétylènedicarboxylates dissymétriques par mono-transestérification d’acétylènedicarboxylates de dialkyle symétriques avec des alcools en présence de la lipase de Candida rugosa. Cette méthode nous a permis d’obtenir les diesters dissymétriques avec de bons rendements et une haute sélectivité a priori inattendue.Dans un second temps, nous avons développé des synthèses régiosélectives de dérivés de l’acide 7-oxanorborna-2,5-diène-2,3-dicarboxylique selon deux stratégies. Dans une première approche, une réaction de Diels-Alder intramoléculaire entre un furane et un composé acétylénique reliés par une agrafe siliciée a été réalisée, suivie d’une coupure des liaisons Si-C. Cette cycloaddition [4+2] s’effectue uniquement en présence de MeAlCl2 avec des rendements moyens. Dans certains cas, la coupure des liaisons Si-C conduit aux diesters désirés. Dans une deuxième approche, une mono-saponification d’oxanorbornadiène-2,3-dicarboxylates de dialkyle a permis d’accéder régiosélectivement à des monoacides et des réactions de couplage avec des amines ou des alcools ont conduit sélectivement à des dérivés présentant deux groupes électroattracteurs différents.Dans une dernière partie, nous avons effectué la préparation régiosélective de 3-pyrrolines par cycloaddition [2+3] d’un ylure d’azométhine suivie d’une réaction de rétro-Diels-Alder à partir des 7-oxanorbornadiènes comportant deux groupes électroattracteurs différents. La préparation aisée de 3-pyrrolines condensées non décrites dans la littérature a été obtenue par formation inattendue d’un motif succinimide dans le cas des amidoesters.En conclusion, il apparaît que la présence du groupe éthyle en tête de pont des 7-oxanorborna-2,5-diènes semble suffisante pour contrôler la régiosélectivité de ces cycloadditions
In order to selectively prepare heterocyclic compounds, a study of the synthesis and reactivity of 7-oxanorborna-2,5-dienes with different electron-withdrawing groups on the 2 and 3 positions was performed. These compounds are masked forms of unsymmetrical acetylenic compounds. At first, we have optimized a new method for the selective synthesis of unsymmetrical diesters by transesterification of symmetrical dialkyl acetylenedicarboxylates in the presence of Candida rugosa lipase. This unexpectedly highly selective method allowed us to obtain unsymmetrical acetylenedicarboxylates in good yields.In a second part, we have developed a regioselective synthesis of 7-oxanorborna-2,5-diene-2,3-dicarboxylic acid derivatives according to two strategies. In one approach, an intramolecular Diels-Alder reaction between a furan and an acetylenic compound connected by silicon-containing tethers was performed, followed by a cleavage of the Si-C bonds. This [4+2] cycloaddition was carried in the presence of a Lewis acid, only MeAlCl2 gave the expected product and so in moderate yields. In most cases, the cleavage of Si-C bonds leads to the desired diesters. In a second approach, a mono-saponification of dialkyl oxanorbornadiene-2,3-dicarboxylates provided access regioselectively to mono-acids and coupling reactions with amines or alcohols selectively led to poly-functionalized products containing two different electron-withdrawing groups.In the last part, we have regioselectively prepared 3-pyrrolines by [2+3] cycloaddition of an azomethine ylide to 7-oxanorbornadienes bearing electroattracting groups followed by a retro-Diels-Alder reaction. An easy synthesis of previously unknown condensed 3-pyrrolines was obtained by formation of an unexpected succinimide pattern from amidoesters. In conclusion, it appears that the presence of an ethyl group on the bridgehead carbon atom of 7-oxanorborna-2,5-dienes seems sufficient to control the regioselectivity of these cycloadditions

APA, Harvard, Vancouver, ISO, and other styles

18

Filho, Luiz Carlos da Silva. "Pentacloreto de nióbio como ácido de Lewis em reações de cicloadição [2+2] e [4+2]." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/59/59138/tde-22122006-124222/.

