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Gold-Catalyzed Cyanosilylation Reaction: Homogeneous and Heterogeneous Pathways
Cho, Woo ,Kyung,Lee, Jungkyux2005,K.,Kang, Sungx2005,Min,Chi, Young Shik,Lee, Hee-Seung,Choi, Insungx2005,S. Wiley - VCH Verlag GmbH & Co. KGaA 2007 Chemistry Vol.13 No.22
<P>Gold had been considered to be an extremely inert metal, but recently it was found that nanometer-sized gold particles on metal-oxide supports acted as catalysts for simple organic reactions, such as oxidation and hydrogenation, even at or below room temperature. Herein, we report that gold nanoparticles (AuNPs) of zero oxidation state (Au<SUP>0</SUP>) are catalytically active for a C&n.bond;C bond-forming reaction, the cyanosilylation of aldehydes. The AuNP-catalyzed cyanosilylation proceeded smoothly at room temperature with 0.2 wt % loading of AuNPs. The reactions of aromatic aldehydes were almost quantitative, except for benzaldehyde derivatives containing the electron-withdrawing NO<SUB>2</SUB> group, and α,β-unsaturated aromatic aldehydes were the most reactive substrates. The reactions also went smoothly for aliphatic aldehydes. Mechanistic studies indicated that the reactions proceeded both homogeneously and heterogeneously: homogeneous catalysis by leached gold species and heterogeneous catalysis by the adsorption of the reactants (aldehydes and trimethylsilyl cyanide) onto AuNPs. The ratio of homogeneous and heterogeneous catalysis was estimated to be ≈4:1.</P> <B>Graphic Abstract</B> <P>Good as gold: Gold nanoparticles (AuNPs) were found to be catalytically active for a C&n.bond;C bond-forming reaction, the cyanosilylation of aldehydes. The AuNP-catalyzed cyanosilylation proceeded smoothly at room temperature with 0.2 wt % loading of AuNPs (see scheme; TMS: trimethylsilyl). Detailed experiments indicate that the reaction occurs by a combined pathway of heterogeneous and homogeneous catalysis. <img src='wiley_img/09476539-2007-13-22-CHEM200601791-content.gif' alt='wiley_img/09476539-2007-13-22-CHEM200601791-content'> </P>
Two New <i>C</i>‐<i>seco</i> Limonoids from the Fruit of <i>Melia azedarach</i>
Jin, Qinghao,Lee, Chul,Woo ,Lee, Jin,Yeonx2005,Choi, Jeong,Taex2005,Hong, Jin,Kim, Youngsoo,Kyeongx2005,Lee, Mi,Yeonx2005,Hwang, Bang WILEY‐VCH Verlag 2014 Helvetica chimica acta Vol.97 No.8
<P><B>Abstract</B></P><P>A phytochemical investigation of the fruits of <I>Melia azedarach</I> led to the isolation of two new C‐<I>seco</I>‐nimbolinin‐type limonoids, 3<I>α</I>‐acetoxy‐1<I>α</I>,7<I>α</I>‐dihydroxy‐12<I>α</I>‐methoxynimbolinin (<B>1</B>) and 3<I>α</I>‐acetoxy‐1<I>α</I>,12<I>α</I>‐dihydroxy‐7<I>α</I>‐(2‐methylprop‐2‐enoyl)nimbolinin (<B>2</B>), together with eleven known compounds, <B>3</B>–<B>13</B>. Their structures were elucidated on the basis of extensive spectroscopic analysis, including <SUP>1</SUP>H‐ and <SUP>13</SUP>C‐NMR, HMQC, HMBC, NOESY, and HR‐FAB‐MS.</P>
Separation of Olefin/Paraffin Mixtures Using Zwitterionic Silver Complexes as Transport Carriers
Kim, Hoonx2005,Sik,Bae, Jinx2005,Yong,Park, Sangx2005,Joon,Lee, Hyunjoo,Bae, Hyunx2005,Woo,Kang, Sangx2005,Ook,Lee, Sangx2005,Deuk,Choi, Daix2005,Ki WILEY-VCH Verlag 2007 Chemistry Vol.13 No.9
<P>Zwitterionic silver nitrate salts of 1-(1-methyl-3-imidazolio)propane-3-sulfonate, 1-(1-methyl-1-pyrrolidinio)propane-3-sulfonate, and 1-(4-methyl-4-morpholio)propane-3-sulfonate have been prepared and tested as carriers for facilitated olefin transport membranes in the separation of ethylene/ethane, propylene/propane, and C<SUB>4</SUB> mixtures. The interactions of olefins with silver ions bound to sulfonate groups were investigated by FTIR spectroscopy as well as the correlation between the binding affinity of olefins and facilitated transport.</P> <B>Graphic Abstract</B> <P>Various imidazolium-, pyrrolidinium- and morpholinium-based zwitterionic silver complexes have been prepared and their performances as carriers for facilitated transport composite membranes investigated for selective separation of ethylene/ethane, propylene/propane, and C<SUB>4</SUB> mixtures (see picture). <img src='wiley_img/09476539-2007-13-9-CHEM200600869-content.gif' alt='wiley_img/09476539-2007-13-9-CHEM200600869-content'> </P>
Hwang, Ilha,Jeon, Woo ,Sung,Kim, Hee-Joon,Kim, Dongwoo,Kim, Hyunuk,Selvapalam, Narayanan,Fujita, Norifumi,Shinkai, Seiji,Kim, Kimoon WILEY-VCH Verlag 2007 Angewandte Chemie Vol.46 No.1
<B>Graphic Abstract</B> <P>Without modification of its periphery, cucurbit[7]uril (a macrocyclic cavitand comprising seven glycoluril units) forms a hydrogel. The gelation is thermoreversible and sensitive to pH, but is inhibited by the presence of alkali-metal ions and shows guest-induced stimuli-responsive behavior: upon addition of a small amount of a guest, it undergoes a reversible gel–sol transition with alternating UV irradiation and heat treatment (see picture). <img src='wiley_img/14337851-2007-46-1-2-ANIE200603149-content.gif' alt='wiley_img/14337851-2007-46-1-2-ANIE200603149-content'> </P>
Maiti, Kaustabhx2005,K.,Lee, Woo ,Sirl,Takeuchi, Toshihide,Watkins, Catherine,Fretz, Marjan,Kim, Dong-Chan,Futaki, Shiroh,Jones, Arwyn,Kim, Kyong-Tai,Chung, Sung-Kee WILEY-VCH Verlag 2007 Angewandte Chemie. international edition Vol.46 No.31
<B>Graphic Abstract</B> <P>Special delivery: Transporters constructed on a sorbitol scaffold with eight guanidine residues show significant translocation across the cell membrane and the blood–brain barrier and high affinities toward mitochondria in HeLa and KG1a leukemia cells. The picture shows colocalisation of one such transporter (T) with MitoTracker red in KG1a cells (scale bars: 10 μm). <img src='wiley_img/14337851-2007-46-31-ANIE200701346-content.gif' alt='wiley_img/14337851-2007-46-31-ANIE200701346-content'> </P>