• Applied Chemistry for Engineering
• /
• v.20 no.3
• /
• pp.279-284
• /
• 2009

The formation of mesoporous pores in the microporous mordenite crystals was performed by controlled silica extraction on alkaline treatment. Inner tunable mesopore size could be controlled by changing the concentration of alkaline solution. The pore structure of mordenite zeolite was studied by instrumental analysis after alkaline-treatment. To obtain the cage type mesopores, Ti-coating on the ourside mordenite crystals before alkaline treatment was investigated to be the most effective. Polymeric chiral salen Co (III) complexes were successfully encapsulated in mesoporous mordenite zeolite by "ship-in-a-bottle" method. The heterogeneous catalyst could be applied in asymmetric ring opening of epichlorohydrine by water. It showed very excellent enantioselectivity with a high yield in the catalysis.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.spc8
• /
• pp.2965-2969
• /
• 2011

Highly efficient and rapid aminolysis of epoxides with various amines in water under microwave irradiation in the absence of catalyst was developed. Chiral ${\beta}$-amino alcohols were formed in a short time with excellent yields.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.9
• /
• pp.3274-3280
• /
• 2011

Monodispersed porous NiO and $Co_3O_4$ microcapsules with a hollow core were synthesized using SBA-16 silica sol and PS as a hard template. The porous hollow microcapsules were characterized by XRD, TEM and $N_2$ adsorption/desorption analysis. After $H_2$ reduction of metal oxide microspheres, they were conducted as an active catalyst in the reduction of chiral butylronitrile and cyanobenzene. The mesoporous metals having a hollow structure showed a higher activity than a nonporous metal powder and an impregnated metal on the carbon support.

• Bulletin of the Korean Chemical Society
• /
• v.24 no.2
• /
• pp.225-228
• /
• 2003

• Archives of Pharmacal Research
• /
• v.27 no.2
• /
• pp.136-142
• /
• 2004

In this study, a highly diastereoselective synthesis of anti-1 ,2-aminoalcohol was explored starting from L-amino acids as chiral sources. The higher yield and diastereoselectivity was shown when the aza-Claisen rearranqement was performed with allylic trichloroacetimidate 6a in the presence of palldium(II) catalyst.

• Journal of the Korean Magnetic Resonance Society
• /
• v.27 no.2
• /
• pp.10-15
• /
• 2023

The Strain-Promoted Azide-Alkyne Cycloaddition (SPAAC) is a powerful method for synthesizing triazoles, even under physiological conditions, without a copper catalyst. This technique provides an efficient means for everyone to synthesize complex triazole derivatives rapidly. In order to investigate the configuration of triazole derivatives using bicyclo[6.1.0.]-nonyne (BCN) and chiral azide, it is necessary to employ the 2D NMR. Both 1D and 2D NMR (COSY, HSQC, ¹⁵N HMBC) are used to analyze the complex triazole product containing cyclooctyne, a diastereomeric product. The stereometric difference of the proton bonded to the same carbon is determined through the HSQC assignment. The intriguing splitting pattern of carbon resonances also reveals their diastereomeric configuration and will aid in further research based on physiological knowledge.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.9
• /
• pp.2649-2654
• /
• 2014

Synthesis of north-5'-methylbicyclo[3.1.0]hexyl adenine and hypoxanthine nucleosides with an ethenyl group at C3' position was successfully achieved by a highly facile method. Methylbicyclo[3.1.0]hexanone (${\pm}$)-7 with three contiguous chiral centers and its epimer (${\pm}$)-6 was remarkably simply constructed only by four steps involving a carbenoid insertion reaction in the presence of rhodium (II) acetate dimer as a metal catalyst, giving a correct relative stereochemistry of the generated three chiral centers. Due to steric hindrance from the concave face of the bicyclo[3.1.0]hexanone system, a Grignard reaction of (${\pm}$)-7 with ethenylmagnesium bromide showed exclusive diastereoselectivity towards the b-face. The Grignard reaction chemoselectively proceeded without reacting with ester functionality. Coupling reaction of glycosyl donor (${\pm}$)-11 with 6-chloropurine nucleobase afforded only the desired $N^9$-alkylated nucleoside without the formation of $N^7$-regioisomer. By the conventional method, 6-chloro group was converted into 6-amino and 6-hydroxy groups to give the desired adenine and hypoxanthine bicyclo[3.1.0]hexyl carbanucleosides with 3'-ethenyl group, respectively.

