Cyclopropanes are strained molecules and undergo reactions, for example, through ring opening and rearrangements. Preparative methods and reactivities of cyclopropanes are known widely in organic synthesis. The high reactivities inherent in cyclopropanes allow them to be valuable building blocks in organic synthesis. The combination of cyclopropanes and carbohydrates has been explored in recent years. Carbohydrates, the naturally-occurring members of chiral pool, are attractive platforms for asymmetric synthesis. Cyclopropanation of, for example, unsaturated sugars affords [4.1.0] bicyclic systems, thereby combining the high reactivities of cyclopropanes together with optical purities of sugars. Chapter 1 of the Thesis describes (i) various types of cyclopropane ring opening reactions in general and (ii) known reactions of cyclopropanes in carbohydrates relevant to the work presented in the Thesis. Seven-membered cyclic sugars, namely, septanoses and septanosides, are less commonly known sugar homologues. Synthesis of septanoses arise interest, due to their configurational and conformational features and the attendant possibilities to explore their chemical, physical and biological properties. In a programme, it was desired to identify a new methodology for synthesis of septanosides. It was envisaged that 2-hydroxy glycals, namely, oxyglycals, would form as suitable substrates for ring expansion, leading to the formation of septanoside derivatives that are retained with hydroxyl groups in each carbon of the septanoside. In the event, a new methodology was identified. A carbene insertion of an oxyglycal substrate, nucleophilic ring opening of the cyclopropyl moiety, oxidation and reduction reactions were identified to expand the six membered pyranoses to seven membered septanosides (Scheme 1). The methodology was established through preparation of two configurationally different septanosides, namely, the methyl α-D-glycero-D-talo-septanoside and methyl α-D-glycero-L-altro-septanoside from D-glucose and D-galactose, respectively. Chapter 2 presents details of the methodology and the preparation of septanosides from precursors oxyglucal and oxygalactal. Scheme 1 Continuing the efforts to extend the methodology, preparation of a variety of septanosides, using phenoxides, sugars and azide were undertaken. It was found that ring opening with sugars were highly stereoselective, leading to an exclusive formation of the -anomer of sugar oxepines, whereas, the phenoxides and azide led to a mixture of anomers of the corresponding oxepines, in a ~1:1 ratio (Scheme 2). Scheme 2 An important observation was -anomer of the oxepine derived intermediates, having diketo-functionalities, underwent NaBH4 mediated conversion to diols with higher diastereoselectivities at the newly generated stereo-centers, whereas the -anomers lacked to retain the diastereoselectivities, in the case of aryl septanosides. This part of work consolidated further the generality of the oxyglycal ring-expansion method to prepare septanosides, possessing different substituents at their reducing ends. Chapter 3 describes the details of syntheses and characterization of various aryl septanosides, septanoside disaccharides and azido-septanoside derivatives. It was planned further to synthesize septanoside containing di-and trisaccharides from naturally-occurring disaccharides, through the oxyglycal route. Oxyglycals, derived from lactose and maltose, were expanded to septanoside-containing trisaccharides through a ring expansion method. Thus septanosides incorporated disaccharides and trisaccharides, with 6-7, 6-7-5 and 6-7-6 ring sizes, were prepared through the ring expansion method. The reaction not only led to a ring expansion, but also, to a concomitant glycoside formation, in a stereoselective manner (Scheme 3). Scheme 3 A conformational analysis of the galacto-septano-glucopyrano-configured 6-7-6 trisaccharide was undertaken with aid of NMR spectroscopy and computational methods. Spatial distances from NMR experiments were utilized while performing molecular dynamics with AMBER* force field and further optimizations using B3LYP/6-31+G* level. The