Full text

Abstract:

O objetivo deste trabalho foi investigar o uso de NbCl5 como ácido de Lewis em reações de cicloadição. Foram estudadas algumas reações de cicloadição [2 + 2], Reações de Diels-Alder entre enonas e ciclopentadieno e Reações da aza-Diels-Alder com bases de Schiff, avaliando o efeito da temperatura e da concentração molar do NbCl5. A comparação dos rendimentos, dos produtos formados e do tempo de reação com NbCl5, também foi um ponto fundamental da pesquisa. As reações de cicloadição [2 + 2] foram realizadas entre ésteres propiólicos e diferentes tipos de alcenos (éteres enólicos de silício e alcenos alifáticos). Nas reações com os éteres enólicos de silício não foi verificada a formação dos respectivos adutos de ciclobuteno, pois o NbCl5 promove a quebra da ligação oxigênio-silício, não levando à formação do produto desejado. Nas reações com os alcenos alifáticos foi possível obter o respectivo aduto, porém com rendimentos menores que com outros ácidos de Lewis. Quanto às reações de Diels-Alder, foram investigadas as reações entre diferentes ciclo-enonas (dienófilos de baixa reatividade) com ciclopentadieno (dieno) na presença de NbCl5. Os resultados obtidos indicam que o NbCl5 é um bom ácido de Lewis para ativar reações de Diels-Alder, apresentando tempos reacionais menores e alta diastereosseletividade a temperaturas mais baixas, quando comparado com outros ácidos de Lewis. A possibilidade de efetuar reações do Diels-Alder a -78 0C é um dos aspectos de destaque neste trabalho, pois, além de demonstrar a forte ativação do sistema enona exercido pelo NbCl5, possibilita obter produtos com alta seletividade. Paralelamente aos estudos de sistemática reacional foram realizados estudos de elucidação estrutural completa de alguns dos compostos sintetizados, utilizando-se diversas técnicas de RMN (uni e bidimensionais), e o auxílio de cálculos teóricos. Nas reações de aza-Diels-Alder entre bases de Schiff e di-hidropirano, o NbCl5 se mostrou um ótimo catalisador para a síntese de derivados de piranoquinolinas. Estes derivados formam uma importante classe de produtos naturais que apresentam ampla atividade biológica. As reações foram conduzidas com baixas concentrações de nióbio e em tempos relativamente curtos, obtendo-se rendimentos variando de 72 a 96 %. Outro fator a se destacar é a alta diastereosseletividade encontrada nestas reações. Também foram realizados estudos da atividade tripanocida dos derivados de piranoquinolinas preparados através das reações de aza-Diels-Alder catalisadas por NbCl5.
The aim of this work was to investigate the use of NbCl5 as Lewis acid in cycloadittion reactions. We have studied [2 + 2] cycloaddition reactions, Diels-Alder reactions between enonas and cyclopentadiene and aza-Diels-Alder reactions with Schiff bases. The effects of the temperature and of the molar concentration of NbCl5 were also evaluated. Comparasion of reaction yields, obtained products as well as reation time with NbCl5 were also a key point on this work. The [2 + 2] cycloaddition reactions were performed using propiolic ester and different types of alkenes (silyl enol ethers and aliphatic alkenes). In the reactions with silyl enol ethers, formation of the corresponding cyclobutene aductts was not verified, since the NbCl5 promotes the rupture of oxygen-silicon bonds, and the desired product is not obtained. In the reactions with aliphatic alkenes, it was possible to obtain the adduct, however, in lower yields as compared to those obtained with others Lewis acids. Regarding the Diels-Alder reactions, we have investigated reactions using different cycloenones (dienophiles of low reactivity) with cyclopentadiene (diene) with NbCl5. The obtained results indicate that NbCl5 is a good Lewis acid to activate these Diels-Alder reactions, resulting in shorter reaction times and higher diastereoselectivity at lower temperatures than other Lewis acids. The possibility of carrying out Diels-Alder reaction at -78 0C is another remarkable aspect of this work. Besides demonstrating the strong activation of the enone system by NbCl5, it opens the possibility of obtaining high stereoselectivity. We have also performed studies of complete structural elucidation of some compounds by using different NMR techniques (uni and bidimensional), with the help of theoretical calculations. In the aza-Diels-Alder reactions between Schiff bases and dihydropyran, the NbCl5 was an excellent catalyst for the synthesis of pyranoquinoline derivatives. These derivatives are an importante class of natural products that exhibit wide range of biological activity. The reactions were carried out at low concentration of niobium and in relatively short times, resulting in yields varying from 72 to 96 %. Another aspect that should be remarked is the high diastereoselectivity found in these reactions. We have also carried out studies of tripanocydal activity of pyranoquinoline derivatives prepared through aza-Diels-Alder reactions catalyzed by NbCl5.

