Oxabicyclic alkenes have been the focus of many synthetic studies as they are versatile compounds which act as synthetic intermediates to produce a variety of useful heterocyclic, carbocyclic and acyclic products. The nucleophilic ring opening reaction of oxabenzonorbornadiene was studied. Methanol was the primary nucleophile used throughout the investigation, however various other alcohol nucleophiles were also tested for their efficacy. The effects of substitution were explored, providing ring opened products in yields of up to 81%. The [2+2] cyclodimerization reaction of oxanorbornadienes was also examined providing the first examples of dimers of this kind. The scope was expanded to include other 2,3-diester oxanorbornadienes as well as various C1 substitutions. Changing the ester moiety did not affect the reaction, however the addition of a C1 alkyl substituent did result in lower yields. Moderate yields of up to 66% were obtained. Additionally, a new ruthenium complex was discovered in the process.

This report is an investigation of regioselectivity in transition metal catalyzed ring-opening reactions involving unsymmetrical oxabicycles, specifically with a substituent at the C1 position. This report also provides the details of the work conducted towards the preparation of various oxanorbornadienes and their precursors. A large number of reactions have been developed using various transition metal catalysts on oxabicyclic alkenes to form functionalized organic scaffolds. However, most of the literature is limited to symmetrical substrates. Introduction of a substituent at the bridgehead carbon of the bicyclic ring makes the molecule unsymmetrical. The implications of loss of the plane of symmetry in C1 substituted oxabicyclic ring are manifested in interesting ways during various metal catalyzed reactions. The fundamental basis for the current work is to study the consequences of transition metal catalyzed ring opening reactions of unsymmetrical bicyclic alkenes. The reactivity of a wide range of C1 substituted benzoxanorbornadienes and oxanorbornadienes in palladium and nickel-catalyzed ring opening reactions was explored. The palladium catalyzed ring opening reaction of both electron rich and electron deficient C1 substituted benzoxanorbornadienes are optimized. The ring opening reactions with electron withdrawing C1 substituent resulted in formation of substituted naphthalene-1-carboxylic acid methyl ester derivatives in up to 85% yield. Electron donating substituents on the C1 position of benzoxanorbornadiene led to the formation of substituted cis-1,2-dihydronaphthol rings in excellent yields. Palladium catalyzed ring opening reactions were also explored with a wide range of aryl iodides and halobenzenes. The electronic and steric effects of the substituent at the C1 position of oxabicyles were also investigated. The nickel catalyzed ring opening reactions resulted in formation of inseparable regioisomeric mixtures of products. However, it was found that the nickel catalyzed ring opening of 1-methoxycarbonyl-7-oxabenzonorbornadiene occurred regioselectively affording a single product. A scalable procedure for preparation of large quantities of 2-bromofuran was developed. 2-Aryl furans were prepared using Suzuki cross coupling protocols of 2-bromofuran with aryl boronic acids whereas 2-alkyl furans were prepared by iron catalyzed cross coupling reaction of 2-bromofuran with various alkyl and cycloalkyl Grignard reagents. The 2-substituted furans were used for the preparation of novel C1 substituted benzoxanorbornadiene and oxanorbornadienes.

