New Chiral Ligand Derived from (+)- -Pinene Used in the Enantioselective Addition of Diethylzinc to Aldehydes

Several examples have been reported for highly enantioselective alkylation of aldehydes by organometallic compounds combined with chiral modifiers. In general, dialkylzincs present low reactivity towards carbonyl compounds, but their reactivity can be enhanced by the structural modification by appropriate ligands or auxiliaries. Replacement of one alkyl group by an electronegative substituent increases the acceptor character of the zinc atom and the donor property of the remaining alkyl group, thereby accelerating the reaction with carbonyl substrates 1 . Here we report our results involving the addition of diethylzinc to some aromatic aldehydes using a compound derived from α-pinene (1) as chiral auxiliary.