Asymmetric synthesis. Part 6. Asymmetric reduction of aminoketones with (-)-bornan-2-exo-yloxyaluminium dichloride

Abstract

α-Dialkylaminoacetophenones and β-dialkylaminopropiophenones have been reduced asymmetrically with (-)-bornan-2-exo-yloxyaluminium dichloride to the corresponding aminoalcohols in 58-92% enantiomeric excess. The absolute configurations of the predominant enantiomers, (S) and (R) for α- and β-series respectively, follow from six-membered cyclic transition states. Three acetylpyridines have been similarly reduced, but with much less enantioselectivity (12-37%).