• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3372-3376
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• 2013

The kinetic studies on the reactions of ethyl methyl (2) and ethyl propyl (4) chlorothiophosphates with X-pyridines have been carried out in acetonitrile at $35.0^{\circ}C$. The free energy correlations with X show biphasic concave upwards with a break point at X = H (2) and 3-Ph (4), respectively. A stepwise mechanism with a rate-limiting leaving group expulsion from the intermediate is proposed based on the magnitudes of selectivity parameters for both substrates. The considerably large values of ${\beta}_X$ = 1.50(2) and 1.44(4) with strongly basic pyridines and relatively small values of ${\beta}_X$ = 0.43(2) and 0.36(4) with weakly basic pyridines are interpreted as a change of the attacking direction of the X-pyridines from a frontside to a backside attack toward the chloride leaving group.

• Bulletin of the Korean Chemical Society
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• v.29 no.5
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• pp.1018-1024
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• 2008

Photolysis of 2-(pentamethyldisilanyloxy)phenylpentamethyldisilane 1 in methanol provides five photoproducts 3, 4, 5, 6, and 7. Compounds 3 and 4 were probably formed from the methanol addition reactions of silene intermediate 2 and the formation of 5, 6, and 7 can best be explained by the nucleophilic attack of methanol to silicon atom in pentamethyldisilanyloxy or pentamethyldisilanyl group of the photoexcited state of 1. Irradiation of 1 in n-hexane gives a photoproduct 6 via silyl radical intermediate 8 and a novel intramolecular cyclization photoproduct 11 via silene 9 and silyl radical intermediate 10. Irradiation of 1 in deaerated methylene chloride in the presence of acetone affords a novel photoproduct 11 and phenol 7 but the expected photoproducts from the reaction of the silene intermediate with acetone were not obtained.

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1096-1100
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• 2013

The kinetic studies on the reactions of O-methyl (1), O-propyl (3) and O-isopropyl (4) phenyl phosphonochloridothioates with substituted anilines and deuterated anilines have been carried out in acetonitrile at $55.0^{\circ}C$. A concerted $S_N2$ mechanism is proposed for the anilinolyses of 1, 3 and 4. The anilinolysis rates of the phosphonochloridothioates are predominantly dependent upon the steric effects over the inductive effects of the two ligands. The deuterium kinetic isotope effects (DKIEs; $k_H/k_D$) are primary normal with 1 and 3, while secondary inverse with 4. Primary normal and secondary inverse DKIEs are rationalized by frontside and backside nucleophilic attack transition state, respectively. The DKIEs of the phosphonochloridothioates do not have any consistent correlations with the two ligands.

• Journal of the Korean Chemical Society
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• v.20 no.4
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• pp.295-298
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• 1976

The fact that a reaction between organothioenamine phosphonate and styrene oxide produces a derivative of cyclopropane has been proved by structural identification. This suggests that an anionic oxygen atom from the ring opening of the styrene oxide by nucleophilic attack of thioenamine phosphonate links to the phosphorous atom to from a betaine as an intermediate which is followed by cleavage of the weak P-C bond. The dextrorotatory optical activity of the product showed that the reaction was under the control of steric stability of the benzyl carbon in styrene which leads to the product through a sterically stable pathway.

• Bulletin of the Korean Chemical Society
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• v.30 no.6
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• pp.1331-1336
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• 2009

Photolysis of (2-hydroxyethoxyphenyl)pentamethyldisilane 2 in benzene provides a novel intramolecular cyclization photoproduct 9 which was probably formed from the intramolecular reaction to form a seven-membered ring in silatriene intermediate 7 and then the photochemical disrotatory ring closure of 1,3-butadiene moiety to cyclobutene. Irradiation of 2 in methanol afforded photoproducts 5 and 6 which were formed by the nucleophilic attack of methanol to $\beta$ or $\alpha$ silicon atom in pentamethyldisilanyl group of the photoexcited state of 2. Compounds 10 and 11 were also formed by the same way as in the formation of the photoproducts 5 and 6 in the photolysis of (2-allyloxyethoxyphenyl)pentamethyldisilane 3 in methanol solvent. Photoreaction of (2-acetoxyethoxyphenyl) pentamethyldisilane 4 in methanol gave a photoproduct 12 which was formed via the elimination of dimethylsilylene species in the photoexcited state of 4.

• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.1016-1022
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• 2014

The kinetic studies on the reactions of O-methyl N,N-diisopropylamino phosphonochloridothioate with X-anilines and X-pyridines have been carried out in acetonitrile. The free energy relationship with X in the anilines exhibits biphasic concave upwards with a break region between X = (H and 4-F), giving unusual negative ${\beta}_X$ and positive ${\rho}_X$ values with weakly basic anilines. The unusual phenomenon is rationalized by isokinetic relationship. A stepwise mechanism with a rate-limiting leaving group departure from the intermediate is proposed based on the selectivity parameter and variation trend of the deuterium kinetic isotope effects with X. The free energy relationship with X in the pyridines exhibits biphasic concave upwards with a break point at X = 3-MeO. A concerted mechanism is proposed based on relatively small ${\beta}_X$ value, and frontside and backside nucleophilic attack are proposed with strongly and weakly basic pyridines, respectively.

• Bulletin of the Korean Chemical Society
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• v.17 no.1
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• pp.29-33
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• 1996

Mono-, or di-substituted chlorodicyanovinyl benzene compound was reacted with an excess amount of ethylenediamine to give corresponding imidazoline product with high reaction yield. This reaction occurs by stable imidazoline ring-forming process through nucleophilic attack of terminal amine on the enaminonitrile adduct, the reaction intermediate, toward electropositive enamine carbon, which is accompanied by the release of neutral malononitrile moiety. The similar reaction with 1,2-phenylenediamine produced stable enaminonitrile-amine adduct at lower temperature which could be cyclized intramolecularly to thermally stable benzimidazole at elevated temperature in solution or in solid state. From the difunctional compound of both reactants, poly(enaminonitrile-amine) could be prepared as a new soluble precursor polymer for well-known polybenzimidazole (PBI). The thermal cyclization reaction accompanying the release of malononitrile molecules was studied using thermalanalysis and infrared spectroscopy.

• Bulletin of the Korean Chemical Society
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• v.12 no.1
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• pp.75-79
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• 1991

A series of compounds, N-(2-substituted-1-carboxy)vinylazetidinones were successfully synthesized in order to test the hypothesis that biological activities of ${\beta}$-lactam antibiotics could be attributed to the smooth flow of electrons after a nucleophilic attack at the carbonyl carbon in the ${\beta}$-lactam ring. After introduction of aminothiazolylacetamido group at 3-position of the azetidinones, their biological activities were evaluated. Their low activities led to the conclusion that the smooth electron flow in ${\beta}$-lactams in not the sufficient source for the biological activities.

• Bulletin of the Korean Chemical Society
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• v.1 no.3
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• pp.83-87
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• 1980

The Murrell-Fueno type of the intermolecular perturbation approach was applied to the acid-catalyzed hydrolysis of diformamide. The results show that: (1) the attack of a water molecule on the protonated carbonyl carbon is favored over that on the unprotonated carbonyl carbon; (2) the ${\sigma}$-approach model of water is preferred to the ${\pi}$-approach model; (3) the major contributing term to the total energy is the Coulomb energy, $E_q$, especially in the ${\sigma}$-approach, while the contribution of $E_{ct}$ (and $E_k$) increases moderately in the ${\pi}$-approach; (4) the reaction is a charge-controlled one, a hard-hard type in the language of the HSAB principle.

• Bulletin of the Korean Chemical Society
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• v.15 no.9
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• pp.729-732
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• 1994

The acid-promoted cleavage of the E-and Z-isomers of 1-phenyl-6-neopentyl-1,3,4-trimethyl-1-silacyclohe x-3-ene(II) under various conditions gave clean and nearly quantitative formation of the ring-opened 2,3,7,7-tetramethyl-5-(X)silyl-1-octene products (X=OMe, Cl, OH). The possible mechanism for the formation of the ring-opened products was suggested that the initial protonation of II at C-4 would give a carbocation oriented so that they are ${\beta}$ to the silicon atom, and the subsequent nucleophilic attack at silicon would give rise to the observed products (VI, VII, VIII).