| The design and synthesis of new chiral catalyst with high reactivity as well as excellent enantioselectivity have played a significant role in the development of the asymmetric catalytic reactions. In this dissertation, we first synthesized several chiral aminophosphine-Ir(I) complexes using the interaction of [IrCl(cod)]2 with chiral tetradentate aminophosphine ligands. The new chiral iridium(I) complex catalysts were successfully applied to asymmetric transfer hydrogenation of various aromatic ketones and oxidative kinetic resolution of racemic secondary alcohols.1. The interaction of [IrCl(cod)]2 with two equivalents chiral tetradentate aminophosphine ligands C6P2N2 or CeP2(NH)2 in a 1:1 mixture of benzene-methanol at room temperature gave corresponding chiral aminophosphine-Ir(I) complexes, which were characterized by EA, IR, NMR and CD. The workup procedure is simple and the complexes are stable with respect to air and water.2. The new chiral iridium(I) complexes [IrCl-C6P2(NH)2] were applied to catalyze the asymmetric transfer hydrogenation of various aromatic ketones. The results showed that the corresponding chiral alcohols could be obtained with high activity (up to 99% yield) and excellent enantioselectivities (up to 99% ee) under mild conditions. Propiophenone was a preferred substrate with respect to catalytic activity and enantioselectivity in the presence of base. The catalytic turnover reached 4780 mol product/mol iridium and the turnover frequency was as high as 1593 h-1. These results would provide a useful index for further designing practical chiral catalytic systems.However, when other dialkyl ketones were used as substrates, chiral diaminodiphosphine-Ir(I) catalyst did not exhibit a similar high enantioselectivity as found for aromatic ketones, which indicated that the activity and enantioselectivity of the chiral iridium catalyst are very sensitive to the substrate structure.3. We also investigated the enantioselective oxidation of aromatic alcohols catalyzed by chiral aminophosphine-Ir(I) complexes in water. With 'BuOOH as oxidant, the asymmetric oxidation of 1-phenylpropyl alcohol gave high reactivity but no enantioselectivity.4. Chiral diaminodiphosphine-Ir(I) complexes [IrCl-C6P2(NH)2] were found to efficiently catalyze enantioselective oxidation of racemic secondary alcohols in acetone. In the presence of base, oxidative kinetic resolution of the alcohols proceeded smoothly with excellent enantioselectivity (up to 98% ee) under mild conditions. This work presents the first successful use of chiral diaminodiphosphine ligands C6P2(NH)2 and their metal complex catalysts for the oxidative kinetic resolution of racemic secondary alcohols, which provides a valuable extension to the use of chiral diaminodiphosphine ligands in asymmetric catalysis. |
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