study showed that septanoside ring in the trisaccharide adopted twist-chair conformation O,1TC5,6, as shown in Figure 1. Chapter 4 describes synthesis of septanoside containing di-and trisaccharides and conformational analysis of a 6-7-6 trisaccharide, through solution phase and computational methods. An effort was pursued to prepare septanoside-based amphiphiles with varying alkyl chain lengths, using our newly established methodology and to study their amphiphilicities. A series of septanoside amphiphiles, having C10 to C18 alkyl groups, were prepared as their -anomers as shown in Figure 2. The amphiphilic behavior of the alkyl septanosides was assessed through studies of their liquid crystalline (LC) properties. The LC properties were evaluated using polarizing optical microscopy, differential scanning calorimetry and powder X-ray diffraction methods. All the septanoside amphiphiles exhibited a smectic A phase in general. DSC thermograms showed crystal-crystal and crystal-mesophase phase transitions. Powder X-ray diffraction studies allowed to identify the lamellar structuring of the smectic A phase. Further, two distinct two layer spacings were observed. Such an observation is un-usual in carbohydrate liquid crystals. Chapter 5 details of synthesis and studies of the mesomorphic behavior of septanoside amphiphiles. In summary, the Thesis establishes a new route to synthesize septanoside derivatives, from oxyglycal sugar derivatives. Ring expansion of a pyranoside to a septanoside was achieved through key reactions of a cyclopropanation, ring opening, oxidation and reduction. Methyl α-D-glycero-septanoside derivatives were synthesized, from the corresponding oxyglycals. Cyclopropane ring opening ability of various nucleophiles were studied, it was found that ring-opening reactions with phenols, sugars, and azides are effective, which facilitated the synthesis of various aryl, glycosyl and azido-substituted septanosides. Synthesis of septanosides incorporated with di-and trisaccharides were accomplished. The detailed conformational analysis studies showed that the septanoside adopted twist-chair conformation in a trisaccharide molecule. Preparation and studies of septanoside based amphiphiles and their mesophase behavior were also accomplished. Overall, the studies presented in the Thesis provide a new insight to ring expanded sugars. The salient features of the present method are that the intermediates such as the seven membered vinyl halides, vinyl ethers, the diketones and the diols are potential sites for many other functionalizations. These features can be explored further in functionalizing the newly formed septanosides. (For structural formula pl see the pdf file)

This thesis describes the synthesis of novel ligands that include enantiomerically pure acetal and oxazoline moieties. These ligands are utilised in a number of metalmediated asymmetric syntheses. All asymmetric acetals and pyridine based acetals are synthesised in good yield in a single step from their corresponding enantiomerically pure diols. C2 symmetric bisacetals are investigated as ligands in the organolithium and Grignard additions to benzaldehyde with promising results. C2 symmetric bisacetals and pyridine based acetals are tested for their ability to induce asymmetry in copper(l) catalysed cyclopropanation of styrene using ethyl diazoacetate and the lanthanide(lII) catalysed Diels-Alder cycloaddition involving Danishefsky's diene with little success. Enantiomerically pure phosphinooxazoline ligands are available in good yield in two steps from their corresponding enantiomerically pure aminoalcohols. Enantiomerically pure acetal substituted pyridines and phosphinooxazoline ligands are considered in the rhodium (I) catalysed hydrosilylation of ketones. Reaction conditions for the more successful phosphinooxazoline ligands are optimised. Using these ligands a range of enantiomerically enriched alcohols is presented in good yield and enantiomeric excess. Novel phosphinooxazoline ligands are applied to the palladium(O) catalysed allylic substitution reaction with excellent enantioselectivities of the substitution product.

