Estudio de la reacción de hidroformilación de sustratos orgánicos con catalizadores de rodio (I)

Abstract

En esta memoria se presenta un estudio de la reacción de hidroformilación con complejos de rodio(I), que constituye el primer trabajo sobre hídroformilación que se lleva a cabo en el Departamento de Química de esta Facultad.<br/><br/>Se ha estudiado el sistema [Rb(mi)S(CH(2))3NMe(2)(COD)]2/n PR3 en la hidroformilación de 1-hexeno, incluido la influencia de la naturaleza y del exceso de ligando auxiliar. Así mismo, se ha investigado la reacción de hidroformilación de dihidropiranos y dihidrofuranos como modelos para la posterior hidroformilación de glicales. La utilización de ligandos auxiliares voluminosos y el estudio del efecto de las diferentes condiciones de reacción ha permitido obtener resultados satisfactorios en cuanto a conversiones y selectividades.

<i>Hydroformylation of complex molecules using organometallic catalysts is a field of increasing interest. Since rhodium is more active than cobalt, the reaction parameters can be widely varied, thus allowing better control of the reaction.<br/><br/>We have developed a new type of catalyst precursors by addition of different molar ratios of phosphorus ligands to the dimeric complex [Rb(mi)S(CH(2))3NMe(2)(COD)]2/n(1). These systems catalyse the hydroformylation of hex-I-ene to give heptanal in goog yield and selectivity. Owing to the presence of the amine group the rhodium catalyst can be quantitatively recovered as [Rb(mi)S(CH(2))3NMe(2)(COD)]2/n (SO(4)).<br/><br/>We also report on the hydroformylation of enol eters, such dibydrofurans, dihydropyrans and glycals, using the rhodium precursor (1) and PR3. The influence of the reaction conditions, the nature and the amount of PR3 on the conversion and the quimio, regio and stereoselectivity of the reaction has also been studied.<br/><br/>Dihydrofurans are completly hydroformylated under mild conditions, and fine tuning of reaction conditions allows the control of the regioselectivity.<br/><br/>Dihydropyrans require more drastic conditions than dihydrofurans and only important yields are obtained when a bulky auxiliary Iigand was used.<br/><br/>Glycals can be also hydroformylated to aldehydes with good yields, regio and stereoselectivities using bulky auxiliary ligands. The regioselectivity observed well determinated by the highly polarized double bond and the stereoseleclivity by steric shieldings, yielding branched sugars in the C-2 with the formyl group on the more stericaly open face of the molecule. </i>