New Axially Chiral Bis(dihydrooxazoles) as Ligands in Stereoselective Transition‐Metal Catalysis

Abstract

Abstract The new, axially chiral bis(4,5‐dihydrooxazoles) 4 have been synthesized in a straightforward manner, starting from the substituted, racemic 1,1′‐biphenyl‐2,2′‐dicarboxylic acids 1 and optically active amino alcohols 2 . The adducts were resolved by medium‐performance liquid chromatography (MPLC; see Scheme 1 ). Formation of Cu 1 complexes of 4 was followed by 1 H‐NMR spectroscopy. The catalytic behavior of these complexes has been investigated by asymmetric cyclopropanation of styrene with ethyl diazoacetate. Beside the influence of steric factors, a significant electronic effect on asymmetric induction could also be observed (see Scheme 2 and Table ).