• Journal of the Korean Chemical Society
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• v.23 no.5
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• pp.325-328
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• 1979

trans-1,2-Bispyrazylethylene (BPE) undergoes photoaddition reaction to tetramthylethylene (TME) which appears to involve radical intermediates under conditions where the corresponding hydrocarbons are unreactive. This photoaddition reaction involves abstraction of an allylic hydrogen atom of TME by $^1(n,\;{\pi}^*)$ states of BPE having radical character. The major photoadduct is isolated by column chromatography and fractional vacuum sublimation and characterized to be 2,3-dimetyl-5,6-bispyrazyl-2-hexene.

• Journal of Photoscience
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• v.9 no.1
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• pp.17-22
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• 2002

Studies have been conducted to explore photoaddition reactions of N-methylthiophthalimide with $\alpha$-silyl-n-electron donors Et$_2$NCH$_2$SiMe$_3$, n-PrSCH$_2$SiMe$_3$ and EtOCH$_2$SiMe$_3$. Photoaddition of $\alpha$-silyl amine Et$_2$NCH$_2$SiMe$_3$ to N-methylthiophthalimide occurs in $CH_3$CN and benzene to produce non-silicon containing adduct in which thiophthalimide thione carbon is bonded to $\alpha$-carbon of $\alpha$-silyl amine in place of the trimethylsilyl group. In contrast, photoaddition of EtOCH$_2$SiMe$_3$ to N-methylthiophthalimide generates two diastereomeric adducts in which thiophthalimide thione carbon is connected to $\alpha$-carbon of $\alpha$-silyl ether in place of u-hydrogen. Based on a consideration of the oxidation potentials of u-silyl-n-electron donors and the nature of photoadducts, mechanism for these photoadditions involving single electron transfer(SET) -desilylation and H atom abstraction pathways are proposed.

• Bulletin of the Korean Chemical Society
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• v.13 no.6
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• pp.654-658
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• 1992

Photolysis of 1-phenyl-1,3,5-hexatriynes in deaerated tetrahydrofuran gave photoreduction and photoaddition products, while photolysis of 1-phenyl-1,3,5-hexatriynes in deaerated alcoholic solvents (methanol, i-propanol) yielded dark red products, probably oligomers or decomposition products of reactants, as exclusive major products. A plausible mechanism for the reaction is proposed.

• Rapid Communication in Photoscience
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• v.2 no.3
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• pp.76-78
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• 2013

Photoaddition reactions of aromatic carbonyl compounds with silyl thioketene acetals have been explored. The results of this study show that the acetonphenone react with dimethyl substituted silyl thioketene acetal competitively via either single electron transfer (SET)-desilylation or [2+2]-cycloaddition pathways to produce b-hydroxyester and oxetanes. In contrast, photochemical reactions of the benzaldehyde with dimethyl substituted silyl thioketene acetal mainly lead to the formation of oxetanes arising by [2+2] cycloaddition. A comparison of the results with those of silyl ketene acetal revealed that replacement of sulfur atom in ${\alpha}$-silyl donor substrate bring about dramatic changes in chemoselectivities as well as excited state reaction mechanism.

• Bulletin of the Korean Chemical Society
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• v.28 no.4
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• pp.629-634
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• 2007

Photochemical reactions of N-methylphthalimide with silyl enol ethers have been explored. Irradiations of phthalimide (1) and cyclic silyl enol ethers (5a-b) are observed to promote formation of photoreduced phthalimides and photoaddition products by sequential SET-desilylation pathways. The photoreaction of phthalimide (1) and acyclic silyl enol ethers (5c-d) leads to produce oxetanes which arise by competitive single electron transfer (SET) and classical 2+2 photocycloaddition (Parteno-Buchi reaction) pathways.

• Bulletin of the Korean Chemical Society
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• v.10 no.3
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• pp.223-226
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• 1989

The chemical reactivity of 5,7-dimethoxycoumarine with adenosine has been calculated by the frontier electron and PPP-Cl MO methods. Results suggest that the major reactivity of the 5,7-dimethoxycoumarin is highest at the carbon-4 (position 4), whereas the electrophilic reactivity is generally spread all over the 5,7-dimethoxycoumarin molecule. These results are consistent with the experimental photoaddition reaction products. The small change of bond orders on excitation does not give enough reactivity to triplet states or the efficient intersystem crossing from $T_1\;to\;S_0$ inhibits photoaddition of 5,7-dimethoxycoumarine to adenosine. Although the relative intensity of the singlet band appears to be considerably higher than the triplet band intensity, its integrated intensity, i.e. oscillator strength, is comparable to that of the 5,7-dimethoxycoumarin and adenosine bands.

• Bulletin of the Korean Chemical Society
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• v.7 no.3
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• pp.228-230
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• 1986

Diacetylene compound, 1,4-diphenyl-1,3-butadiyne, was photolyzed with 5-fluorouracil as a model reaction of the phototoxic conjugated poly-ynes with DNA or RNA and obtained a [2 + 2] photocycloadduct. The structure of the photoadduct was determined by spectral methods and compared with the [2 + 2] photoadducts of 1,4-diphenyl-1,3-butadiyne with tetramethylethylene and dimethyl fumarate.

• Bulletin of the Korean Chemical Society
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• v.23 no.9
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• pp.1218-1242
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• 2002

Photochemical reactions of aromatic carbonyl compounds with silyl ketene acetals have been explored. Irradiation of acetonitrile or benzene solutions containing aryl aldehydes or ketones in the presence of silyl ketene acetals is observed to promo te formation of ${\beta}-hydroxyester$, 2,2-dioxyoxetane and 3,3-dioxyoxetane products. The ratios of these photoproducts, which arise by competitive single electron transfer (SET) and classical Paterno-Buchi mechanistic pathways, is found to be dependent on the degree of methyl-substitution on the vinyl moieties of the ketene acetals in a manner which reflects expected alkyl substituent effects on the oxidation potentials of these electron rich donors. An analysis of the product distribution arising by irradiation of a solution containing butyrophenone (6) and the silyl ketene acetal 9, derived from methyl isobutyrate, provides an estimate of the rate constants for the competitive Norrish type Ⅱ, SET and Paterno-Buchi processes occuring. Finally, sequences involving silyl ketene acetal-aryl aldehyde or ketone photoaddition followed by 2,2-dioxyoxetane hydrolysis represent useful procedures for Claisen-condensation type, ${\beta}-hydroxyester$ synthesis.

• Bulletin of the Korean Chemical Society
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• v.8 no.3
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• pp.206-211
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• 1987

The photoreaction of 5,7-dimethoxycoumarin with adenosine has been carried out in a dry film state. The mixture of DMC and adenosine was irradiated with 350 nm UV light and two major products were isolated. The structure was determined by various spectroscopic measurements involving $^{13}C$ nuclear magnetic resonance and fast atom bombardment mass spectrometry. These addition products were produced by covalent bond formation between the pyrone ring at carbon 3 or 4 and the sugar ring moiety of adenosine at carbon 5'.

• Bulletin of the Korean Chemical Society
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• v.10 no.1
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• pp.57-60
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• 1989

UV irradiation of anthraquinone and diphenylacetylene in benzene gave 1:1 photoadduct (7) and cyclization product (8). The photoreaction of anthrone and diphenylacetylene in dichloromethane afforded the photooxidation products (7, 8, and 9) in air. The photoproduct (7) underwent the cyclization reaction during the purification by the column chromatography (silica gel). When irradiated with 350 nm UV light, the product (11) of benzil reacted with diphenylacetylene to give a photoadduct(12).