Les tétrazoles ont une place importante dans la chimie médicinale contemporaine par leurs caractéristiques spatiales et électroniques uniques. Leur haute teneur en azote leur confère également des qualités requises dans le développement de substances explosives et de haute énergie. Le développement de nouveaux outils synthétiques pour les créer prend donc ici tout son sens. Dans cet ouvrage, il est tout d’abord question d’une nouvelle méthode de synthèse qui génère des tétrazoles bicycliques en conditions douces par l’entremise d’azidonitriles aliphatiques séparés par trois ou quatre atomes de carbone (effet de proximité) et d’acides de Lewis. De plus, cette méthode de synthèse présente une réaction tandem qui génère des tétrazoles oxabicycliques 1,5-dialkylés via une cycloaddition 1,3-dipolaire diastéréosélective à partir d’azidoacétals ou d’azidocétals arborant un azoture proximal. La réaction s’effectue dans le nitrométhane de 0 °C à la température ambiante avec du TMSCN et est promue par une variété d’acides de Lewis dont le BF3OEt2. Les aspects mécanistiques de la réaction (l’ouverture des acétals, l’équilibre entre les éthers de cyanhydrine, la cycloaddition 1,3-dipolaire diastéréosélective et le réarrangement de Boyer-Schmidt-Aubé) ainsi que les paramètres réactionnels (solvants, acides de Lewis, stœchiométrie, sources de cyanure, etc.) seront en outre abordés. Ensuite, le motif de tétrazole oxabicyclique a été l’objet de diversifications, de fonctionnalisations et de transformations afin d’en valoriser l’utilité. Des réactions d’alkylations, d’azoturations radicalaires, de bêta-éliminations et de diversifications de la chaîne latérale ont été étudiées. De ces mêmes motifs de tétrazoles, la synthèse de tétrazoles azabicycliques et celle de morpholines 2,6-polysubstituées ont aussi été investiguées. La synthèse d’un sel de tétrazolium et l’alkylation de 5-tétrazolyllithiums ont aussi fait l’objet d’études préliminaires. Enfin, une étude théorique en DFT a été effectuée pour mieux comprendre l’équilibre tétrazole-azidoazométhine sur des motifs de types benzo- et pyrido- diazidodiazines parents à la 6-azidotétrazolo[5,1-a]phthalazine, un métabolite toxique du Gymnodinium breve (Ptychodiscus brevis, aussi actuellement connu sous le nom de Karenia brevis). Les aspects thermodynamiques, les états de transition, les orbitales HOMO, les cartes de potentiels d’ionisation locaux, les cartes de densité de la LUMO, les effets de solvant et certains paramètres permettant d’évaluer l’aromaticité (indices de Bird, ordres de liaison minimaux de Jug, indices HOMA et NICS) ont été considérés dans l’étude. Le constat a été que certaines des analyses théoriques peuvent constituer de bons outils prédictifs, particulièrement avec des considérations thermodynamiques, mais que cette approche a aussi ses limites qui sont principalement dues aux incertitudes inhérentes aux calculs théoriques. / Tetrazoles have an important place in contemporary medicinal chemistry due to their unique spatial and electronic characteristics. Their high nitrogen content also gives them the qualities required for the development of explosive and high energy substances. The development of new synthetic tools to create them takes here all its meaning. Therefore, in this work, a new synthesis method that generates bicyclic tetrazoles under mild conditions using aliphatic azidonitriles separated by three or four carbon atoms (proximity effect) and Lewis acids will first be discussed. In addition, a tandem reaction which generates 1,5-dialkylated oxabicyclic tetrazoles via a diastereoselective 1,3-dipolar cycloaddition from azidoacetals or azidoketals bearing a proximal azide will also be disclosed. The reaction is carried out in nitromethane at 0 °C to room temperature with TMSCN and is promoted by a variety of Lewis acids including BF3OEt2. The mechanistic aspects of the reaction (acetal opening, equilibrium between cyanohydrin ethers, diastereoselective 1,3-dipolar cycloaddition and Boyer-Schmidt-Aubé rearrangement) as well as the reaction parameters (solvents, Lewis acids, stoichiometry, cyanide sources, etc.) will be discussed. Furthermore, the oxabicyclic tetrazole unit was involved in diversifications, functionalizations and transformations to enhance its utility. Reactions of alkylations, radical azidations, beta-eliminations and diversifications of the side chain were applied. From these same tetrazole units, the synthesis of azabicyclic tetrazoles and that of 2,6-polysubstituted morpholines was also investigated. The synthesis of a tetrazolium salt and the alkylation of 5 tetrazolyllithiums were also the subject of preliminary studies. Finally, a theoretical DFT study was carried out to have a better understanding of the tetrazole-azidoazomethine equilibrium on benzo- and pyrido- diazidodiazines similar to 6 azidotetrazolo [5,1-a] phthalazine, a toxic metabolite from Gymnodinium breve (Ptychodiscus brevis, actually known as Karenia brevis). Thermodynamic aspects, transition states, HOMO orbitals, local ionization potential maps, LUMO density maps, solvent effects, and some parameters to evaluate the aromaticity (Bird index, Jug minimum bond order, HOMA index and NICS) were considered in the study. It has been noted that some of the theoretical analysis can be good predictive tools, particularly with thermodynamic considerations, but they also have their limits, which are mainly due to the uncertainties inherent in the theoretical calculations.