Ce mémoire présente trois approches différentes vers la synthèse du 3–(trans–2–nitrocyclopropyl)alanine, un intermédiaire synthétique de la hormaomycine. Cette molécule naturelle démontre d’intéressantes activités biologiques et pharmacologiques. Il est intéressant de souligner que ce dérivé donne facilement accès au 3–(trans–2–aminocyclopropyl)alanine, unité centrale de la bélactosine A. Ce composé naturel possédant lui aussi d’intéressantes propriétés biologiques, plusieurs études relationnelles structures-activités menant à des dérivés plus actifs de cette molécule ont été entreprises, démontrant l’intérêt toujours présent de synthétiser de façon efficace et optimale ces dérivés cyclopropaniques. Une méthodologie développée au sein de notre groupe de recherche et basée sur une réaction de cyclopropanation intramoléculaire diastéréosélective sera mise à profit afin d’élaborer une nouvelle voie de synthèse aussi élégante qu’efficace à la construction du 3–(trans–2–nitrocyclopropyl) alanine. En utilisant un carbène de rhodium généré soit par la dégradation d’un dérivé diazoïque, soit par la formation d’un réactif de type ylure d’iodonium, une réaction de cyclopropanation diastéréosélective permettra la formation de deux autres centres contigus et ce, sans même utiliser d’auxiliaire ou de catalyseur énantioenrichis. Ensuite, un réarrangement intramoléculaire précédant deux réactions synchronisées d’ouverture de cycle et de décarboxylation permettront l’obtention du composé d’intérêt avec un rendement global convenable et en relativement peu d’étapes. De cette manière, la synthèse formelle de la bélactosine A et de l’hormaomycine a été effectuée. Cette synthèse se démarque des autres par l’utilisation d’une seule transformation catalytique énantiosélective. / This master’s thesis presents three different approaches toward the synthesis of 3–(trans–2–nitrocyclopropyl)alanine, a key constituent of the natural product hormaomycin. This unusual compound demonstrates interesting biological and pharmaceutical activity. It is noteworthy that this unique amino acid can be readily converted to the corresponding 3–(trans–2–aminocyclopropyl)alanine, the central core of belactosin A, a natural compound exhibiting interesting biological properties. Efficient syntheses of these aminocyclopropane derivatives are of current interest since several structure-activity relationships in syntheses of belactosin A and hormaomycin analogues are currently under study in an effort to discover enhanced biological activity. A methodology developed in our research group based on a diastereoselective intramolecular cyclopropanation reaction will be used to elaborate a unique and elegant pathway to the synthesis of the 3–(trans–2–nitrocyclopropyl)alanine. By using a rhodium carbene generated either by the degradation of a diazoic derivative or by the formation of the corresponding iodonium ylide, a diastereoselective cyclopropanation reaction can be applied in the concerted elaboration of two chiral centers needed in the desired aminocyclopropanes, avoiding in this way the utilisation of chiral reagents. Following this key sequence, an intramolecular rearrangement followed by synchronous ring–opening/decarboxylation reactions will permit a convenient formation of the desired product in an acceptable overall yield and in few ensuing steps. In this manner, the formal synthesis of the hormaomycin and the belactosin A can be achieved. This synthesis is unique since it involves only one asymmetric step in the whole synthetic process.

