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Thakur, Santosh Singh,Chen, Shu-Wei,Li, Wenji,Shin, Chang-Kyo,Kim, Seong-Jin,Koo, Yoon-Mo,Kim, Geon-Joong Elsevier 2006 Journal of organometallic chemistry Vol.691 No.9
<P><B>Graphical abstract</B></P><P>Dinuclear chiral salen complexes bearing Lewis acid of group 13 metals catalyze asymmetric ring opening of various terminal epoxides with myriad of nucleophiles via kinetic resolution. The complexes are also found to be active for asymmetric cyclization reaction too.</P><ce:figure></ce:figure> <P><B>Abstract</B></P><P>A new dinuclear chiral Co(salen) complexes bearing group 13 metals have been synthesized and characterized. The easily prepared complexes exhibited very high catalytic reactivity and enantioselectivity for the asymmetric ring opening of epoxides with H<SUB>2</SUB>O, chloride ions and carboxylic acids and consequently provide enantiomerically enriched terminal epoxides (>99% ee). It also catalyzes the asymmetric cyclization of ring opened product, to prepare optically pure terminal epoxides in one step. The homogeneous dinuclear chiral Co(salen) have been covalently immobilized on MCM-41. The potential benefits of heterogenization include facilitation of catalyst separation and recyclability requiring very simple techniques. The system described is very efficient.</P>
( Thakur Santosh Singh ),김건중 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.2
A wide variety of highly selective asymmetric reactions catalyzed by chiral (salen) metal complexes have been disclosed over the past decade. The solvent free hydrolytic kinetic resolution (HKR) of terminal epoxides catalyzed by a new chiral (salen) Co: AlCl3 complex is described. The catalyst shows high reactivity and selectivity in good yields of > 98 % ee under ambient condition within 1 h.
Shon, Jeong-Kuk,Sim, Jae-Yi,Thakur, Santosh Singh,Ko, Eun-Mi,Kong, Soo-Sung,Choi, Ji-Yun,Kang, Min,Senapati, Bidyut Kumar,Choi, Doo-Seoung,Ryu, Do-Hyun,Kim, Ji-Man Korean Chemical Society 2008 Bulletin of the Korean Chemical Society Vol.29 No.10
In the present work, Diels-Alder reaction of cyclopentadiene with ethylacrylate has been carried out by using two types of mesoporous solid acid catalysts (Al-MCM-41, Al-MCM-48) with different pore structures. The specific topology of Al-MCM-48 (cubic Ia3d structure composed of two independent 3-D channel systems) exhibit higher activity and stereo-control than those of Al-MCM-41 (hexagonal packing of 1-D channels). The physical properties of Al-MCM-48 catalyst, such as high accessibility of reactants to the acid sites, spatial confinement in the nanoscopic reactors, and 3-D channel network structure that are effective adsorption and diffusion of reactants, play a crucial role in the present study.
Design of Mesoporous Solid Acid Catalysts with Controlled Acid Strength
Ji Man Kim,Jong-Nam Kim,Jeong Kuk Shon,Xingdong Yuan,고창현,이형익,Santosh Singh Thakur,Min Kang,Min Seok Kang,Donghao Li 한국공업화학회 2007 Journal of Industrial and Engineering Chemistry Vol.13 No.7
Mesoporous silica materials, SBA-15, functionalized with strong (-SO3H), moderate (-PO3H2) and weak (-COOH) acid groups have been successfully prepared by the co-condensation or post-grafting methods. Transmission electron microscopy and powder X-ray diffraction indicate that all of the acid-functionalized SBA-15 materials possess highly ordered mesostructures. These mesoporous acid catalysts have been applied to the alkylation of phenol with tert-butanol. The acid strength as well as the reaction parameters, such as the temperature, space velocity, and molar ratio between the reactants, were found to be the main factors controlling the reactivity and selectivity of the alkylation reaction. SBA-15-SO3H and SBA-15-PO3H2 exhibited much higher catalytic activities than SBA-15-COOH. The product selectivity of alkylation reaction strongly depends on the acid strength as well as the reaction temperature. The SBA-15-SO3H revealed high selectivity for 4-tert-butyl phenol and 2,4-di-tert-butyl phenol at high temperature, whereas the SBA-15-PO3H2 did so for 2-tert-butyl phenol at moderate temperature. Ether was observed at a relatively low reaction temperature over the SBA-15-COOH catalyst.