Synthesis of Chiral Bis(dihydrooxazolylphenyl)oxalamides, a New Class of Tetradentate Ligands for Asymmetric Catalysis
作者:Nicole End、Ludwig Macko、Margareta Zehnder、Andreas Pfaltz
DOI:10.1002/(sici)1521-3765(19980515)4:5<818::aid-chem818>3.0.co;2-#
日期:1998.5.15
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).