Sang-Han Kim

Immobilization of new Mn(salen) complex over MCM-41 and its activity in asymmetric epoxidation of styrene

New tetradentate chelates of bis-Schiff bases were synthesized and then these chiral salen ligands were immobilized over mesoporous MCM-41 by using the ion-exchange method. The efficiency of the chiral catalyst was examined in the asymmetric epoxidation of styrene. Chiral Mn(salen) complexes immobilized onto mesoporous MCM-41 were stable during the reaction without any leaching and exhibited relatively high enantioselectivity for epoxidation as compared with homogeneous complexes.

New enantioselective chiral imidazolidine ligands for Pd-catalyzed asymmetric allylic alkylation

Abstract Chiral imidazolidine ligands have been synthesized from N,N ′-dialkylated cyclohexanediamine derivatives and they were found to act as effective ligands in the palladium-catalyzed asymmetric allylic substitution. The excellent levels of enantiomeric excess up to 98% were obtained in high yield.

N,N′-Dialkylated 1,2-diamine derivatives as new efficient ligands for RuCl2(PPh3)3 catalyzed asymmetric transfer hydrogenation of aromatic ketones

Abstract Chiral N,N′-dialkylated cyclohexanediamine derivatives ligands have been synthesized and used in an asymmetric transfer hydrogenation of aryl ketones. Optically active alcohols with up to 93% enantiomeric excess were obtained in high yield.

New chiral phosphinoimidazolidine ligand in palladium-catalyzed asymmetric allylic substitution

Chiral phosphinoimidazolidine 3 was used as an excellent ligand in Pd-catalyzed asymmetric allylic alkylation of racemic 1,3-diphenyl-2-propenyl acetate 5 with dimethyl malonate. Outstanding enantioselectivity of up to 99% and remarkable catalytic activity were observed. The ligand was also found to be effective in the asymmetric allylic amination of 5 with benzylamine.

Simultaneous separation and enantioselective hydrolysis reaction of epoxides in membrane system containing chiral polymer salen catalyst immobilized on MCM-41

Very high yield of optically pure epichlorohydrin (ECH) was obtained enantioselectively in the catalytic membrane system having chiral polymer salen complexes, due to simultaneous separation of the product during the reaction. The hydrophobic epoxide product diffuses across the membrane into the organic solvent phase.

MCM-41-supported norephedrine ligand for ruthenium-catalyzed asymmetric transfer hydrogenation of ketones

Abstract Optically active norephedrine was anchored on MCM-41 silica material. The insoluble system was utilized as an enantioselective ligand in the asymmetric transfer hydrogenation of ketones. This reaction provided ( R )-secondary alcohols with satisfactory enantioselectivities (up to 95% ee) in good conversion. The results are comparable to those of the analogous homogeneous counterpart.