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He, Maoshuai,Wang, Xiao,Zhang, Lili,Wu, Qianru,Song, Xiaojie,Chernov, Alexander I.,Fedotov, Pavel V.,Obraztsova, Elena D.,Sainio, Jani,Jiang, Hua,Cui, Hongzhi,Ding, Feng,Kauppinen, Esko Elsevier 2018 Carbon Vol.128 No.-
<P><B>Abstract</B></P> <P>The suitability of the NiMgO catalyst as a catalyst in chiral-selective growth of single-walled carbon nanotubes (SWNTs) by chemical vapor deposition has been assessed. It reveals that catalyst calcination temperature plays an important role in affecting the catalyst performances. Using CO as the carbon precursor and a chemical vapor deposition reaction temperature of 600 °C, NiMgO pre-calcined at 600 °C demonstrates the best performances in catalyzing the growth of SWNTs with predominant (6, 5) species. Systematic characterizations on catalysts calcinated at different temperatures indicate that Ni<SUP>2+</SUP> ions diffuse towards the interior of MgO matrix upon annealing. DFT-based calculations reveal that the binding energy between Ni<SUP>2+</SUP> and adjacent Ni(0) is larger than that between Mg<SUP>2+</SUP> and Ni (0), while Ni<SUP>2+</SUP> situated deep inside MgO has weak interactions with surface Ni atoms. This work highlights the importance of subsurface Ni<SUP>2+</SUP> in anchoring reduced surface Ni atom, which inhibits the aggregation of Ni particles and therefore, facilitates the growth of SWNTs with a narrow chirality distribution.</P> <P><B>Graphical abstract</B></P> <P>A Ni-incorporated MgO catalyst was developed for predominant synthesis of (6, 5) single walled carbon nanotubes. Density functional theory-based calculations revealed that the unreduced subsurface Ni stabilized reduced Ni atoms on the surface, facilitating the growth of carbon nanotubes with a narrow chirality distribution.</P> <P>[DISPLAY OMISSION]</P>
카본/메조세공 실리카 복합 막을 응용한 키랄 에폭사이드의가수분해반응과 동시 분리
최성대 ( Seong Dae Choi ),전상권 ( Sang Kwon Jeon ),박근우 ( Geun Woo Park ),양진영 ( Jin Young Yang ),김건중 ( Geon Joong Kim ) 한국공업화학회 2014 공업화학 Vol.25 No.5
The carbon/porous silica composite membrane was fabricated in a simple manner, which could be successfully for the simultaneous separation and production of chiral epoxides and 1,2-diols, based on their differences in hydrophilic/hydrophobic natures. The chiral Co(III)-BF3 salen catalyst adopted in the membrane reactor system has given the very high enantioselectivityand recyclability in hydrolysis of terminal epoxides such as ECH, 1,2-EB, and SO. The optically pure epoxide and the chiral catalyst were collected in the organic phase after hydrolysis reaction. The hydrophilic water-soluble 1,2-diol product hydrolyzed by chiral salen diffused into the aqueous phase through the SBA-16 or NaY/SBA-16 silica composite layer during the reaction. The water acted simultaneously as a reactant and a solvent in the membrane system. One optical isomer was obtained with high purity and yield, and furthermore the catalysts could be recycled without observable loss in their activity in the continuous flow-type membrane reactor.
Park, Jung-Hwan,Shin, Hyun-Ik,Park, Doo-Han,Lee, Sang-Gi Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.3
As a new strategy for the optimization of a chiral catalyst, the catalytic activity of the host-guest complexes of chiral bisphosphine bearing imidazolidinone was investigated in Rh-catalyzed asymmetric hydrogenation of enamide. Marginal enhancement in enantioselectivity was observed and the nature of interaction between host-guest was experimentally elucidated.
Jung Hwan Park,Hyunik Shin,Doo Han Park,이상기 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.3
As a new strategy for the optimization of a chiral catalyst, the catalytic activity of the host-guest complexes of chiral bisphosphine bearing imidazolidinone was investigated in Rh-catalyzed asymmetric hydrogenation of enamide. Marginal enhancement in enantioselectivity was observed and the nature of interaction between host-guest was experimentally elucidated.