Ce mémoire présente trois approches différentes vers la synthèse du 3–(trans–2–nitrocyclopropyl)alanine, un intermédiaire synthétique de la hormaomycine. Cette molécule naturelle démontre d’intéressantes activités biologiques et pharmacologiques. Il est intéressant de souligner que ce dérivé donne facilement accès au 3–(trans–2–aminocyclopropyl)alanine, unité centrale de la bélactosine A. Ce composé naturel possédant lui aussi d’intéressantes propriétés biologiques, plusieurs études relationnelles structures-activités menant à des dérivés plus actifs de cette molécule ont été entreprises, démontrant l’intérêt toujours présent de synthétiser de façon efficace et optimale ces dérivés cyclopropaniques. Une méthodologie développée au sein de notre groupe de recherche et basée sur une réaction de cyclopropanation intramoléculaire diastéréosélective sera mise à profit afin d’élaborer une nouvelle voie de synthèse aussi élégante qu’efficace à la construction du 3–(trans–2–nitrocyclopropyl) alanine. En utilisant un carbène de rhodium généré soit par la dégradation d’un dérivé diazoïque, soit par la formation d’un réactif de type ylure d’iodonium, une réaction de cyclopropanation diastéréosélective permettra la formation de deux autres centres contigus et ce, sans même utiliser d’auxiliaire ou de catalyseur énantioenrichis. Ensuite, un réarrangement intramoléculaire précédant deux réactions synchronisées d’ouverture de cycle et de décarboxylation permettront l’obtention du composé d’intérêt avec un rendement global convenable et en relativement peu d’étapes. De cette manière, la synthèse formelle de la bélactosine A et de l’hormaomycine a été effectuée. Cette synthèse se démarque des autres par l’utilisation d’une seule transformation catalytique énantiosélective. / This master’s thesis presents three different approaches toward the synthesis of 3–(trans–2–nitrocyclopropyl)alanine, a key constituent of the natural product hormaomycin. This unusual compound demonstrates interesting biological and pharmaceutical activity. It is noteworthy that this unique amino acid can be readily converted to the corresponding 3–(trans–2–aminocyclopropyl)alanine, the central core of belactosin A, a natural compound exhibiting interesting biological properties. Efficient syntheses of these aminocyclopropane derivatives are of current interest since several structure-activity relationships in syntheses of belactosin A and hormaomycin analogues are currently under study in an effort to discover enhanced biological activity. A methodology developed in our research group based on a diastereoselective intramolecular cyclopropanation reaction will be used to elaborate a unique and elegant pathway to the synthesis of the 3–(trans–2–nitrocyclopropyl)alanine. By using a rhodium carbene generated either by the degradation of a diazoic derivative or by the formation of the corresponding iodonium ylide, a diastereoselective cyclopropanation reaction can be applied in the concerted elaboration of two chiral centers needed in the desired aminocyclopropanes, avoiding in this way the utilisation of chiral reagents. Following this key sequence, an intramolecular rearrangement followed by synchronous ring–opening/decarboxylation reactions will permit a convenient formation of the desired product in an acceptable overall yield and in few ensuing steps. In this manner, the formal synthesis of the hormaomycin and the belactosin A can be achieved. This synthesis is unique since it involves only one asymmetric step in the whole synthetic process.

No description available.

Investigation of the catalytic formation, reactivity and synthetic scope of sp³-gem-organodimetallic palladio(II)/main group metal (main group metal = tributylstannyl, dialkylalumino) alkane species has been carried out. Insight was expanded regarding the inter- and intramolecular reactivity of vinylmetallic reagents in presence of transition metal catalysts. New Pd-catalysed methodologies for carbon-carbon bond formation were developed, such as cyclopropanation of strained olefins, as well as tandem vinylalane arylation/1,2-methyl transfer and 1,2-diarylation. On the one hand, geminal π-allylpalladio(II)/tributylstannylalkane intermediates are produced by oxidative addition of Pd(0) catalysts to α-tributylstannylpropenyl acetate derivatives. They adopt ambiphilic behaviour depending on the transition metal pre-catalyst, presence or absence of phosphine ligands, and reaction temperature. In presence of tetrakis(triphenylphosphine)palladium(0) with additional bidentate ligand, the carbenoid reactivity of these gem-organobismetallic species is exposed by reaction with dimethyl malonate. Deuterium-labeling studies demonstrated sequential functionalisation of the C-Sn and C-Pd bonds. Conversely, phosphine-free catalyst bis(dibenzylideneacetone)palladium(0) uncovers metal-carbene reactivity, and dimerisation and strained alkene cyclopropanation reactions are observed. The nature of the palladium catalyst controls the reactivity of the carbenoid species. Finally, bis(cyclooctadienerhodium(I) chloride) catalytically activates the alkenylstannane moiety, leaving the allylic