New Atropisomeric Amino Alcohol Ligands for Enantioselective Addition of Diethylzinc to Aldehydes

Efficient synthesis of several new atropisomeric amino alcohols having 1-phenyl-1H-pyrrole skeleton are reported. Steric arrangements of the products were confirmed by a single-crystal X-ray measurement. The consequences of the size of the N-substituents on enantioinduction were examined by employing the enantioselective catalytic addition of diethylzinc to a series of substituted benzaldehydes (yields 91-97%, up to 85% enantiomeric excess). The special effect of the ortho methoxy group of the substrate on the enantioinduction is also interpreted.