Toward a rational design of the assembly structure of polymetallic asymmetric catalysts: design, synthesis, and evaluation of new chiral ligands for catalytic asymmetric cyanation reactions
作者:Ikuo Fujimori、Tsuyoshi Mita、Keisuke Maki、Motoo Shiro、Akihiro Sato、Sanae Furusho、Motomu Kanai、Masakatsu Shibasaki
DOI:10.1016/j.tet.2007.02.081
日期:2007.6
New chiral ligands (4 and 5) for polymetallic asymmetric catalysts were designed based on the hypothesis that the assembled structure should be stable when made from a stable module 8. A metal-ligand 5:6+mu-oxo+OH complex was generated from Gd((OPr)-Pr-i)(3) and 4 or 5, and this complex was an improved asymmetric catalyst for the desymmetrization of meso-aziridines with TMSCN and conjugate addition of TMSCN to alpha,beta-unsaturated N-acylpyrroles, compared to the previously reported catalysts derived from 1-3. These two groups of catalysts produced opposing enantioselectivity even though the ligands had the same chirality. The functional difference in the asymmetric catalysts is derived from differences in the higher-order structure of the polymetallic catalysts. (C) 2007 Elsevier Ltd. All rights reserved.