• Journal of Photoscience
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• 제3권2호
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• pp.91-93
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• 1996

In connection with our interest on the photochemical properties of heteroaryl halides, which are currently the subject of heterocyclic ring formation and haloarene degradation, we have studied the photochemistry of the haloarene linked to N-heteroarene compounds. Imidazo[5,1-a]isoindole was synthesized from N-(ochlorobenzyl)imidazole or N-(o-bromobenzyl) imidazole in acidic aqueous solution or acetonitrile via the intramolgcular photocyclization (Table 1). This type of reaction provides the synthetic methods for 5- and 6-membered polyheteroatomic heterocyclic ring compounds. However, the reaction mechanism for the intramolecular photocyclization of haloarene tethered heteroarenes has not yet been established. Grimshaw et al. suggested a mechanism for homolyric carbonhalogen bond fission assisted by radical complexation to explain their results in the photocyclization of 5-(2-chlorophenyl)-1,3-diphenylpyrazole. They also reported the detection of acyclohexadienyl intermediate involved in the above reaction. Park et al. reported several transient 'intermediates involved in the laser flash photolysis of N-(o-halobenzyl) pyridinium and N-benzyl-2-halopyridinium salts. Thus we performed the laser flash photolysis study on the photocyclization reaction of N-(o-chlorobenzyl) imidazole to identify the intermediate species involved in the reaction. Here, we report on the preliminary results in the photocyclization reaction of N-(o-halobenzyl)imidazole through the detection of reaction intermediates.

• 대한화학회지
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• 제20권3호
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• pp.212-220
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• 1976

1,1'-디시클로알케닐의 광고리화 반응을 형광 퀘ㄴ칭, 증감제등을 써서 연구하였다. 증감제를 쓰는 경우 이 디엔의 광고리화 반응은 비틀린 삼중상태나 평면구조의 트란스 삼중상태보다 높은 에너지 준위에 있는 평면구조의 s-시스 삼중상태에서 일어남을 알았다.

• Bulletin of the Korean Chemical Society
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• 제32권9호
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• pp.3465-3468
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• 2011

• Journal of Photoscience
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• 제10권1호
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• pp.49-60
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• 2003

How stereo selectivity in singlet and triplet photocycloaddition and photocyclization reactions, respectively, is linked to spin selectivity and how this link affects our understanding of photochemical reaction mechanisms, is described in this review. As illustrative examples, the Paterno-Buchi reaction and the Norrish-Yang cyclization are described with emphasis on triplet biradical structure and dynamics.

• Bulletin of the Korean Chemical Society
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• 제14권1호
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• pp.152-153
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• 1993

• 대한화학회지
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• 제29권4호
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• pp.426-436
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• 1985

몇가지 벤즈아닐리드류를 합성하여 광반응시킨 후 생성물을 분리하고 그 구조를 결정하였다. 벤즈아닐리드 자체는 광고리화 안되고 Photo-Fries형 생성물을 주었지만 2-chlorobenzaniline, 2-bromobenzanilide, 및 2-methoxybenzanilide는 질소기류하에서 광고리화하여 모두 phenanthridone을 생성하였다. 2-chloro-2-nitrobenzanilide는 광고리화되지 않았다. 니트로기가 페닐고리에 도입되니 들뜬상태의 에너지가 낮아서 광고리화 안되었다. 2,2'-dichlorobenzanilide가 광고리화 되어 8-chlorophenanthridone이 되는 것으로 보아 들뜬 부분은 카르보닐쪽의 페닐 부분인것을 알 수 있었다. 2'-위치에 Cl이 있는 경우에도 광고리화 되었다. 2-chlorobenzanilide나 2'-chlorobenzanilide에 대하여 몇가지 용매중에서 광고리화 양자수득률을 구하였는데, 2-chlorobenzaniline는 효과적으로, 2'-chlorobenzanilide는 비효과적으로 광고리화 되었다. 대체로 비극성용매중에서 또 저점성용매중에서 양자수득률이 좋았다. 2-chlorobenzaniline가 광고리화 될때 산소의 영향을 시험하였는데, 산소가 존재하는 데서 광고리화가 잘 안되었다. 따라서 이때 삼중상태가 상관하는 것을 알았으며 전이상태는 염소원자가 떨어져 나가고 이때 이웃 페닐고리가 도우는 메카니즘을 제안한다. 삼중상태의 2-chlorobenzaniline에서 카르보닐쪽의 페닐과 N-페닐의 도움으로 카르보닐쪽의 페닐에 붙은 염소원자 떨어져나가 중간체인 컨쥬게이션된 라디칼이 된다. 이 라디칼에서 수소원자가 떨어져 나가 phenanthridone이 되는데, 이 단계는 속도결정단계가 아니다. 왜냐하면, 이 광고리화 반응에서 수소대신 중수소를 치환해도 속도에는 영향이 없기 때문이다. 2-methoxybenzanilide가 광고리화 될때는 산소가 존재하니 반응이 빨라졌다. 이는 단일 상태가 상관하는 것 같으며 산소가 중간체를 산화하여 반응을 촉진하는 것 같다.

