• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2929-2933
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• 2010

Pseudo-first-order rate constants ($k_{obsd}$) have been measured for nucleophilic substitution reactions of 2-pyridyl benzoate 5 with alkali metal ethoxides (EtOM, M = Li, Na, K) in anhydrous ethanol. The plots of $k_{obsd}$ vs. $[EtOM]_o$ are curved upwardly but linear in the excess presence of 18-crown-6-ether (18C6) with significant decreased $k_{obsd}$ values in the reaction with EtOK. The $k_{obsd}$ value for the reaction of 5 with a given EtONa concentration decreases steeply upon addition of 15-crown-5-ether (15C5) to the reaction medium up to ca. [15C5]/$[EtONa]_o$ = 1, and remains nearly constant thereafter, indicating that $M^+$ ions catalyze the reaction in the absence of the complexing agents. Dissection $k_{obsd}$ into $k_{EtO^-}$- and $k_{EtOM}$, i.e., the second-order rate constants for the reaction with the dissociated $EtO^-$ and the ion-paired EtOM, respectively has revealed that ion-paired EtOM is 3.2 - 4.6 times more reactive than dissociated $EtO^-$. It has been concluded that $M^+$ ions increase the electrophilicity of the reaction center through a 6-membered cyclic transition state. This idea has been examined from the corresponding reactions of 4-pyridyl benzoate 6, which cannot form such a 6-membered cyclic transition state.

• Journal of the Korean Applied Science and Technology
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• v.15 no.2
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• pp.49-57
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• 1998

This study is to develop a new synthetic method for the nitroarenes via non-electrophilic substitution. Direct nitration at the C-1 position of isoquinoline has never been reported and substitution in isoquinoline under the normal nitration condition occurs at C-5 and C-8. We have demonstrated a facile one-step sythetic method for the nitration of isoquinolines at the C-1 position, which involves the electrophilic attack of a $DMSO-Ac_2O$ complex, followed by nucleophilic addition of nitrate ion to this intermediate. Since the reaction is simple and mild, this method has preparative merit since 1-nitroisoquinolines are not readily accessible by other methods. Application to the synthesis of poly nitroarenes from the corresponding anilines was also described.

• 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.27 no.12
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• pp.1981-1984
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• 2006

Novel amphiphilic, thermo-responsive polyaspartamides which showed both LCST (lower critical solution temperature), and sol-gel transition were prepared and characterized. The polyaspartamide derivatives were synthesized from polysuccinimide, the polycondensate of aspartic acid monomer, via successive nucleophilic ring-opening reaction by using dodecylamine and N-isopropylethylenediamine (NIPEDA). At the intermediate composition ranges, the dilute aqueous solution exhibited a thermally responsive phase separation due to the presence of LCST. The phase transition temperature was controllable by changing the content of pendent groups. In addition, a physical gelation, i.e. the sol-gel transition was observed from the concentrated solutions, which was elucidated by dynamic viscoelastic measurements. These novel injectable and thermo-responsive hydrogels have potential for various biomedical applications such as tissue engineering and current drug delivery system.

• Applied Chemistry for Engineering
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• v.3 no.1
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• pp.100-110
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• 1992

Arylsulfonyl urea derivatives can be easily prepared in good yield by treating amines with arylsulfonyl carbamates in aqueous solution : 1) N-Arylsulfonyl-N'-aryl urea derivatives, 2) N-Arylsulfony-N'-alkyl urea derivatives, 3) N-Arylsulfonyl-N'- heterocyclic urea derivatives. The proposed reaction mechanisms for preparing arylsulfonyl ureas involve formation of an ion-pair conformation by initial acid-base reaction, then formation of a so-called tetrahedral intermediate by nucleophilic addition, followed by an acid-catalyzed elimination of an alkoxide ion and loss of a proton.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2377-2381
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• 2007