APA, Harvard, Vancouver, ISO, and other styles

19

Duflos, Jack. "Synthèse et réactions de cycloadditions sur des systèmes pyrroliques à noyaux condensés." Rouen, 1987. http://www.theses.fr/1987ROUES003.

Full text

Abstract:

Synthèse à partir d'o-diformyl N-méthyl pyrroles; additions de Diels-Alder avec le N-phényl maléimide et le butynedioate de diméthyle de benzo dipyrroles, pyrrolo phtalazines, cyclohepta (C) pyrrolones-6 et pyrrolo pyridines

APA, Harvard, Vancouver, ISO, and other styles

20

Ferroud, Clotilde. "Étude de la réaction de Diels-Adler intra et intermoléculaire sous haute pression : application à la synthèse stéréosélective d'alcaloïdes de l'indole du groupe des yohimbanes." Paris 6, 1986. http://www.theses.fr/1986PA066023.

Full text

Abstract:

Le schéma de synthèse repose sur une unité bicyclique, précurseur direct des unités (d,e) du squelette pentacyclique. Cet intermédiaire est basé sur une réaction de Diels-Alder sous haute pression, utilisant la cycloaddition de diènes de structure donneur-accepteur 1,4 avec une lactone insaturée comme diénophile. La synthèse du système pentacyclique est exposée à partir de cet intermédiaire clé.

APA, Harvard, Vancouver, ISO, and other styles

21

(14010168), Mirta Golic. "The preparation of dienes and dienophiles containing nucleic acid bases." Thesis, 1999. https://figshare.com/articles/thesis/The_preparation_of_dienes_and_dienophiles_containing_nucleic_acid_bases/21397758.

Full text

Abstract:

The work presented in this thesis deals initially with the synthesis of rigid polyalicyclic dienes and dienophiles with pyrimidine moieties inbuilt in a rigid fashion (building BLOCKS). This work has allowed the production of a new class of ribbon molecules with precisely defined size, shape and position of the pyrimidine ring. In the second stage of the project, an assessment of their ability to participate in cycloaddition reactions as pyrimidine building BLOCK* components was investigated.

2,4-Dimethoxy-1,3-diazaanthracene (I) has acted as the pyrimidine transfer reagent for preparing building BLOCKs. The Diels-Alder adducts IV and V (Scheme I), prepared by reaction of I with norbomadiene, are new pyrimidine dienophilic BLOCKs. Both I and 2,4-dichloro-1,3-diazaanthracene (II) were active in photochemical [4π+4π] cycloaddition reactions with cyclopentadiene to form a second class of building BLOCKs VII and VIII (Scheme I). In addition, the photodimerisation of I and II was studied and structures IX-XII assigned on the basis of spectral and X-ray method.

The 2,4-dichloro-photoadduct VIII is of particular importance for this work since it is easily hydrolysed (2M NaOH, 60 °C, overnight) to the corresponding uracil XIII In contrast, thermal adducts IV and V were very difficult to hydrolyse (NaOH fusion) to uracils XIV and XV (Figure I).

The availability of pyrimidine BLOCKs which contain a reactive π-bond, e.g. (IV, V, VII and VIII) has enabled us to employ 3,6-di(2'-pyridyl)-s-tetrazine (XVI) and ACE (Alkene plus Cyclobutene Epoxide) coupling methods to obtain precisely functionalised ribbon molecules in a direct, convergent synthetic strategy.

The synthesis of the bis-pyrimidines by coupling norbornene reagents using 3,6-di(2'-pyridyl)-s-tetrazine is illustrated in Scheme II. In the first step, s-tetrazine XVI was reacted with pyrimidine BLOCK V under basic conditions to generate the dihydropyridazine XVII. This diaza-1,3-diene was reacted with a further equivalent of V under high pressure conditions to yield the bis-pyrimidines XVIII and XIX, which were separated by radial chromatography. The same procedure was used to link pyrimiclines to other effectors by using alternative alkenes in the second step.

The ACE coupling protocol is illustrated by the reaction of alkene VIII with the dimethoxynaphthalene-containing epoxide XX (Scheme III). The reaction can be conducted under thermal or photochemical conditions and is considered to proceed via 1,3-dipolar intermediate formed by ring-opening of the epoxide C-C bond of XX (See Chapter 4).

