• Macromolecular Research
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• 제10권2호
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• pp.91-96
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• 2002

To explore the effects of intramolecular interactions within the copolymer on the phase separation behavior of polymer blends, copolymers having two different types of intramolecular interactions, i.e., intramolecular repulsion and intramolecular attraction were prepared . In this study, poly(styrene-co-methylmethacrylate) (P(S-MMA)) having intramolecular repulsion caused by positive interaction between styrene and MMA and poly(styrene-co-ethyl-methacrylate) (P(S-EMA)) and poly(styrene-co-cyclohexylmethacrylate) (P(S-CHMA)) having intramolecular attraction caused by negative interaction between styrene and methacrylate were blended with tetramethyl poly-carbonate (TMPC). The phase behavior of blends was examined as a function of copolymer composition and blend composition. TMPC formed miscible blends with styrenic copolymers containing less than certain amount of methacrylate. The phase separation temperature of TMPC blends with copolymer such as P(S-MMA) and P(S-EMA), first increases with methacrylate content, goes through a maximum and then decreases just prior to the limiting content of methacrylate for miscibility, while that of TMPC blends with P(S-CHMA) always decreases. The calculated interaction energy for TMPC-P(S-EMA) pair is negative and monotonically increases with EMA content of the copolymer. Such behavior contradicted the general notion that systems with more favorable energetic interactions have higher LCST, The detailed inspection of the lattice-fluid theory related to the phase behavior was performed to explain such behavior.

• Bulletin of the Korean Chemical Society
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• 제28권7호
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• pp.1127-1134
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• 2007

It was demonstrated that Y[N(TMS)2]3, the neutral yttrium-diamine complex 13 and yttrium-NPS complexes 15 are efficient precatalysts for intramolecular hydroamination of aminoalkynes involving primary amines. Complex 13 and 15 were quantitatively prepared in situ by direct metalation of the ligands 4 and 9 with 1 equiv of Y[N(TMS)2]3 in benzene-d6 at 120 oC for 5 days and 10 days, respectively, via elimination of (TMS)2NH. 5-Exo- and 6-exo-dig intramolecular hydroamination of aminoalkynes using catalyst 12 and 13 proceeded smoothly to give nitrogen-contained cyclic products in good to excellent yields in all cases. In the case of 7- exo-dig intramolecular hydroamination, the desired product was produced in 41% and 48% yields despite the gem-dimethyl effect. However, treatment of catalyst 15 with aminoalkynes (19 and 22) having a methyl substituent at the carbon adjacent to triple bond and 6-exo-dig intramolecular hydroamination of 21 failed to give the desired products. Zirconium-catalyzed intramolecular hydroamination of aminoallenes (25, 27, and 31) with 5 mol% 16 afforded 2-(trans-1-propenyl)pyrrolidine, 2-isopropylenepyrrolidine, and 2-(trans-1- propenyl)piperidine in 96%, 95%, and 93% yield, respectively. However, subjecting 25 to 5 mol% 15 was unsuccessful to produce the desired product.

• 미생물학회지
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• 제34권4호
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• pp.231-235
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• 1998

Escherichia coli 세포에서 intramolecular triplex가 형성될 수 있는지를 조사하기 위하여 genetic assay를 도입하였다. Two dimensional gel electrophoresis 방법을 사용하여 $(G)_9AATTC(G)_9$ 혹은 $(GAA)_9TTC(GAA)_8$ sequences가 in vitro에서 intramolecular triplex 구조를 형성하는 것을 확인하였다. Genetic assay를 위하여 temperature-sensitive EcoRI methylase 유전자를 포함한 플라스미드와 triplex를 형성할 수 있는 $(G)_9AATTC(G)_9$ 혹은 $(GAA)_9TTC(GAA)_8$ sequences를 포함한 플라스미드로 E. coli를 cotransform 하였다. EcoRI methylase가 발현되는 permissive temperature에서 pur pyr sequences를 포함하는 플라스미드는 EcoRI methylase 작용에 kinetically 저항성을 보여주었다. 이러한 결과는 pur pyr sequence들이 EcoRI methylase가 작용하기 어려운 triplex 구조를 E. coli 세포에서 형성한다는 것을 증거한다.

