New Type of Aldol Condensations Catalyzed by Metal(II) Complexes of α-Amino Acid Esters and that with Cyclodextrin System

Article abstract of DOI:10.1246/bcsj.58.1401

The aldol condensation of p-nitrobenzaldehyde with acetone catalyzed by metal ccomplexes of α-amino acid esters proceeded under mild and neutral conditions to afford an enantiomeric excess aldol-type products, 4-hydroxy-4-(4-nitrophenyl)-2-butanone, along with same dehydrated products without any by-product.The most effective catalyst system was a zinc(II) complex of the tyrosine ethyl ester, Zn(II)-(TyrOEt)2 in MeOH.Complexes of the second-row transition metals were inadeguate for the reactions.Reactions at 30-40 deg C for 24 h were fovorable regarding the asymmetric induction.An H2O solvent was the best for aldol-type product formation without asymmetric induction.An assistand effect of cyclodextrins(especially, β-CD) on the catalysis of the Zn(II)-TyrOEt complex were thought to be observed.