Showing papers by "Sukwon Hong published in 2008"

Self-assembled dinuclear cobalt(II)-salen catalyst through hydrogen-bonding and its application to enantioselective nitro-aldol (Henry) reaction.

Abstract: Novel chiral dinuclear Co(II)-salen catalysts self-assembled through the pyridone/aminopyridine hydrogen-bonding pair have been developed. The self-assembled dinuclear Co(II)-Salen catalyst results in significant rate acceleration (48 times faster rate) as well as excellent enantioselectivity (96% ee vs 55% ee) in a nitro-aldol reaction, compared to the corresponding monomeric catalyst. A bimetallic mechanism is suggested by the kinetic experiment showing that the rate law is second order in [catalyst]. The self-assembly through hydrogen bonding was confirmed by X-ray structure and by the 1H experiments revealing that the dimerization constant of the novel hydrogen-bonding capable salen ligand in 25% v/v CD3NO2/CDCl3 is 53 ± 21 M−1. This result proves the validity of self-assembly based approaches toward the efficient construction of chiral bimetallic catalyst system.

Development of Biisoquinoline-Based Chiral Diaminocarbene Ligands : Enantioselective SN2' Allylic Alkylation Catalyzed by Copper-Carbene Complexes

Abstract: Chiral biisoquinoline-based diaminocarbene ligands (BIQ) were designed to create a chiral environment extended toward the metal center, which was confirmed by an X-ray structure. The concise ligand synthesis is highlighted by a modified Bischler−Napieralski cyclization of bisamides prepared from readily available chiral phenethylamines, and allows easy variation of the stereodifferentiating groups. The cyclohexyl-BIQ−copper complex is an efficient catalyst for enantioselective SN2‘ allylic alkylation with Grignard reagents showing SN2‘ regioselectivity higher than 5:1 and enantioselectivity in the range of 68−77% ee.

Development of Biisoquinoline‐Based Chiral Diaminocarbene Ligands: Enantioselective SN2′ Allylic Alkylation Catalyzed by Copper—Carbene Complexes.

Abstract: Chiral biisoquinoline-based diaminocarbene ligands (BIQ) were designed to create a chiral environment extended toward the metal center, which was confirmed by an X-ray structure. The concise ligand synthesis is highlighted by a modified Bischler−Napieralski cyclization of bisamides prepared from readily available chiral phenethylamines, and allows easy variation of the stereodifferentiating groups. The cyclohexyl-BIQ−copper complex is an efficient catalyst for enantioselective SN2‘ allylic alkylation with Grignard reagents showing SN2‘ regioselectivity higher than 5:1 and enantioselectivity in the range of 68−77% ee.

(R)‐1,1′‐Bi‐2,2′‐naphthotitanium Dichloride

Abstract: (X = Cl) [116051-73-1] C20H12Cl2O2Ti (MW 403.10) InChI = 1S/C20H14O2.2ClH.Ti/c21-17-11-9-13-5-1-3-7-15(13)19(17)20-16-8-4-2-6-14(16)10-12-18(20)22;;;/h1-12,21-22H;2*1H;/q;;;+4/p-4 InChIKey = FPUHPAXGAMEZPA-UHFFFAOYSA-J (X = Br) [128030-80-8] C20H12Br2O2Ti (MW 492.00) InChI = 1S/C20H14O2.2BrH.Ti/c21-17-11-9-13-5-1-3-7-15(13)19(17)20-16-8-4-2-6-14(16)10-12-18(20)22;;;/h1-12,21-22H;2*1H;/q;;;+4/p-4 InChIKey = QVHIDUXZLMFNCL-UHFFFAOYSA-J (X = ClO4) [138645-47-3] C20H12Cl2O10Ti (MW 531.09) InChI = 1S/C20H14O2.2ClHO4.Ti/c21-17-11-9-13-5-1-3-7-15(13)19(17)20-16-8-4-2-6-14(16)10-12-18(20)22;2*2-1(3,4)5;/h1-12,21-22H;2*(H,2,3,4,5);/q;;;+4/p-4 InChIKey = KGTZOTWFWGDVPQ-UHFFFAOYSA-J (X = OSO2CF3) [139327-61-0] C22H12F6O8S2Ti (MW 630.32) InChI = 1S/C20H14O2.2CHF3O3S.Ti/c21-17-11-9-13-5-1-3-7-15(13)19(17)20-16-8-4-2-6-14(16)10-12-18(20)22;2*2-1(3,4)8(5,6)7;/h1-12,21-22H;2*(H,5,6,7);/q;;;+4/p-4 InChIKey = JYNWYDFSSZSDQJ-UHFFFAOYSA-J (chiral Lewis acid for ene reactions,2 Mukaiyama aldol reactions,16 Diels–Alder reactions,24 and cyanosilylations27) Alternate Name: BINOL-TiX2. Solubility: insol propionitrile; sol toluene, dichloromethane, and nitroethane. Handling, Storage, and Precautions: titanium is reputed to be of low toxicity.