Kwang Ho Song

Synthesis of symmetrical and unsymmetrical diarylalkynes from propiolic acid using palladium-catalyzed decarboxylative coupling.

Symmetrical diarylalkynes were obtained from propiolic acid (or 2-butynedioic acid) and aryl halides in good yields. The optimized reaction conditions were 2.0 equiv of aryl halide, 1.0 equiv of propiolic acid, 5.0 mol % Pd(PPh(3))(2)Cl(2), 10.0 mol % 1,4-bis(diphenylphosphino)butane (dppb), 2.0 equiv of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and dimethyl sulfoxide (DMSO) as the solvent. The coupling reaction of 2-butynedioic acid with aryl halides required 110 °C. The coupling reaction showed tolerance for functional groups such as ester, ketone, and aldehyde and exhibited chemoselectivity. In the coupling reaction of propiolic acid with aryl bromide, the diarylated product was the major one at 80 °C, even though 1 equiv of aryl halides was employed. However, among the monoarylated products that were formed predominantly at 25 and 50 °C in the coupling reaction with aryl iodide, more Sonogashira coupling product was obtained than the decarboxylative coupling product. Unsymmetrical diarylalkynes were also synthesized via this method, in which all reagents, including propiolic acid, aryl iodide, and aryl bromides were added at the beginning of the reaction.

The scope and limitation of nickel-catalyzed aminocarbonylation of aryl bromides from formamide derivatives.

Nickel-catalyzed aminocarbonylation of aryl halides is described. A well-defined air-stable nickel-phosphite catalytic system (Ni(OAc)(2).4H(2)O/phosphite 1) effectively promoted the aminocarbonylation of aryl bromides with a range of formamides to give the corresponding aryl amide products in moderate to good yields. The less hindered formamide required lower catalytic loading for full conversion and produced higher yields than the more hindered one. It also exhibited base-dependent activity toward formamides.

Palladium-Catalyzed Decarboxylative Trifluoroethylation of Aryl Alkynyl Carboxylic Acids

A trifluoroethylation of alkynes through a palladium-catalyzed decarboxylative coupling reaction was developed. When alkynyl carboxylic acids and ICH2CF3 were allowed to react with [Pd(η(3)-allyl)Cl]2/XantPhos and Cs2CO3 in N,N-dimethylformamide (DMF) at 80 °C for 1 h, the desired products were formed in good yields. This catalytic system showed high functional group tolerance.

Development of a 600 W Proton Exchange Membrane Fuel Cell Power System for the Hazardous Mission Robot

Due to the advantage of fuel cells over secondary batteries such as long operation time, many efforts were executed in order to use fuel cells as main power sources of small electronic devices such as laptop computers and mobile phones. For the same reason, fuel cells are promising power sources for the hazardous mission robots. Fuel cells are able to increase their radius action through extension of operation time. Despite this advantage, there still exist technical barriers such as increasing power density, efficient hydrogen storage, and fast startup of the power system. First, in order to increase power density the united stack including proton exchange membrane fuel cells (PEMFC) and membrane humidifying cells were developed. Also, the hydrogen generating system using NaBH 4 solution was employed to store hydrogen effectively. In addition, to shorten start-up time, hybrid control of PEMFC and Li-ion battery was adopted. The approaches mentioned above were evaluated. The developed PEMFC/humidifier stack showed high performance. As compared with full humidification condition by external humidifiers, the performance decrease was only 1% even though hydrogen was not humidified and air was partially humidified. Besides, by integrating the PEMFC and the humidifier into a single stack, considerable space for tubing between them was saved. Also, the hydrogen generator operated well with the PEMFC system and allowed for effective fuel storing and refueling. In addition, due to the efficient hybrid control of PEMFC and battery, start-up time was significantly shortened and capacity of PEMFC was reduced, resulting in compactness of the power system. In conclusion, a 600 W PEMFC power system was developed and successfully operated with the robot. Through development and evaluation of the PEMFC power system, the possibility of PEMFC as a novel power source for the hazardous mission robot was verified.