• Applied Chemistry for Engineering
• /
• v.30 no.3
• /
• pp.365-370
• /
• 2019

In this study, effects of the ultrasonic irradiation during the reaction process were investigated for the enantioselective kinetic resolution (EKR) reaction of racemic epoxides in the presence of chiral cobalt salen catalysts, as compared to that of using the conventional mechanical stirring. In order to compare catalytic activities, the chiral cobalt salen complexes having $AlCl_3-$, $BF_3-$ and nitrobenzenesulfonic acid (NBSA) were synthesized and used as catalysts, and then three kinds of the racemic epoxides such as ephichlorohydrine (ECH), epoxy phenoxypropane (EPP) and propylene oxide (PO) were used as reactants. In addition, EKR reactions have been performed using the water and methanol as nucleophiles, respectively. The unique contribution of ultrasonic irradiation as a powerful mixing medium was evaluated in this study to improve the kinetics in comparison to the conventional mechanical agitation during EKR reactions. The reaction time to obtain the highest 99 ee% became shorten more than that of above 60%, when the ultrasonic irradiation was used. This result may be interpreted by the cavitation effect of ultrasound in the solution, generating a powerful shear force for the very violent mixing.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.197-197
• /
• 2011

In this study, in contrast with cases in which Scanning Tunneling Microscopy (STM) tip-induced reactions were instigated by the tunneling electrons, the local electric field, or the mechanical force between a tip and a surface, we found that the tungsten oxide (WO3) covered tungsten (W) tip of a STM acted as a chemical catalyst for the S-H dissociative adsorption of phenylthiol and 1-octanethiol onto a Ge(100) surface. By varying the distance between the tip and the surface, the degree of the tip-catalyzed adsorption could be controlled. We have found that the thiol head-group is the critical functional group for this catalysis and the catalytic material is the WO3 layer of the tip. After removing the WO3 layer by field emission treatment, the catalytic activity of the tip has been lost. 3-mercapto isobutyric acid is a chiral bi-functional molecule which has two functional groups, carboxylic acid group and thiol group, at each end. 3-Mercapto Isobutyric Acid adsorbs at Ge(100) surface only through carboxylic acid group at room temperature and this adsorption was enhanced by the tunneling electrons between a STM tip and the surface. Using this enhancement, it is possible to make thiol group-terminated surface where we desire. On the other hand, surprisingly, the WO3 covered W tip of STM was found to act as a chemical catalyst to catalyze the adsorption of 3-mercapto isobutyric acid through thiol group at Ge(100) surface. Using this catalysis, it is possible to make carboxylic acid group-terminated surface where we want. This functional group-selective adsorption of bi-functional molecule using the catalysis may be used in positive lithographic methods to produce semiconductor substrate which is terminated by desired functional groups.

• Journal of the Korean Chemical Society
• /
• v.37 no.1
• /
• pp.119-130
• /
• 1993

The stereochemistry of 1,3-thiazolidine sulfoxides 1 in which 3 chiral centres are present in a molecule was elucidated by deuterium exchange and trapping reactions. 3-Acetoxy-1,3-thiazolidines 5 was oxidized to 6 and 8, corresponding $\alpha$-cis 10, $\alpha$-trans 11, $\beta$ -cis 12, and $\beta$ -trans 13 isomers were separated from their diasteromeric mixtures. Sulfoxide 10 was isomerized to more thermodynamically stable isomer 13 under neutral conditions in refluxing benzene or toluene. The methyl hydrogens of 2-methyl group in the sulfoxide 13 and those of the sulfoxide 11 were deuterated by the deuterium incorporation reactions. The intermediate sulfenic acids 25 and 26 derived from the sulfoxides 10 and 12 via sigmatropic rearrangement were trapped by 2-mercaptobenzothiazole (2-MBT) to give disufides 27 and 28 respectively. However, the sulfoxides 11 and 13 were transformed to ring expansion product dihydro-1,4-thiazine 29 under the same reaction conditions. In the presence of acid catalyst, the sulfoxides 10, 11, and 12 were converted to dihydro-1,4-thiazine 29 through the sulfoxide 13 quantitatively. The mechanisms of isomerization of sulfoxides and the formation of 29 were also discussed.