1,1′-Binaphthylazepine-based ligands for the enantioselective dialkylzinc addition to aromatic aldehydes

The new 1,1'-binaphthylazelpine ligand 1c has been prepared and tested in the enantioselective addition of Et(2)Zn to arylalclehydes, allowing us to reach ee's up to 97% and giving extremely rapid reactions (10-20 min). Aminoalcohol 1c and the analogous compounds 1a and 1b were then tested in the enantioselective addition of Bu(2)Zn and Me(2)Zn to arylalclehydes. All of the ligands efficiently catalyze the Bu(2)Zn addition to benzaldehyde, providing good yields in short reaction times (2-4 h) and high ee (up to 96%). In the enantioselective methylation of arylalclehydes ligands 1b and 1c gave high yields (88-97%) and good to high (80-90%) ee's. (C) 2008 Elsevier Ltd. All rights reserved.