Enhanced production of cellobiose dehydrogenase and β-glucosidase by Phanerochaete chrysosporium

The production of cellobiose dehydrogenase (CDH) and β-glucosidase by Phanerochaete chrysosporium ATCC 32629 was assessed during submerged fermentation. The maximum concentrations of CDH and β-glucosidase were obtained using rice straw as the carbon source. Organic nitrogen sources were more effective in enzyme production than inorganic nitrogen sources. Corn steep liquor (CSL) for CDH production and soy bean meal (SBM) for β-glucosidase production were the most appropriate organic nitrogen sources. Using optimum medium obtained by response surface methodology (RSM), the maximum concentrations of CDH and β-glucosidase achieved in the stirred-tank reactor (STR) were 204 U/L and 140 U/L, respectively. CDH productivity (22.7 U/L·day) was the highest at 9 days.

Influence of process parameters on ethylene-norbornene copolymers made by using [2,2′-methylenebis(1,3-dimethylcyclopentadienyl)]-zirconium dichloride and MAO

Ethylene-norbornene copolymerization was investigated by using metallocene catalysts, [2,2′-methylenebis( 1,3-dimethylcyclopentadienyl)]zirconium dichloride(2,2′-CH2 (1,3-Me2Cp)2ZrCl2, Catalyst A) and racemicethylenebis( indenly)zirconium dichloride (rac-Et(Ind)2 ZrCl2, Catalyst B), in the presence of methylaluminoxane as a cocatalyst. The influences of different process parameters such as polymerization temperature and ethylene pressure were studied by using a 56 wt% norbornene solution in toluene. The results show that Catalyst A has a higher activity in copolymerization than Catalyst B. Catalyst A also has a superior norbornene insertion performance to Catalyst B, resulting in polymers with higher glass transition temperatures, by approximately 70 ‡C, at similar polymerization conditions, indicative of a great commercial potential of Catalyst A.

Micromixer as a Continuous Flow Reactor for the Synthesis of a Pharmaceutical Intermediate

A mixing device composed of a micron scale flow channel was applied as a continuous reactor to control exothermic reaction heat and to increase the product yield, in a synthesis of a pharmaceutical intermediate of quinolone antibiotics. The model reaction featured a fast reaction rate, high heat generation, and impurity formation due to a prolonged contact time between reactants and products. Using the micromixer reactor, the reaction heat was efficiently removed so that virtually no impurities were produced during the reaction. A product yield comparable to the theoretical value was achieved in a single micromixer unit. Optimum operating conditions were acquired from a statistical method by using factorial design, which was also verified by a CFD calculation.

Efficient Immobilization Technique for Enhancement of Cellobiose Dehydrogenase Activity on Silica Gel

In this study, cellobiose dehydrogenase (CDH) of Phanerochaete chrysosporium ATCC 32629 was immobilized on silica gel for the further application of CDH in the saccharification process of biomass. To prevent the loss of enzyme activity during enzyme immobilization, the pretreatment of CDH was performed by various pretreatment materials before immobilization. When pretreated enzymes were used in immobilization, the activities of immobilized CDH were higher than non-pretreated CDH even in same amounts of immobilized protein. The specific activity of pretreated immobilized CDH with lactose was about two times higher than that of non-pretreated immobilized CDH. Moreover, the pretreated immobilized CDH showed better reusability than non-pretreated immobilized CDH, with 67.3% of its original activity being retained after 9 reuses.

Heat Transfer Effect of Inert Gas on Multi-Tubular Reactor for Partial Oxidation Reaction

The heat transfer effect of an inert gas on a multi-tubular reactor for a partial oxidation reaction has been determined. The model reaction system in the study was partial oxidation of propylene to acrolein. Both theoretical modeling and experimental studies have been performed to determine the heat transfer effect of inert gas on the system. Among many inert gases, CO2 was selected and tested as a diluent gas for the partial oxidation of propylene to acrolein system instead of conventionally used N2. The productivity increase through changing the inert gas from N2 to CO2 was possible due to the heat transfer capability of CO2. In this study, by replacing the inert gas from N2 to CO2, productivity increased up to 14%.

Alternating magnetic field mediated micro reaction system for palladium-catalyzed coupling reactions

A continuous flow reaction system in which a palladium magnetic catalyst was immobilized and vibrated by an alternating induced magnetic field was developed. The alternating electromagnetic field improved the mixing efficiency and catalytic activity for the palladium-catalyzed coupling reactions. This flow reaction system showed good product yields for various reactions such as Sonogashira, Heck, Suzuki, Stille, Hiyama and decarboxylative coupling reactions.