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Fe(0)촉매를 이용한 Dienyne의 분자내 〔4+2〕고리화 첨가반응에 관한 연구
변상용 釜慶大學校 1998 釜慶大學校 論文集 Vol.3 No.2
The intramolecular formal iron-catalyzed 〔4+2〕 cycloaddition reaction of acetylenic dienes to produce bicyclic products has been investigated. With a typical iron(0) catalyst, prepared by the reduction of Fe(acac)3 with Et3Al in the presence of bipyridine ligand, the (E,E)-4, 4-dicarboethoxy-1-phenyldeca-1-yne-6, 8-diene proceeded competing via intramolecular carbocylization and bimolecular cycloaddition. However, under the similar condition except the chiral ligand, the 4, 4-dimethly〔 -3-(tert-mutyldimethylsiloxy)-1-pheny〕-6, 8-decadien-1-yen yielded exclusively bicyclic diene product(yield 86%).
김에스더,편래현,박지한,김강호,최일,박홍훈,이용희,용태순,홍성관 대한감염학회 2003 감염과 화학요법 Vol.35 No.3
선모충증은 전 세계적으로 발생하는 기생충 인수공통감염의 한로 선모충의 유충에 감염된 육류를 덜 익혀 섭식시 발생하며 감염 초기에 설사, 복통의 증상이 나타나며 후기에 유충의 체내 이행으로 발열, 근염, 안검 부종 등이 동반된다. 확진은 근육 생검을 하여 피포 유충을 확인하는 것이고 최근에는 특이 항체를 측정하거나 유전자 검사와 같은 다양한 검사가 시도되고 있다. 저자 등은 4명의 한 가족이 야생 멧돼지를 생식한 후 선모충증의 전형적인 임상 증상 및 검사 소견을 보인 가족 내 집단발생사례를 경험하였기에 문헌 고찰과 함께 보고하는 바이다. Trichinosis is a worldwide parasitic infection caused by ingesting an uncooked raw meat containing viable larvae of nematode Trichinella. Although most cases have been reported in Western countries, the incidence has decreased due to strict control of meat handlings and improved hygiene in these countries. In Korea, the first case of Trichinella spiralis was reported in a patient who ingested an uncooked badger. We have also experienced four cases of Trichinella spiralis infestation among family members who showed typical clinical manifestations and laboratory findings after ingesting raw wild swine meat, and herein report the finding.
Synthesis and Photopolymerization of Vinyl Ether and Epoxy-Functionalized Silicones
Pyun, Sang-Yong,Kim, Whan-Gi The Polymer Society of Korea 2003 Macromolecular Research Vol.11 No.3
The reactive precursors, vinyl ethers, and epoxy-silicones, were synthesized. The vinyl ether monomers were prepared from primary alcohol and ethyl vinyl ether with mercury (II) acetate. The epoxy-functionalized silicones have been achieved by the controlled, rhodium-catalyzed, chemoselective hydrosilation of vinyl ether with siloxanes or silane. It was shown that the hydrosilation proceeds exclusively at the vinyl ether group of alkenyl vinyl ether without participation at the alkenyl group. The photoinduced cationic polymerization of these monomers was studied and found to be all highly reactive.
Pyun, Sang Yong,Kim, Ju Chang,Cho, Bong Rae Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.7
Ketene-forming elimination from 2-X-4-nitrophenyl furylacetates (1a-d) promoted by $R_2NH-R_2NH_2{^+}$ in 70 mol % MeCN(aq) has been studied kinetically. When X = Cl and $NO_2$, the reactions exhibited second-order kinetics as well as Br$\ddot{o}$nsted ${\beta}$ = 0.37-0.54 and $|{\beta}_{lg}|$ = 0.31-0.45. The Br$\ddot{o}$nsted ${\beta}$ decreased with a poorer leaving group and $|{\beta}_{lg}|$ increased with a weaker base. The results are consistent with an E2 mechanism. When the leaving group was changed to a poorer one [X= H (1a) and $OCH_3$ (1b)], the reaction mechanism changed to the competing E2 and E1cb mechanisms. A further change to the E1cb mechanism was realized for the reaction of 1a with $i-Pr_2NH/i-Pr_2NH_2{^+}$ in 70 mol % MeCN-30 mol % $D_2O$. By comparing the kinetic results in this study with the existing data for $ArCH_2C(O)OC_6H_3-2-X-4-NO_2$, the effect of the ${\beta}$-aryl group on the ketene-forming elimination was assessed.
Pyun, Sang-Yong,Byun, Woong-Sub,Cho, Bong-Rae Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.6
Nitrile-forming eliminations from $(E)-2,4,6-(NO_2)_3C_6H_2CH=NOC_6H_4-2-X-4-NO_2$ (1) promoted by $R_3NH/R_3NH^+$ in 70 mol % MeCN(aq) have been studied kinetically. When X = $NO_2$, the reactions exhibited second-order kinetics as well as Br$\"{o}$nsted ${\beta}$ = 0.63 and ${\mid}{\beta}_{lg}{\mid}$ = 0.34-0.46, and an E2 mechanism is evident. As the leaving group was made poorer (X = H, Cl, and $CF_3$), Br$\"{o}$nsted ${\beta}$ value increased from 0.63 to 0.85-0.89 without much change in the ${\mid}{\beta}_{lg}{\mid}$ value E2, indicating that structure of the transition state changed to an E1cb-like with extensive $C_{\beta}-H$ bond cleavage, significant negative charge development at the ${\beta}$-carbon, and limited $C_{\alpha}$-OAr bond cleavage.