Solvolyses of 3,4-dimethoxybenzenesulfonyl chloride (DSC) in water, D2O, CH3OD, and in aqueous binary mixtures of acetone, acetonitrile, 1,4-dioxane, ethanol, methanol, and 2,2,2-trifluoroethanol (TFE) have been investigated at 25.0 oC. Kinetic solvent isotope effects (KSIE) in water and in methanol and product selectivities in alcohol-water mixtures are also reported. The Grunwald-Winstein plot of first-order rate constants for the solvolyic reaction of DSC with YCl shows marked dispersions into separated lines for various aqueous mixtures. With use of the extended Grunwald-Winstein equation, the l and m values obtained are 1.12 and 0.58 respectively for the solvolyses of DSC. The relatively large magnitude of l is consistent with substantial nucleophilic solvent assistance. From Grunwald-Winstein plots the rate data are dissected approximately into contributions from two competing reaction channels. This interpretation is supported for alcohol-water mixtures by the trends of product selectivities, which show a maximum for ethanol-water mixtures. From the KSIE of 1.45 in methanol, it is proposed that the reaction channel favored in methanolwater mixtures and in all less polar media is general-base catalysed and/or is possibly (but less likely) an addition-elimination pathway. Also, the KISE value of 1.35 for DSC in water is expected for SN2-SN1 processes, with minimal general base catalysis, and this mechanism is proposed for solvolyses in the most polar media.

• Journal of the Korean Chemical Society
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• v.25 no.6
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• pp.390-393
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• 1981

Eight new compounds were prepared by the addition reaction of thioglycolic acid to ${\beta}$-nitrostyrene and its derivatives. s-[2-Nitro-1-phenylethyl]-thioglycolic acid; s-[2-nitro-1-(p-methyl)phenylethyl]-thioglycolic acid; s-[2-nitro-1-(p-methoxy)phenylethyl]-thioglycolic acid; s-[2-nitro-1-(p-chloro)phenylethyl]-thioglycolic acid; s-[2-nitro-1-(p-bromo)phenylethyl]-thioglycolic acid; s-[2-nitro-1-(p-nitro)phenylethyl]-thioglycolic acid; s-[2-nitro-1-(3-methoxy-4-ethoxy)phenylethyl]-thioglycolic acid; s-[2-nitro-1-(3,4,5-trimethoxy)phenylethyl]-thioglycolic acid; The structure of these compound were identified by elemental analysis, UV, IR and NMR spectral data.

• Journal of the Korean Chemical Society
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• v.35 no.3
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• pp.258-261
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• 1991

Four thiazolidines and following five new compounds were prepared by the addition reaction of cysteine and thiophenol to ${\alpha}$,N-diphenylnitrones, respectively ; ${\alpha}$,thiophenoxy-benzylidene aniline ;${\alpha}$,thiophenoxy-p-hydroxybenzylidene aniline ; ${\alpha}$,thiophenoxy-p-chlorobenzylidene aniline ;${\alpha}$,thiophenoxy-p-methoxybenzylidene aniline ; ${\alpha}$,thiophenoxy-p-nitrobenzylidene aniline. The structure of these compounds were confirmed by the elemental analysis, UV-, IR-and NMR-spectra.

• Journal of the Korean Chemical Society
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• v.33 no.1
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• pp.120-126
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• 1989

The Kinetics of hydrolysis of styrylphenylsulfone derivatives in 50% methanol-water at 25$^{\circ}$C and ionic strength of 0.10 was investigated by UV spectrophotometry in the pH range of 0.0-14.0. The rate equations, which can be applied over a wide pH range, were obtained. The Hammett rho constants for the hydrolysis are 1.85 at pH 7.0 and 1.54 at pH 13.0, respectively. On the basis of the evidence, it is proposed that the general base-catalysis occurs in the hydrolysis of styrylphenylsulfone derivatives; above pH 11.0, Michael type nucleophilic addition take place, while below pH 9.0, the reaction is initiated by addition of water and from pH 9.0 to pH 11.0 these two reactions occur com-petitively.

• Journal of the Korean Applied Science and Technology
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• v.29 no.3
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• pp.429-434
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• 2012

A kind of Antihistamines, Azelastine HCl which known as modern H1-blockers, was synthesized by four step process using phthalic anhydride, 4-chlorophenylacetic acid, hydrazine 2HCl. The first step was the reaction of removing carboxyl group and hydroxyl group and the second step was saponification of 3-(4-chlorobenzylidene)phthalide. The third step was the nucleophilic addition reactions of primary amines and the fourth step was addition reaction of N-methyl-1-aza-bicyclo[3,2,0]heptane to 4-(4-chlorobenzyl)-1-(2H)phthalazinone. As a result, product was analyzed by FT-IR and $^1H$-NMR and could be obtained with a yield of 80%.