Each class of coupled adduct could be hydrolysed to the corresponding uracil by using either acid (XXII) or base (XXIII) hydrolysis conditions, the choice depending on the structure of the molecule in question and its substituents.

The work presented in this thesis involves a deal of new work and has been instrumental in the development of the Lego^®-based BLOCK assembly protocol for ribbon molecules construction.

APA, Harvard, Vancouver, ISO, and other styles

22

Lording, William James. "A deeper understanding of the Diels–Alder reaction." Phd thesis, 2010. http://hdl.handle.net/1885/11776.

Full text

Abstract:

The Diels-Alder reaction was discovered in 1928 and has become the most efficient and practical method for the synthesis of six-membered carbocyclic and heterocyclic rings. This thesis comprises three chapters of results and discussion with the Diels-Alder reaction as a theme. Chapter 2 details an investigation of endo:exo selectivity in the Diels-Alder reactions of 1,3-butadiene. Chapter 3 explores aspects of the intramolecular Diels-Alder reactions of some substituted 1,3,8-nonatrienes, and Chapter 4 describes the domino Diels-Alder reactions of 1,4-diiodo-1,3-butadiene. The Diels-Alder reaction is powerful, general, and widely used in chemical synthesis, and it is well known that many Diels-Alder reactions exhibit endo selectivity, in accord with Alder’s empirical rule. The origins of endo:exo selectivity in the Diels-Alder reaction, however, are not completely understood and there is a dearth of experimental evidence concerning the Diels-Alder reactions of the archetypal 1,3-diene, 1,3- butadiene. Chapter 2 describes a study of the Diels-Alder reactions of an isotopically labelled 1,3-butadiene with a range of simple dienophiles, allowing the endo:exo selectivities of these important reactions to be determined for the first time. The experimental data shed light on the origins of endo:exo selectivity in the Diels-Alder reaction and will serve as an important reference for future computational investigations in this area. The intramolecular Diels-Alder reaction shares many of the virtues of its intermolecular counterpart, however its use in chemical synthesis is limited because intramolecular Diels-Alder reactivity and stereoselectivity are often governed by subtle factors, and can be very difficult to predict. As part of a comprehensive experimental and computational collaboration, Chapter 3 describes an investigation of the heat and Lewis acid promoted intramolecular Diels-Alder reactions of some ether tethered 1,3,8-nonatrienes. Also presented are the results of a rate study and a kinetic isotope effect study involving the intramolecular Diels-Alder reactions of some 1,3,8-nonatrienes. The experimental data are analysed and compared with predicted stereoselectivities, activation barriers and kinetic isotope effects obtained from computational modelling. Increased efficiency in chemical synthesis conserves resources, reduces waste, and saves time and money. Domino reactions are particularly efficient processes, which can generate complex products from simple reactants. Chapter 4 describes an investigation of the domino Diels-Alder reactions of (1E,3E)-1,4-diiodo-1,3-butadiene with maleimide dienophiles, through which a family of bicyclo[2.2.2]oct-2-ene derivatives are produced in one high yielding and stereoselective synthetic step.

APA, Harvard, Vancouver, ISO, and other styles

23

Chen, Shang-Hong, and 陳尚鴻. "1. Approach to the kempane skeleton via intramolecular Diels-Alder cycloaddition of fulvene 2. Application of organocatalysts in Baylis-Hillman reaction and related cycloaddition." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/51860899827903256040.

Full text

Abstract:

博士
國立中正大學
化學所
94
Part 1: Approach to the kempane skeleton via intramolecular Diels-Alder cycloaddition of fulvene The Kempane skeletons can be prepared rapidly via intramolecular Diels-Alder cycloadditions (IMDA) of fulvenes. The chemistry upon both intramolecular Diels-Alder cycloadditions and Prins reaction. Part 2: Application of organocatalysts in Baylis-Hillman reaction and related cycloaddition A highly enantioselective proline catalyzed intramolecular Baylis–Hillman reaction of hept-2-enedial is reported. Addition of imidazole to the mixture results in an unusual inversion of enantioselectivity. The organocatalyzed [3 + 3] and [4+2] cycloaddition of ?β-unsaturated aldehydes affored aromatic aldehydes.

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Diels-Alder cycloaddition reactions'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles