Theoretical Investigation of the Asymmetric Alkylation of Benzaldehyde in Presence of Organozinc Reagents

In this paper the asymmetric alkylation of benzaldehyde is revisited by means of semi-empirical and density functional theory based transition state modeling. The reaction proceeds in presence of a dialkylzinc and a b-aminoalkohol which form an amino-coordinated zinc-alkoxide with the benzaldehyde. Then a second equivalent of diethylzinc is added to form a supermolecular transition state for the reaction. Several chiral aminoalkohols have been shown to give a high enantiomeric excesses and the computed stabilities of the supermolecular transition state structures are compared with the available experimental data giving an overall good agreement with the experimental trends.