acetate leaving group available for further transformations. On the other hand, gem-disubstituted trifluoromethanesulfonyloxy- and iodopalladio(II)/ dialkylaluminoneopentane species are generated by intramolecular migratory insertion of 2,2-disubstituted-1-butenyldialkylalanes with σ-arylpalladium(II) triflate and iodide intermediates. Using excess Lewis-basic 1,4-diazabicyclo[2.2.2]octane, electron-rich tris(para-methoxyphenyl)phosphine ligand and acetonitrile as solvent, tandem arylation/1,2-alkyl migration from aluminum to carbon affords 7-substituted-1-ethyl-1-methylindanes containing an all-carbon quaternary stereogenic centre in good yields. This reaction is tolerant of 6-aryl methyl ethers, thioethers and trimethylsilanes. Deuterium labeling established that protiodealumination of the key neopentyl(methyl)aluminum triflate intermediate is caused by the acetonitrile solvent. The organodimetallic species in that study were shown to be configurationally stable, hence the stereospecificity of the process that proceeds via carbopalladation, transmetalation and reductive elimination of an alkylpalladium(II) intermediate. When applied to 1-naphthyl triflate-tethered vinylalanes, the same reaction conditions mediate stereospecific 1,2-diarylation, leading to 2,3,3a,4-tetrahydro-1H-cyclopenta[def]phenanthrenes in excellent yields. The influence of DABCO, tether length and solvent polarity was studied. Selective tandem arylation/1,2-methyl migration could also be achieved in non-polar solvent in absence of Lewis base. While steric properties took precedence over electronic considerations when inducing product selection, preagostic C-H···Pd interactions were postulated to facilitate 1,3-metal migration in the production of 1H-cyclopenta[def]phenanthrene derivatives.

Investigation of the catalytic formation, reactivity and synthetic scope of sp³-gem-organodimetallic palladio(II)/main group metal (main group metal = tributylstannyl, dialkylalumino) alkane species has been carried out. Insight was expanded regarding the inter- and intramolecular reactivity of vinylmetallic reagents in presence of transition metal catalysts. New Pd-catalysed methodologies for carbon-carbon bond formation were developed, such as cyclopropanation of strained olefins, as well as tandem vinylalane arylation/1,2-methyl transfer and 1,2-diarylation. On the one hand, geminal π-allylpalladio(II)/tributylstannylalkane intermediates are produced by oxidative addition of Pd(0) catalysts to α-tributylstannylpropenyl acetate derivatives. They adopt ambiphilic behaviour depending on the transition metal pre-catalyst, presence or absence of phosphine ligands, and reaction temperature. In presence of tetrakis(triphenylphosphine)palladium(0) with additional bidentate ligand, the carbenoid reactivity of these gem-organobismetallic species is exposed by reaction with dimethyl malonate. Deuterium-labeling studies demonstrated sequential functionalisation of the C-Sn and C-Pd bonds. Conversely, phosphine-free catalyst bis(dibenzylideneacetone)palladium(0) uncovers metal-carbene reactivity, and dimerisation and strained alkene cyclopropanation reactions are observed. The nature of the palladium catalyst controls the reactivity of the carbenoid species. Finally, bis(cyclooctadienerhodium(I) chloride) catalytically activates the alkenylstannane moiety, leaving the allylic acetate leaving group available for further transformations. On the other hand, gem-disubstituted trifluoromethanesulfonyloxy- and iodopalladio(II)/ dialkylaluminoneopentane species are generated by intramolecular migratory insertion of 2,2-disubstituted-1-butenyldialkylalanes with σ-arylpalladium(II) triflate and iodide intermediates. Using excess Lewis-basic 1,4-diazabicyclo[2.2.2]octane, electron-rich tris(para-methoxyphenyl)phosphine ligand and acetonitrile as solvent, tandem arylation/1,2-alkyl migration from aluminum to carbon affords 7-substituted-1-ethyl-1-methylindanes containing an all-carbon quaternary stereogenic centre in good yields. This reaction is tolerant of 6-aryl methyl ethers, thioethers and trimethylsilanes. Deuterium labeling established that protiodealumination of the key neopentyl(methyl)aluminum triflate intermediate is caused by the acetonitrile solvent. The organodimetallic species in that study were shown to be configurationally stable, hence the stereospecificity of the process that proceeds via carbopalladation, transmetalation and reductive elimination of an alkylpalladium(II) intermediate. When applied to 1-naphthyl triflate-tethered vinylalanes, the same reaction conditions mediate stereospecific 1,2-diarylation, leading to 2,3,3a,4-tetrahydro-1H-cyclopenta[def]phenanthrenes in excellent yields. The influence of DABCO, tether length and solvent polarity was studied. Selective tandem arylation/1,2-methyl migration could also be achieved in non-polar solvent in absence of Lewis base. While steric properties took precedence over electronic considerations when inducing product selection, preagostic C-H···Pd interactions were postulated to facilitate 1,3-metal migration in the production of 1H-cyclopenta[def]phenanthrene derivatives.

