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

摘要

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+μ-oxo+OH complex was generated from Gd(OiPr)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 α,β-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.