Polymer-bound N-alkylnorephedrines as efficient chiral catalysts for the enantioselective addition of dialkylzincs to both aromatic and aliphatic aldehydes
Polymer-bound N-alkylnorephedrines are recyclable catalysts of the enantioselective addition of dialkylzincs to both aromatic and aliphatic aldehydes. Optically active aromatic and aliphatic secondary alcohols are obtained in high enantiomeric excess. The catalyst derived from N-methylnorephedrine (ephedrine) affords aliphatic alcohols of up to 89% e.e. in the alkylation of aromatic aldehydes. On the other hand, the catalyst derived from N-ethylnorephedrine affords up to 80% e.e. in the alkylation of aliphatic aldehydes.