La famille des phytoalexines est formée de molécules constituant une réponse de certains végétaux à différentes agressions comme par exemple, une attaque fongique, lexposition au rayonnement ultraviolet ou à lozone. Parmi les membres de cette famille, on trouve notamment le resvératrol, le picéatannol, les combretastatines et encore bien dautres composés dont la structure est basée sur un motif stilbénique. Ces dérivés possèdent des propriétés pharmacochimiques dun grand intérêt dans de nombreux domaines comme ceux des antioxydants, des antibactériens, des antiviraux et également dans la lutte contre le cancer et le diabète. La synthèse chimique est la voie la plus économique pour produire en masse ces substances. Parmi les nombreuses méthodes de synthèse mises au point, nous avons évalué la réaction de couplage décarbonylatif de Heck entre un ester dénol et un dérivé du styrène. Cette voie catalytique se base sur lutilisation de réactifs bon marché et conduit à la formation dacétone et de monoxyde de carbone comme uniques sous-produits. Ce couplage décarbonylatif ainsi que la synthèse préalable dun ester dénol ont été étudiés afin dêtre optimisés.

A catalytic (in Brønsted superacid) and a stoichiometric process were developed to synthesise aryl boronic esters with boron cations via electrophilic arene borylation. The treatment of CatBX (Cat = catecholate; X = Cl, Br) with the triethyl salt [Et3Si][closo-CB11H6Br6] in arene solvent gave a transient boron electrophile that reacted as a synthetic equivalent of [CatB]+ in intermolecular electrophilic aromatic borylation at 25 °C. The by-product of the reaction was a strong Brønsted acid that was able to catalyse arene borylation using CatBH at high temperature. This catalytic process furnished aryl boronic esters in high yield with H2 as the only by-product. The use of the robust and weakly coordinating anion [closo-CB11H6Br6]- and the electrophile-resistant catecholborane were crucial for the catalytic process. The reaction mixture of R2BCl (R2 = Cat, Cl4Cat, Cl2), aprotic amine and AlCl3 mainly gave a borenium salt [R2B(amine)][AlCl4] which was in equilibrium with neutral species as revealed by NMR spectroscopy and reactivity studies. This reaction mixture was effective for the regioselective borylation, by electrophilic aromatic substitution, of a range of N-heterocycles, thiophenes and anilines at room temperature. The transterification in situ provided the synthetically useful and more stable pinacol boronate esters in excellent isolated yield. This process displayed remarkable functional-group tolerance for a boron based strong Lewis acid with weak bases (for example -NMe2), ether, and halogen groups all compatible. This process represents a new and inexpensive one-pot direct arene borylation methodology for producing pinacol boronate esters.

Manganese is amongst the most abundant transition metals on earth. Playing several roles in enzymatic function, manganese is largely considered biocompatible and, in comparison to most transition metals, it is relatively inexpensive. It is surprising then, that manganese remains poorly explored in the field of pincer-based homogenous catalysis. PN3(P) pincer ligands have proved to impart different kinetic and thermodynamic properties to the complexes they are a part of when compared to analogous complexes of ligands with CH2 spacers. In part I of this work, we present unexpected results from a thorough investigation of the coordination chemistry between a PN3 phenanthroline-based ligand and several manganese salts that suggest that the coordination environment may promote a disproportionation reaction. We also present an efficient route towards dichloride substituted PN3 manganese complexes. In Part II, we investigate the reactivity of manganese(II) pincer compounds in ester reduction reactions and probe the promising results afforded by reduction through borohydride.

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Amine-functionalized boronic acids have revolutionized the field of carbohydrate sensing in recent years. Capable of rapidly and reversibly forming cyclic boronate esters with of 1,2- and 1,3-diols, polyols, catechols, and α-hydroxycarboxylic acids, boronic acids have found applications spanning from lipid transport to Hydrogen fuel cells. The majority of the work presented in this dissertation will be aimed at gaining a better understanding of the Boron-Nitrogen interactions in ortho-aminomethyl functionalized boronic acids. Chapter 2 will provide an overview of the mechanistic understanding of boronic acid-diol interactions with a special focus on amine-functionalized boronic acids. Chapters 3 – 5 report the progress made by the Anslyn group to develop a more thorough understanding of Boron-Nitrogen interactions and how they affect boronate ester formation. The first introductory chapter will present a the recent advances that have been made in the development of pattern-based sensor systems. Finally, chapter 6 will present the synthesis of a series of bicycloguanidinium hosts, which will be used in a sensing array for chiral carboxylates. / text

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The development of artificial metal-based catalytic systems for phosphate ester hydrolysis is the central focus of this work. Currently, significant efforts are concentrated in this field of research as phosphate esters are remarkably stable linkages and are found in the molecules of life DNA and RNA, as well as in toxic compounds, such as nerve agents, pesticides and herbicides. The thesis describes the design and synthesis of a series of N-functionalised azamacrocyclic ligands suitable for metal chelation. An efficient strategy is described, where an aminal precursor is used for the selective N-alkylation of a cyclen moiety, in order to obtain non-bridged and ethylene-bridged cyclen-based ligands. Thereafter, the synthesis of the tetraamine Co(III) and Zn(II) aqua-hydroxo complexes is detailed, followed by a study of the coordination chemistry of Co(III)-based cyclen complexes. Moreover, the redox behaviour of such complexes is investigated by means of cyclic voltammetry. The hydrolytic activity of these complexes towards phosphate ester substrates is then presented. The hydrolytic activity of the cyclen-based Co(III) complexes is shown to be extremely sensitive to modest changes in the ligand structures, even though they do not affect the coordination geometry. Cyclen-based Zn(II) complexes appear to have no appreciable activity towards hydrolysis of phosphate mono- and di-esters under the same experimental conditions. The effect of incorporating polymerisable tetraamine Co(III) complexes into the nanogels on their hydrolytic efficiency is also investigated using molecular imprinting technique. The design and synthesis of structurally similar tripodal 'click' ligands, suitable for the preparation of a range of d-block metal complexes is then presented. The coordination chemistry of the complexes of these structurally similar ligands is explored using a range of techniques including single crystal X-ray crystallography, EPR and UV-Vis spectroscopies and cyclic voltammetry. Due to their poor aqueous solubility various ways to improve this are also examined. Future developments of the metal-based catalysts are then discussed including key issues to be addressed to achieve their potential applications in biological systems.

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