• 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.

• 한국환경과학회지
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• 제26권7호
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• pp.859-868
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• 2017

In this study, the reductive dechlorination of triclosan using zero-valent iron (ZVI, $Fe^0$) and modified zero-valent iron (i.e., acid-washed iron (Aw/Fe) and palladium-coated iron (Pd/Fe)) was experimentally investigated, and the reduction characteristics were evaluated by analyzing the reaction kinetics. Triclosan could be reductively decomposed using zero-valent iron. The degradation rates of triclosan were about 50% and 67% when $Fe^0$ and Aw/Fe were used as reductants, respectively, after 8 h of reaction. For the Pd/Fe system, the degradation rate was about 57% after 1 h of reaction. Thus, Pd/Fe exhibited remarkable performance in the reductive degradation of triclosan. Several dechlorinated intermediates were predicted by GC-MS spectrum, and 2-phenoxyphenol was detected as the by-product of the decomposition reaction of triclosan, indicating that reductive dechlorination occurred continuously. As the reaction proceeded, the pH of the solution increased steadily; the pH increase for the Pd/Fe system was smaller than that for the $Fe^0$ and Aw/Fe system. Further, zero-order, first-order, and second-order kinetic models were used to analyze the reaction kinetics. The first-order kinetic model was found to be the best with good correlation for the $Fe^0$ and Aw/Fe system. However, for the Pd/Fe system, the experimental data were evaluated to be well fitted to the second-order kinetic model. The reaction rate constants (k) were in the order of Pd/Fe > Aw/Fe > $Fe^0$, with the rate constant of Pd/Fe being much higher than that of the other two reductants.

• 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.

• Journal of Biosystems Engineering
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• 제33권3호
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• pp.210-215
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• 2008

The objective of this study was to develop models to predict SCC (somatic cell count) in unhomogenized milk by visible and near-infrared (NIR) spectroscopic technique. Total of 100 milk samples were collected from dairy farms and preserved to minimize propagation of bacteria cells during transportation. Reductive reagents such as methyl red, methylene blue, bromcresol purple, phenol red and resazurin were added to milk samples, and then colors of milk were changed based on SCC of milk. For optimal reductive reagents, reaction time was controlled at 3 level of reaction time. A spectrophotometer was used to measure reflectance spectra from milk samples. The partial least square (PLS) models were developed to predict SCC of unhomogenized milk. The PLS results showed that milk samples with reductive reagents had a good correlation between predicted and measured SCC at 5 minutes of reaction time in the visible range. The PLS models with resazurin reagent had the best performance in $400{\sim}600\;nm$. The prediction results of milk samples with resazurin had 0.86 of correlation coefficient and 14,184 cell/mL of SEP.

• 약학회지
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• 제41권4호
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• pp.480-483
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• 1997

The efficient synthesis of p-(acetylamino)phenylacetic acid(7), a antirheumatic agent, is reported. Methyl phenylacetate(3) was prepared from Friedel- Crafts reaction of benzene with methyl ${\alpha}$-chloro-${\alpha}$-(methylthio)acetate(1) followed by reductive desulfurization with zinc dust in acetic acid. Compound(7) was obtained from 3 by a sequence of nitration, reduction, N-acylation, and hydrolysis.

• 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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• 제33권1호
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• pp.333-336
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• 2012

• Bulletin of the Korean Chemical Society
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• 제31권3호
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• pp.582-587
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• 2010

A rhodium-catalyzed reductive cleavage reaction of carbon-cyano bonds is developed using hydrosilane as a mild reducing agent. A wide range of nitriles, including aryl, benzyl, and $\beta$-hydrogen containing alkyl cyanides are applicable to this decyanation reaction. The method is also applicable to organic synthesis, in which benzyl cyanide is used as a benzyl anion equivalent and a cyano group functions as a removable ortho-directing group.

• Archives of Pharmacal Research
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• 제17권3호
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• pp.190-193
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• 1994

Friedel-Crafts reaction isopropoxybenzene with methyl $\alpha$-chloro-$\alpha$-(maethylthio)acetate 1 afforded methyl $\alpha$-methylthio-p-isopropoxyphenylacetate 2d, which was readily converted into methyl p-isopropoxyphenylacetate 3 by reductive desulfurization with zinc dust in acetic acid. Methylation of 3 with sodium hydride and methyl iodide gave methyl $\alpha$-(p-isopropoxyphenyl)propionate 5. Methyl p-hydroxyphenylakanoates (4,6), useful intermediates for some medicines, were easily prepared by treatment of 3 and 5 with titanium tetrachloride, respectively.

• 대한화학회지
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• 제27권3호
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• pp.194-200
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• 1983

${\alpha}-Fe_2O_3$의 HCl 또는 $H_2SO_4$에 의한 용해반응에 있어서 금속염의 첨가효과를 분광광도법과 중량법으로 검토하였다. 환원성 금속염은 현저한 반응촉진 효과를 보이나 비환원성 금속염은 부의 효과를 나타내었다. $FeCl_2$와 같은 환원성 금속염을 첨가한 경우에 ${\alpha}-Fe_2O_3$의 용해속도가 크게 촉진되는 것은 $Fe^{3+}$ 와 $Fe^{2+}$ 사이에 chloro-brige가 형성되어 전하이동이 일어나면서 ${\alpha}-Fe_2O_3$ 표면의 격자에너지를 감소시키기 때문인 것으로 추측된다. 이 전하이동으로 인한 ${\alpha}-Fe_2O_3$ 표면의 격자 에너지 변화가 반응의 활성화에너지 변화와 대응된다고 보면 약 0.36e의 부분전하가 $Fe^{3+}$ 쪽으로 옮겨간 것으로 계산되었다.