Ligand synthesis for homogeneous catalysis

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Organophosphorus compounds found applications in varied fields of the organic chemistry: they are particularly present in natural compounds such as the deoxyribonucleic acid (DNA) and in the field of catalysis in which their utility is also proven. Thus, this thesis work first focused on the preparation of various phosphorus ligands utilizable in transition metal catalysed reactions. Being given the importance of this type of reaction in organic synthesis, it appears essential to have many ligands at disposal in order to fine-tune and to optimize the reaction conditions as much as possible. Thus, the first objective of this work was to propose a simple and general method for the preparation of monodentate phosphorus ligands. Based on the use of phosphites in substitution for the usual phosphorus trihalides, this method was initially tested during the preparation of different simple triarylphosphines. Thereafter, this method was extended to the synthesis of new ligands having more complex structures. The yields obtained for the latter as well as the variety of the substrates authorized by this method confirmed its value and suggested its application to the synthesis of new heteroaromatic phosphines. The preparation of bidentate phosphorus ligands based on chiral biphenyl motifs was then addressed. For that purpose, the 2,2',6,6' -tetrabromobiphenyl was chosen as a pivot substrate for the development of a modular synthetic approach. Indeed, by means of successive halogen/metal permutational exchanges and after treatment with the suitable electrophile, it was possible to functionalize this substrate, isolate each atropisomer in enantiomerically pure form, and finally convert each one of those into chiral biphenylbisphosphines. In addition, it was also possible, during the synthesis of these ligands, to evaluate the rotational stability of some enantiomerically pure dilithiobiphenyls by means of dynamic nuclear magnetic resonance experiments.