Synthesis And Application In Asymmetric Transfer Hydrogenation Of Ketones Of The New Chiral S-ligands

Chiral secondary alcohols induced from achiral ketones are key intermediates in the industrial and medical production. Asymmetric Transfer Hydrogenation(ATH) of ketones using catalysts based on transition metal complexes of chiral ligands is a classical and favorable way to obtain enantiomerically pure secondary alcohols and the design of novel and versatile chiral ligands have attracted considerable interest of synthetic chemists.Compared to the ligands with P, N or O as donor atoms used in ATH of ketones, sulfur-containing ligands were still much less reported, while the application of sulfur-containing ligands in asymmetric catalysis have proved to be as excellent as other classical chiral ligands. In this thesis, several five-membered ring sulfur-containing ligands have been synthesized and applied in ATH of ketones.A series of chiral tetradentate thiazole ligands were synthesized by the condensation of2-thiazole formaldehyde with readily available (1R.2R)-1.2-cyclohexyldiimine and famous (S. S)-DPEN. Coordinating with Ru, Rh, or Ir, these thiazole ligands were used in ATH of ketones. High conversion were obtained by the catalytic system of Ll/[IrCl(cod)]2-but in most cases, only poor enantioselectivities were achieved. The structure of tetradentate thiazole ligand LI was established by all X-ray diffraction study. As comparison, chiral tetradentate imidazole lisands were also svnthesized bv the same reactions and tested in ATH of ketones.Chiral Schiff base ligands are easily prepared, and wildly used in asymmetric catalytic. The tridentate thiazole ligands (S. S)-1was generated from the condensation of2-thiazole formaldehyde and readily available D-Plenylglycinol. The (S, S)-1/[IrCl(cod)]2catalytic system generated in situ catalyzed the ATH of various ketones with high conversion and good to excellent enantioselectivities (up to99%ee). In order to reveal the catalytic theory, tridentate imidazole and furan ligands were also prepared and used in ATH of ketones. The structure of tridentate imidazole ligand which is structure similar to (S. S)-1was also established by all X-ray diffraction study.