Enantioselective ethylation of benzaldehyde with diethylzinc in the presence of a catalytic amount of chiral piperazine derivatives was investigated. The chiral piperazine works as an asymmetric catalyst in the alkylation, yielding 1-phenylpropanol with a moderate enantioselectivity. The influence of structural variation of the piperazine ring upon the asymmetric induction and the mechanism involved are discussed.