Synthesis of Chiral Bis(dihydrooxazolylphenyl)oxalamides, a New Class of Tetradentate Ligands for Asymmetric Catalysis
摘要:
Enantiomerically pure N,N'-bis[2-(4,5-dihydrooxazol-2-yl)phenyl]oxalamides are readily prepared from 2-(2-aminophenyl)-4,5-dihydrooxazoles and oxalyl chloride. The structures of the corresponding nickel and copper complexes were determined by X-ray analysis. Ruthenium complexes, prepared in situ from RuCl3 and the corresponding ligands, catalyze the enantioselective epoxidation of trans-stilbene to afford trans-1,2-diphenyloxirane with up to 69% ee. The cobalt complexes were tested as catalysts in Michael reactions of malonates with chalcone (up to 89% ee).
Enantiomerically pure N,N'-bis[2-(4,5-dihydrooxazol-2-yl)phenyl]oxalamides are readily prepared from 2-(2-aminophenyl)-4,5-dihydrooxazoles and oxalyl chloride. The structures of the corresponding nickel and copper complexes were determined by X-ray analysis. Ruthenium complexes, prepared in situ from RuCl3 and the corresponding ligands, catalyze the enantioselective epoxidation of trans-stilbene to afford trans-1,2-diphenyloxirane with up to 69% ee. The cobalt complexes were tested as catalysts in Michael reactions of malonates with chalcone (up to 89% ee).
Coupling of Bulky, Electron-Deficient Partners in Aryl Amination in the Preparation of Tridentate Bis(oxazoline) Ligands for Asymmetric Catalysis
作者:Helen A. McManus、Patrick J. Guiry
DOI:10.1021/jo0262558
日期:2002.11.1
o-substituted coupling partners, 2-(2'-bromophenyl)oxazolines 8 and 2-(o-aminophenyl)oxazolines 9. By varying the substituent on the coupling partners, a range of 10 ligands has been prepared in good yield. During the synthesis of 2-(o-aminophenyl)oxazolines 9a-d, a number of products of unexpected side reactions were isolated in two of the three steps. Alternatively, the required 2-(o-aminophenyl)oxazolines