The homoaldol reaction is one of the most powerful methods for the construction of C–C bonds as well as 1,4-oxygenated compounds yet this reaction remains in challenging tasks due to the instability of homoenolates which spontaneously cyclize to the cyclopropanolate. A regioselective catalytic homoaldol equivalent reaction of 3-bromo vinyl acetate with aldehydes under Cr(III)-Mn(0) redox condition was developed. This homoaldol equivalent reaction allows access to the 1,4-oxygenated compounds that are not possible by a conventional aldol process. Mild hydrolysis of the vinyl acetate and reduction of the homoaldol adducts generated diols and lactols in high yield (99%). Further manipulation including stereoselective epoxidation and cyclopropanation was achieved in an efficient manner. Furans, found in many natural products and utilized in drug discovery, have been well studied but current synthetic methods toward furans have some limitations in functional group tolerance, substrate scope, and low product yield in many cases. A highly efficient and catalytic cycloisomerization reaction that transforms acetylenic α,β-epoxides to 2,3,5-tri-substituted furans under InCl3 catalysis was developed. This reaction sequence allows access to rapid construction of highly valuable, tri-substituted furan derivatives. Cross-coupling reactions utilizing transition metals and Lewis acids are important synthetic tools for the formation of C–C and C–N bonds and a number of cross-coupling reactions between α-bromo carbonyl compounds and metal reagents such as aryl metals, alkenyl metals, and alkyl metals have been reported. Transition metal-catalyzed cross-coupling reaction for the construction of α-alkynyl carbonyl compounds has reported in a limited case. The first approach to secondary α-alkynyl carbonyl compounds from secondary α-bromo esters and amides with tributyl(phenylethynyl)stannane under palladium-catalyzed cross-coupling reaction conditions was developed. This synthetic method allows access to secondary α-alkynyl carbonyl compounds which are valuable precursors in pharmaceuticals and agricultural applications.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / This PhD thesis describes our results on the application of indium(I) bromide in carbon-carbon bond forming reactions. Indium enolates, generated in situ from the reaction between indium(I) bromide and α,α-dichloroketones, react with carbonyl compounds and electron-deficient alkenes. Reactions of indium enolate with α,α-dichloroketones, in presence of extra InBr, leads to the formation of 1,4-diketones. The coupling with aldehydes leads alternatively, according as the stoichiometry, to the diastereoselective synthesis of (syn+anti)-2-chloro-3-hydroxy-propan-1-ones (which can be converted to the respective trans-epoxyketones), (E)-α,β-unsaturated ketones and cyclopropanes, upon a sequenced reaction mechanism. We also have developed a methodology for the preparation of cyclopropanes through the reaction of the indium enolate and other organoindium(III) compounds, derived from the reactions between InBr and α,α-dihalo carbonyl compounds and halo-acetonitriles, with electron-deficient alkenes. / Este trabalho descreve os resultados dos estudos realizados sobre aplicações de brometo de índio(I) em reações para formação de ligações carbono-carbono. A reação entre brometo de índio(I) e α,α-diclorocetonas produz, in situ, enolatos de índio que reagem com compostos carbonílicos e alcenos deficientes em elétrons. As reações do enolato de índio com outras moléculas de α,α-diclorocetonas, na presença de InBr em excesso, leva à formação de 1,4-dicetonas. O acoplamento com aldeídos leva alternativamente, conforme a estequiometria, à formação diastereosseletiva de (syn+anti)-α-cloro-β-hidróxi-cetonas (que podem ser convertidas às respectivas trans-epóxi-cetonas), cetonas (E)-α,β-insaturadas e ciclopropanos, segundo um mecanismo de reações sequenciais. Ainda foi desenvolvida uma metodologia para preparação de ciclopropanos através da reação do enolato de índio e de outros compostos organoíndio(III), derivados da reação entre InBr e vários compostos carbonílicos α,α-di-halogenados e halogeno-acetonitrilas, com alcenos deficientes em elétrons.

