Study On The Asymmetric Synthesis And Regio-selective Hydrolysis Of N-Ts Activated Aziridines

This thesis is mainly compromised of three parts: First, the synthesis of Salen and benzoimidazole types of Schiff base ligands and their complexes formed with rare earth metals; second, the synthetic applications of these complexes in the first example in the asymmetric aziridination of alkenes and the regioselective ring opening of N-Ts aziridines under three efficient and green conditions.In the first part, we synthesized a series of chiral Salen type and benzoimidazole type ligands with different chelating numbers bearing BINOL, natural amino acids and ferrocene motifs. During the process of the synthesis of ferreocene-containing ligands, we obtained the single crystal of N-ferrocenylmethyl-(2-hydroxylmethyl) benzamide and did the X-Ray diffraction studies. In the second part we successfully prepared the complexes of the above mentioned ligands with readily available, inexpensive, and echo-friendly rare earth metals (La, Sm, Eu, Yb) and for the first time applied these complexes in the asymmetric aziridination of alkenes. Using chloroamine T as the nitrogen transfer reagent, we examined different factors that might influence the chemical yield. We proposed that the amount of solvent rather than the anhydrous environment and the use of excess of olefins is the key factor in obtaining high yields. After careful screening of reaction conditions including ligands and metals, we were able to improve the e.e. of the product to 37%. We surmised that the secondary orbital interactions between chiral catalyst and substrate would be key to improving the enantioselectivities. The third part of this thesis is the regioselective ring-opening of azidirines with water as the nucleophile, in which three conditions were developed. Water is used as the nucleophile and solvent, the ring-opening of N-Ts aziridine proceeds without the assistance of catalysts, indicating that this is a SN1 process. In the aqueous solution of polyacrylamide as the reaction media the ring-opening reaction of N-Ts aziridine could finish within 30 min affording the products in over 90% yields. An explanation was given for this phenomenon. We also discovered that the recovered polyacrylamide solution showed different regioselectivity in the reaction of different types of aziridines. We have also discovered that the copolymer CPS (acrylic acid, butyl acrylate and styrene) could serve as phase transfer catalyst in the ring-opening reaction of azidirines. A systematic optimization of reaction conditions was carried out, including catalyst loading, reaction temperature and reaction time, etc. to obtain the optimal conditions.In addition, this thesis also includes the development and optimization of a process of a ten-step, scalable synthesis of anti type II diabetes drug PPARα/γdual antagonist.