• Bulletin of the Korean Chemical Society
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• 제24권7호
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• pp.916-920
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• 2003

Photoreactions of N-(2,4-dibromonaphthyl)arenecarboxamides in basic medium result in the intramolecular substituted products, 2-aryl-8-bromonaphthoxazoles in moderate yields and further photoreactions of the products afford the reduced products, 2-arylnaphthoxazoles. These reactions are straightforward for syntheses of naphthoxazole derivatives. Since the intramolecular photosubstitution of the bromoarenecarboxamide by the oxygen of its amide group is more effective than the photoreduction of the substituted product, 2-aryl-8- bromonaphthoxazole in basic medium, the intramolecular substituted product, 2-aryl-8-bromonaphthoxazole can be isolated. A charge-transfered excited singlet state of an imidol form of the 2-bromoarenecarboxamide is involved in the photosubstitution, whereas an excited triplet state of the 2-aryl-8-bromonaphthoxzole is closely involved in the photoreduction.

• Bulletin of the Korean Chemical Society
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• 제23권9호
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• pp.1208-1254
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• 2002

Photoreaction of N-(o-halophenyl)acetamide in basic acetonitrile produces an intramolecular substituted product, 2-methylbenzoxazole in addition to reduced product, acetanilide, whereas photoreaction of N-(o-halobenzyl) acetamide affords a reduced product, N-benzylacetamide only. On the basis of preparative reaction, kinetics, and UV/vis absorption behavior, an electrophilic aromatic substitution of aryl halide with oxygen of its amide bond are proposed.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.35-36
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• 2006

Excited-state intramolecular proton transfer (ESIPT) is a phototautomerization occurring in the excited states of the molecules possessing a cyclic intramolecular or solvent-bridged hydrogen bond. Recently, we have developed novel ESIPT chromophores, molecules, dendrimers and polymers which show very high fluorescence quantum efficiency combined with the characteristic features of optical switching, fluorescence patterining, lasing, and electroluminescence. Broad overview of these topics will be given in this talk.

• Bulletin of the Korean Chemical Society
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• 제31권9호
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• pp.2527-2530
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• 2010

The stereoselectivity of the intramolecular Diels-Alder reactions of 1 and its derivatives were investigated by ab initio calculations. The stereoselectivity mainly originates from the steric repulsion and the orbital interactions. The additional s-cis and s-trans conformations by introducing the carbonyl group at the neighbor of diene or dienophile may change the stereoselectivity, hence this kind of substitution can be utilized for stereoselectivive asymmetric synthesis.

• 약학회지
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• 제41권6호
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• pp.714-717
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• 1997

Stereoselective synthesis of the optically active bicyclo [4.2.0] octanone 5 was accomplished using intramolecular olefin-keteniminium salt[2+2]cycloaddition of the amide 4 as a key step. This important chiral synthon was prepared starting from readily available L-glutamic acid via an efficient 8-step sequence.

• Bulletin of the Korean Chemical Society
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• 제15권6호
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• pp.448-452
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• 1994

2-Hydroxymethyl-2,5-dihydrothiophene 1,1-dioxide (1) was prepared from thiophene-2-carboxylic acid by consecutive reactions involving the Birch reduction, esterification, reduction with lithium aluminum hydride, and oxidation with Oxone$^{\circledR}$. The esterification of alcohol 1 with various unsaturated carboxylic acids provided the precursors 8 for the intramolecular Diels-Alder reaction. The cheletropic expulsion of sulfur dioxide from the esters 8 followed by intramolecular Diels-Alder reaction furnished bicyclic ${\gamma}$-and ${\delta}$-lactones.

• Bulletin of the Korean Chemical Society
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• 제17권2호
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• pp.158-162
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• 1996

The steady-state emission and fluorescence lifetimes of 1,3-dipyrenylpropane were measured in silicate sol-gel and xerogel matrices. In sol solution, the fluorescence emission spectra of monomer and excimer resemble those in hydrocarbon solvents. In gel and xerogel condition, however, the fluorescence spectra exhibit significant change, largely confirming the intramolecular motions in gel pores are influenced by microviscosity. The rate constants for intramolecular excimer formation were obtained from the measured fluorescence lifetimes and the rate processes for excimer forming in silicate sol-gel are described by a simple kinetic scheme.