Pyun, Sang-Yong,Cho, Bong-Rae Korean Chemical Society 2005 Bulletin of the Korean Chemical Society Vol.26 No.7
Elimination reactions of $XC_6H_4CH_2CO_2C_6H_3-2-Y-4-NO_2$ have been studied under various conditions. When X was moderately electron-withdrawing, Y = H, and base-solvent was $R_2$NH-MeCN, the reaction proceeded by the E2 mechanism via an E1cb-like transition state. Concave downward curve was noted in the Hammett plots. When X = 4-$NO_2$, Y = Cl, $CF_3,\;NO_2$, and the base-solvent was ${R_2NH/R_2NH_2}^+$ in 70 mol % MeCN(aq), the reaction proceeded by the E2 mechanism. The mechanism changed to a competing E2 and E1cb when X = 4-$NO_2$ and Y = H, MeO, and to the E1cb when X = 2,4-($NO_2)_2$, and Y = $NO_2$. From these results, a plausible pathway of the change of the mechanism from E2 to the E1cb extreme is proposed.
Kinetics Studies on the Mechanism of Hydrolysis of S-Phenyl-S-vinyl-N-p-tosylsulfilimine Derivatives
Pyun, Sang-Yong,Kim, Tae-Rin,Lee, Chong-Ryoul,Kim, Whan-Gi Korean Chemical Society 2003 Bulletin of the Korean Chemical Society Vol.24 No.3
Hydrolysis reactions of S-phenyl-S-vinyl-N-p-tosylsulfilimine (VSI) and its derivatives at various pH have been investigated kinetically. The hydrolysis reactions produced phenylvinylsulfoxide and p-toluene sulfonamide as the products. The reactions are first order and Hammett ρ values for pH 1.0, 6.0, and 11.0 are 0.82, 0.45, and 0.57, respectively. This reaction is not catalyzed by general base. The plot of k vs pH shows that there are three different regions of the rate constants $(k_t)$ in the profile.; At pH < 2 and pH > 10, the rate constants are directly proportional to the concentrations of hydronium and hydroxide ion catalyzed reactions, respectively. The rate constant remains nearly the same at 2 < pH < 10. On the bases of these results, the plausible hydrolysis mechanism and a rate equation have been proposed: At pH < 2.0, the reaction proceeds via the addition of water molecule to sulfur after protonation at the nitrogen atom of the sulfilimine, whereas at pH > 10.0, the reaction proceeds by the addition of hydroxide ion to sulfur directly. In the range of pH 2.0-10.0, the addition of water to sulfur of sulfilimine appears to be the rate controlling step.
Pyun Sang Yong,Paik Kyu Cheol,Han Man So,Cho Bong Rae 대한화학회 2021 Bulletin of the Korean Chemical Society Vol.42 No.7
Reactions of 4-nitrophenyl 2-furoates (1a–e) with R2NH/R2NH2 + in 20 mol% DMSO(aq) have been studied. The reactions produced aminolysis products and exhibited second-order kinetics. The Brönsted plots were linear with βnuc values of 0.75–0.89, which remained nearly the same for all 5-furyl substituents. The rate data showed excellent correlations on the Yukawa-Tsuno plots with ρ(x) = 0.72–1.1, and r = 0.55–0.95, respectively. The ρ value increased and r value decreased with a stronger nucleophile, indicating an increase in the electron density at the C O bond and a decrease in the resonance contribution. The results have been interpreted with the addition–elimination mechanism in which the second step is the rds. By comparing with the data for ArC(O)OC6H4-4-NO2 (Ar = Ph, thienyl), the effect of the aryl group on the acyl transfer reaction was assessed.
Sang Yong Pyun,Eun Ju Cho,Hyoun Jung Seok,Ju Chang Kim,Seok Hee Lee,Bong Rae Cho* 대한화학회 2007 Bulletin of the Korean Chemical Society Vol.28 No.6
Ketene-forming eliminations from C4H3(S)CH2C(O)O-C6H3-2-X-4-NO2 (1) promoted by R2NH in MeCN have been studied kinetically. The reactions are second-order and exhibit Brnsted b = 0.51- 0.62 and |blg| = 0.47-0.53. Hence, an E2 mechanism is evident. The Brnsted b increased from 0.33 to 0.53 and |blg| remained nearly the same by the change of the base-solvent from Bz(i-Pr)NH/Bz(i-Pr)NH2+ in 70mol% MeCN(aq) to Bz(i-Pr)NH-MeCN, indicating a change to a more symmetrical transition state with similar extents of Cb-H and Ca-OAr bond cleavage. When the b-aryl group was changed from thienyl to phenyl in MeCN, the b value increased from 0.53 to 0.73 and |blg| decreased from 0.53 to 0.43. This indicates that the transition state became skewed toward more Cb-H bond breaking with less Ca-OAr bond cleavage. Noteworthy is the greater double bond stabilizing ability of the thienyl group in the ketene-forming transition state.