Les dérivés cyclopropanoïques sont des composés importants dans plusieurs domaines tels que la synthèse organique, la chimie médicinale et la science des matériaux. La synthèse asymétrique des dérivés cyclopropanoïques s'est de plus en plus concentrée sur la synthèse stéréocontrolée de cyclopropanes polysubstitutés qui arborent toute une gamme de substituants distincts. Ces méthodes permettent d’accéder à des synthèses divergentes pour préparer des composés pharmaceutiques comportant cette sous-unité. De plus, l'ouverture facile de ce cycle très tendu en fait une bonne cible pour étudier l'activation de la liaison C‒C. C’est pourquoi les cyclopropanes sont parmi les composés les plus attrayants et les plus diversifiés en synthèse organique. La synthèse divergente de dérivés cyclopropanoïques repose sur l'utilisation de précurseurs stables mais réactifs. L'une des réactions pour former des liaisons C‒C les plus couramment utilisées dans la fonctionnalisation à un stade avancé, est la réaction de couplage croisé de Suzuki-Miyaura. C'est l'une des raisons pour lesquelles les borocyclopropanes sont devenus des précurseurs synthétiques attrayants pour la fonctionnalisation et diversification des molécules complexes. L’accès à de telles molécules faciliterait la préparation de molécules cyclopropanoïques de structures diversifiées. Il est difficile de préparer des borocyclopropanes de manière énantiosélective. Dans cette thèse, une cyclopropanation énantiosélective d'acides boroniques protégés dérivés d'alcools allyliques a été réalisée via la réaction de cyclopropanation asymétrique en présence du ligand chiral de type dioxaborolane. Le développement de cette méthodologie a nécessité une modification de la décomplexation oxydative existante du dioxaborolane via son complexe dérivé de la diéthanolamine. Le protocole est maintenant applicable aux dérivés boronates qui incluent des groupements fonctionnels qui sont incompatibles avec les bases. Les borocyclopropanes tétracoordonnés obtenus permettent également la formation de liaisons C‒C et ont démontré une stabilité améliorée par rapport à leurs dérivés tricoordonnés. Une étude plus approfondie sur des complexes cyclopropylméthylamine-boranes (CAB) a démontré que ces derniers pouvaient conduire aux amine-boranes spirocycliques (SCAB). Ces SCAB ont été obtenus grâce à une cascade d'activation des CABs en utilisant le bis(trifluorométhanesulfonimide) (Tf2NH) comme initiateur. L'ouverture du cycle des CAB représente la première conversion des cyclopropanes en spirocycles contenant à la fois un N-spirocentre et un spiro amine-borane. Les amine-boranes ont démontré une activité pharmacologique telle que des propriétés anticancéreuses, anti-inflammatoires et anti-ostéoporotiques. L'incorporation de spirocycles dans un motif augmente le caractère sp3 et la chiralité inhérente. Les SCAB rendent alors des candidats attrayants pour la conception de médicaments. La réaction de SCAB avec de Tf2NH en quantités stoechiométriques a donné un complexe SCAB•NTf2 qui est capable de réduire les fonctions cétone, aldéhyde, imine, nitrobenzène, nitrosobenzène, anthracène, indole et aryl méthyl éther. Le complexe SCAB•NTf2 est également capable de réduire le diphénylacétylène de manière Z-sélective en cis-stilbène. Des études spectroscopiques approfondies ont donné plus d'informations sur la structure de SCAB•NTf2 et nous ont permis de proposer un mécanisme de réduction des groupements fonctionnels ci-dessus. Les études spectroscopiques (RMN, IR et Raman) ont également révélé l'implication d'une liaison α-C‒H au bore dans une liaison hydrogène hypsochromique « improper hydrogen bond » avec [Tf2N]-. L'hyperconjugaison avec l’atome de bore, un acide de Lewis, est proposée, ce qui rend la liaison C‒H acide et donc suffisamment polarisée pour agir comme un donneur de pont hydrogène. / Cyclopropane derivatives are incredibly versatile building blocks used in organic synthesis, medicinal chemistry, and materials science. The asymmetric synthesis of cyclopropane derivatives has increasingly focused on achieving polysubstituted cyclopropanes with a range of distinct substituents and their use in divergent syntheses to access pharmaceutical compounds. Moreover, the ring-opening potential of the cyclopropane ring, due to its inherent strain, makes it a facile target for C‒C bond activation and one of the most attractive and diverse cycloalkanes in organic synthesis. Divergent synthesis of cyclopropanes relies on stable pre-installed handles on cyclopropanes that can be activated readily. One of the most common C‒C bond formation approaches used in late-stage functionalization is the Suzuki-Miyaura cross-coupling reaction. As a result, borocyclopropanes have become attractive synthetic building blocks for their use in late-stage functionalization. Methods for the enantioselective synthesis of borocyclopropanes are scarce. In this thesis, the first enantioselective cyclopropanation of an allylic alcohol bearing a tetracoordinate boronate has been achieved via the Charette dioxaborolane-mediated enantioselective cyclopropanation reaction. The development of our method required modification of the existing oxidative decomplexation of dioxaborolane via diethanolamine. The protocol has now been expanded to include boronates and base-sensitive functionalities. The tetracoordinate borocyclopropane obtained was also shown to undergo C‒C bond formation and demonstrated enhanced stability compared to its tricoordinate boronate derivative. Further investigation of boron tethered cyclopropanes led to the discovery of the unique transformation of cyclopropane amine-boranes (CABs) to spirocyclic amine-boranes (SCABs). SCABs were obtained through a cascade activation of CAB via bis(trifluoromethane)sulfonimide (Tf2NH). The ring-opening of CABs represents the first conversion of cyclopropanes to spirocycles containing an N-spirocenter and furthermore an amine-borane spirocore. Amine-boranes have shown pharmacological activity such as anti-cancer, anti-inflammatory, and anti-osteoporotic properties. Incorporating spirocycles into a motif increases sp3 character and inherent chirality, rendering SCABs as attractive candidates for drug design. The reaction of SCAB with stoichiometric amounts of Tf2NH resulted in a SCAB•NTf2 complex that was found to be able to reduce ketone, aldehyde, imine, nitrobenzene, nitrosobenzene, anthracene, and indole functionalities as well as demethylate aryl methyl ethers. The SCAB•NTf2 complex was also capable of reducing diphenylacetylene in a Z-selective manner to cis-stilbene. In-depth spectroscopic studies revealed the structure of SCAB•NTf2 and a mechanism for the reduction of the above functionalities is proposed. The spectroscopic studies (NMR, IR and Raman) revealed the involvement of an α-C‒H bond to boron in improper hydrogen bonding with [Tf2N]-. Hyperconjugation to the Lewis acidic boron is proposed to make the C‒H bond acidic and therefore polarized enough to act as a hydrogen bond donor.