• Bulletin of the Korean Chemical Society
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• 제32권11호
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• pp.3973-3978
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• 2011

The reductive pinacol coupling reaction of aldehydes or ketones creating a new C-C bond has been a major tool to produce 1,2-diol compounds. The reaction mechanism is known to be composed of sequential three steps (activation, coupling, and dissociation). In this work, we studied the dissociation step of half-titanocene-based catalytic systems. Cp and $Cp^*$ derivatives of the pinacolato-bridged dinuclear complex were synthesized and evaluated as possible models for intermediates from the coupling step. We monitored $^1H$-NMR spectra of the reaction between the metalla-pinacol intermediates and $D_2O$. New reaction routes of the dissociation step including oxo- and pinacolato-dibridged dinuclear complexes and oxo-bridged multinuclear complexes have been suggested.

• 전기화학회지
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• 제2권4호
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• pp.209-212
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• 1999

H-형의 분리 셀을 사용하여 중성 및 실온의 온화한 조건에서 조절 전위법 음전극 반응에 의한 nitroarene화합물들의 환원 짝지음 반응으로 높은 수율의 azobenzene유도체를 합성하였다. Pb또는 Pt cathode와 Pt anode를 사용하여 메탄을 용액 하에서 cyclic voltammetry에 근거하여 각 반응의 최적의 반응 조건을 결정한 후 반응을 실행하였으며, 대부분의 경우 환원 짝지음 반응은 치환기의 성질과 위치에 영향을 받지 않고 높은 수율로 성공적인 결과를 얻을 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제30권2호
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• pp.327-333
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• 2009

For the Pt-catalyzed nucleophilic addition of enones, Pt complexes were employed in the presence of various phosphine ligands and $H_2\;(or\;Et_3SiH),$ affording inter- and intra-molecular coupling products in good to modest yield. Depending on reaction protocols, different phosphine ligands were required to optimize the conditions. In the aldol reaction, the Pt catalyst involving $P(2,4,6-(OMe)_3C_6H_2)3\;or\;P(p-OMeC_6H_4)_3$ was chosen. Michael reaction proceeds in good yields in the presence of $P(p-CF_3C_6H_4)_3$. Regarding the activity of the reductants, $H_2$ exhibited superior activity to $Et_3SiH$, resulting in a shorter reaction time and higher yield in the aldol and Michael reaction. In light of the deuterium labeling studies, the catalytic cycle including the hydrometalation of the enones by the platinum hydride species was proposed.

• Bulletin of the Korean Chemical Society
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• 제31권2호
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• pp.500-502
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• 2010

• 대한화학회지
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• 제40권1호
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• pp.96-99
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• 1996

• Bulletin of the Korean Chemical Society
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• 제27권11호
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• pp.1839-1843
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• 2006

Hydrothermal reactions of $Ln(NO_3)_3{\cdot}5H_2O $ (Ln = Eu (1), Sm (2), Ho (3), Dy (4)) with 3,5-pyridinedicarboxylic acid (3,5-pdcH2) in the presence of 4,4'-bipyridine led to the formation of the 3-D Ln(III)-coordination polymers with a formula unit of $[Ln_2(3,5-pdc)_2(C_2O_4)(H_2O)_4]{\cdot}2H_2O$. These polymers contain a bridging oxalate ligand ($C_2O_4\;^2$). On the basis of GCMS study of the mother liquor remaining after the reaction, we proposed that the $C_2O_4\;^2$ formation proceeds in three steps: (1) Ln(III)-mediated decarboxylation of $3,5-pdcH_2$ to give $CO_2$, (2) the reduction of $CO_2$ to $CO_2\;^{\cdot}$ by the Ln(II) species, and (3) the reductive coupling of the two $CO_2\;^{\cdot}$ radicals to the oxalate ($C_2O_4\;^2$) ion. All polymers were structurally characterized by X-ray diffraction.

• 폴리머
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• 제31권6호
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• pp.469-473
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• 2007

본 연구에서는 OTFT의 유기물 반도체 층으로 쓰일 수 있는 oligo(3-methylthiothiophene)를 전이금속 촉매인 palladium 촉매를 이용한 커플링 중합법을 이용하여 합성하였다. Thiophene 올리고머의 단량체를 합성하기 위해서 metal halogen exchange reaction에 의하여 3-methylthiothiophene를 합성하였고, thiophene 구조의 2, 5번의 위치에 brome기를 도입함으로써 최종적으로 2,5-dibromo-3-methylthiothiophene를 합성하였다. 합성된 단량체와 올리고머는 $^1H-NMR$, ATR 분석을 통하여 그 구조를 확인하였으며, TGA로 열적 안정성을 관찰하였고 진공 증착법(thermal evaporation)을 이용하여 기판상에 증착시켜 OTFT 소재로서의 적용 가능성을 확인하였다.

• Journal of Microbiology and Biotechnology
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• 제13권4호
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• pp.501-508
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• 2003

Artificial coupling of one enzyme with another can provide an efficient means for the production of industrially important chemicals. Xylose reductase has been recently discovered to be useful in the reductive production of xylitol. However, a limitation of its in vitro or in vivo use is the regeneration of the cofactor NAD(P)H in the enzyme activity. In the present study, an efficient process for the production of xylitol from D-xylose was established by coupling two enzymes. A NADH-dependent xylose reductase (XR) from Pichia stipitis catalyzed the reduction of xylose with a stoichiometric consumption of NADH, and the resulting cofactor $NAD^+$ was continuously re-reduced by formate dehydrogenase (FDH) for regeneration. Using simple kinetic analyses as tools for process optimization, suitable conditions for the performance and yield of the coupled reaction were established. The optimal reaction temperature and pH were determined to be about $30^{\circ}C$ and 7.0, respectively. Formate, as a substrate of FDH, affected the yield and cofactor regeneration, and was, therefore, adjusted to a concentration of 20 mM. When the total activity of FDH was about 1.8-fold higher than that of XR, the performance was better than that by any other activity ratios. As expected, there were no distinct differences in the conversion yields of reactions, when supplied with the oxidized form $NAD^+$ instead of the reduced form NADH, as a starting cofactor for regeneration. Under these conditions, a complete conversion (>99%) could be readily obtained from a small-scale batch reaction.

• 대한화학회지
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• 제37권1호
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• pp.136-140
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• 1993

새로운 methotrexate 중간체인 diethyl N-[4-{[(2,4-diamino-6-yl)methyl]-amino}benzoyl]-L-glutamate(10)를 합성하기 위하여 p-nitrobenzoic acid를 chlorination한 다음 L-glutamic acid와 coupling하고 이를 esterification한 후, 환원과 methylation시켜 diethyl N-(4-methylaminobenzoyl)-L-glutamate(7)를 합성하였다. 이 화합물(7)을 DMF 존재하에서 NaH와 allyl chloride를 가하여 allylation한 다음 여기에 $IN_3$ addition 반응으로 diethyl-p-[N-(2-azido-3-iodopropyl)-N-methyl]aminobenzoyl-L-glutamate(9)를 합성하였다. 이 화합물(9)을 2,4,5,6-tetraaminopyrimidine hydrochloride와 cyclization시켜 methotrexate diethylester를 얻었다.

• Archives of Pharmacal Research
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• 제25권1호
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• pp.49-52
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• 2002

Syntheses of ($\pm$)-homoepibatidine analogues (2), which contain the 8-azabicyclo [3.2.1 ]octane ring system, were achieved by using palladium-catalyzed reductive-coupling reaction from 3 and the analgesic activity was tested by Mouse writhing antinociceptive assay