Enantiomeric recognition of organic ammonium salts by chiral dialkyl-, dialkenyl-, and tetramethyl-substituted pyridino-18-crown-6 and tetramethyl-substituted bispyridino-18-crown-6 ligands: comparison of temperature-dependent proton NMR and empirical force field techniques
Design, Synthesis, and Application of a C2 Symmetric Chiral Ligand for Enantioselective Conjugate Addition of Organolithium to α,β-Unsaturated Aldimine
摘要:
A C-2 symmetric chiral diether ligand, (1R,2R)-1,2-dimethoxy-1,2-diphenylethane was designed and synthesized on the basis of the concept of an asymmetric oxygen atom. Mediated by the chiral diether, high enantioselectivities were achieved in conjugate addition of organolithiums to naphthaldehyde imine and cyclic and acyclic alpha,beta-unsaturated aldimines. The absolute configuration of the product is predictable by the model.