Development of new reducing system using hypophosphites or calcium hydride : application to the reduction of ketones and to the reaction of reductive amination and alkylation ; Développement de nouveaux systèmes réducteurs utilisant des hypophosphites ou des hydrures de calcium : application à la réduction de cétones ainsi qu’aux réactions d’amination et d’alkylation réductrice

Boron and aluminum hydrides are widely used in organic chemistry allowing the highly chemoselective reduction of complex multifunctional substrates. Other reducing systems developed until now are unable to equal some of these chemoselectivities with competitive costs. The use of boron and aluminum hydrides raises safety, environmental and health concerns. These reactions produce an important quantity of waste which is potentially toxic. The development of alternatives to boron and aluminum hydrides is thus an environmental and economical issue. This PhD work meets these demands by studying the use of hypophosphite derivatives, calcium and magnesium hydride in the reduction of organic functions. These hydrogen donors are stable to air, easy to handle, poorly reactive, inexpensive and are composed of abundant and non-toxic elements. The reduction of ketones to alcohols by sodium hypophosphite was developed in biphasic media in the presence of palladium on carbon or homogeneous ruthenium complexes. The reaction with palladium on carbon led to a mixture of alcohol and alkane. After optimization of the reaction conditions, alcohols were formed selectively. An enantioselective reduction was developed as well using RuCl(p-cymene)-Ts-DPEN as catalyst. Commercial magnesium and calcium hydride have been activated by ball milling and have been tested in the reduction of acetophenone. Calcium hydride has been applied to the reductive amination and alkylation in the presence of catalytic amount of supported platinum or palladium ; Les hydrures de bore et d'aluminium sont très utilisés en chimie organique permettant des réductions hautement chimiosélectives de substrats polyfonctionnels complexes. Les systèmes réducteurs développés jusqu'à nos jours restent incapables d'égaler certaines de ces chimiosélectivités à des coûts compétitifs. L'utilisation des hydrures de bore et d'aluminium pose des problèmes de sécurité, d'environnement et de santé. Leurs réactions génèrent une quantité importante de déchets potentiellement ...