Thakur, Santosh Singh,Chen, Shu-Wei,Li, Wenji,Shin, Chang-Kyo,Kim, Seong-Jin,Koo, Yoon-Mo,Kim, Geon-Joong Elsevier 2006 Journal of organometallic chemistry Vol.691 No.9
<P><B>Graphical abstract</B></P><P>Dinuclear chiral salen complexes bearing Lewis acid of group 13 metals catalyze asymmetric ring opening of various terminal epoxides with myriad of nucleophiles via kinetic resolution. The complexes are also found to be active for asymmetric cyclization reaction too.</P><ce:figure></ce:figure> <P><B>Abstract</B></P><P>A new dinuclear chiral Co(salen) complexes bearing group 13 metals have been synthesized and characterized. The easily prepared complexes exhibited very high catalytic reactivity and enantioselectivity for the asymmetric ring opening of epoxides with H<SUB>2</SUB>O, chloride ions and carboxylic acids and consequently provide enantiomerically enriched terminal epoxides (>99% ee). It also catalyzes the asymmetric cyclization of ring opened product, to prepare optically pure terminal epoxides in one step. The homogeneous dinuclear chiral Co(salen) have been covalently immobilized on MCM-41. The potential benefits of heterogenization include facilitation of catalyst separation and recyclability requiring very simple techniques. The system described is very efficient.</P>
Asymmetric Michael Addition of Ketones to Nitroolefins Catalyzed by a New Chiral Catalyst
Lian-Jun Wang,Feng-Feng Hu 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.5
A new chiral catalyst was synthesized and found that it could catalyzed the asymmetric Michael reaction of ketones with nitroolefins smoothly at room temperature, giving the desired adducts in 71 - 92% yields with excellent diastereoselectivities and high enantioselectivities (up to 95% ee).
Asymmetric Michael Addition of Ketones to Nitroolefins Catalyzed by a New Chiral Catalyst
Wang, Lian-Jun,Hu, Feng-Feng Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.5
A new chiral catalyst was synthesized and found that it could catalyzed the asymmetric Michael reaction of ketones with nitroolefins smoothly at room temperature, giving the desired adducts in 71 - 92% yields with excellent diastereoselectivities and high enantioselectivities (up to 95% ee).
초음파 조사에 의한 에폭사이드 비대칭 고리열림 반응의 속도 증진 효과
이예원 ( Yae Won Lee ),박근우 ( Geun Woo Park ),김건중 ( Geon Joong Kim ) 한국공업화학회 2019 공업화학 Vol.30 No.3
본 연구에서는 키랄 코발트 살렌 촉매 존재 하에서 에폭사이드 화합물의 비대칭 고리 열림 반응(EKR)에 미치는 초음파 조사 효과를 기존의 기계적 교반법과 비교하여 고찰하였다. 촉매의 활성을 비교하기 위하여 AlCl3, BF3 및 니트로 벤젠술폰산(NBSA)이 결합된 키랄 코발트 살렌을 합성 사용하였으며, 반응물로는 에피클로로히드린(ECH), 에폭시페녹시프로판(EPP) 및 프로필렌 옥사이드(PO)를 친핵체로는 물과 메탄올을 각각 사용하여 EKR 반응을 수행하였다. 이 반응에서 반응물을 혼합시키는 조작의 일환으로써 초음파를 반응계에 적용한 경우가 통상의 기계적인 교반보다 반응속도를 현저히 증가시키는 결과를 나타내었다. 최고의 거울상 이성체 과잉도 값인 99 ee%를 얻는데 요하는 반응시간은 초음파를 적용하였을 때가 격렬한 물리적 교반을 행한 경우보다 60% 이상 단축되었으며, 이는 용액 중에서 발생하는 초음파의 공동화 현상에 의해 형성된 강한 전단력에 의한 결과로 해석된다. 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 AlCl3-, BF3- 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.