1,1 '-binaphthyiazepine-based ligands for asymmetric catalysis. Part 2: New aminoalcohols as chiral ligands in the enantioselective addition of ZnEt2to aromatic aldehydes

The new enantiopure 1,2-aminoalcohols 1b-1h having 1,1 ' -binaphthylazepine skeleton have been tested as catalytic precursors in the enantioselective addition of ZnEt2 to benzaldehyde. The best results were seen with ligand 1 d, which owes its chirality only to the atropisomerism of the binaphthyl nu cleus and does not have any stereogenic carbon atom. In the presence of 1d benzaldehyde was quickly and cleanly transformed to (S)-1-phenylpropanol in 99% yield and 87% e.e. The same ligand was also used in the asymmetric ZnE t2 addition to other aryl aldehydes giving rise to (S)-1-arylpropanols in a lmost quantitative yields and e.e.s up to 90%. (C) 2001 Elsevier Science Lt d. All rights reserved.