• Bulletin of the Korean Chemical Society
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• 제34권4호
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• pp.1108-1114
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• 2013

Photochemical reactions of fluoro- vs. nonfluoro-substituted polymethylenoxy chain linked phthalimide were carried out to explore how electronegative fluorine atoms inside the donor chain influence photocyclization reaction efficiencies and to briefly determine the alkali metal binding properties of the photoproducts. The results of this study show that the fluorine-substituted donor chain linked phthalimide undergoes inefficient photocyclization via single electron transfer (SET)-induced excited state pathways to generate 14-membered cyclic amidol compared to nonfluoro-analog due to low electron donor ability of the terminal oxygen donor site. These results show that photoinduced intramolecular SET processes arising from ${\alpha}$-silyl ether electron donors to phthalimides are largely dependent on the kinds of substituents inside donor chain. Finally, a preliminary study with the cyclic amidols generated in this effort showed that they have weak alkali metal cation binding properties regardless of absence/presence of fluoro-substituents.

• Journal of Photoscience
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• 제6권2호
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• pp.67-70
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• 1999

trans-1-(9-Anthryl)-2-(n-pyridyl)ethene (t-n-APyE, n=2 or 4) and trans-1-(9-anthryl)-2-pyrazinylethene (T-APzE) exhibits solvent-dependent fluorescence and efficient trans)cis photoisomerization. Photochemical reactivities of t-2-APyE, t-4-APyE, and t-APzE have been investigated in nonpolar and polar solvents. In nonpolar solvent, parallel photocyclization reaction occurs very efficiently in competition with the fluorescence and photoisomerization. But, in polar solvent, photocyclization was not observed. It is probably due to the stabilization of charge separated state in polar solvent, which is an intermediate in photoisomerization reaction.

• Bulletin of the Korean Chemical Society
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• 제1권2호
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• pp.68-70
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• 1980

1,4,5,8-Tetraazaphenanthrene, a new tetraazaheteroaromatic compound, has been synthesized photochemically in 90 % yield and quantum yield of $5.1{\times}10^{-2}$ from dilute benzene solutions of 1,2-bispyrazyl ethylene(BPE) in the presence of oxygen as an oxidant. Iodine was not appropriate oxidant because of strong complexing with BPE and also enhanced intersystem crossing of BPE and thereby decreasing the photocyclization of BPE. Salt effect, solvent effect, and quenching and sensitization studies on the photocyclization of BPE have shown that ($^l(n, {\pi}^*$) is the reactive state for the cyclization in comparison to ($^1{\pi}, {\pi}^*$) state for the ordinary stilbene derivatives.

• Journal of Photoscience
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• 제12권2호
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• pp.83-85
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• 2005

Photochemical reactivities of ${\beta}-ethoxypropiophenones$ are changed dramatically by putting a halogen at a position to the carbonyl functionality. ${\alpha}-Bromo-{\beta}-ethoxypropiophenone$ gives C-Br bond cleavage products solely, but ${\alpha}-chloro-{\beta}-ethoxypropiophenone$ forms mainly the Yang photocyclization products upon irradiation. The different reactivities of two compounds can be explained by relative rates of C-X bond cleavage and a-hydrogen abstraction.