• Bulletin of the Korean Chemical Society
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• v.34 no.4
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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.

• Bulletin of the Korean Chemical Society
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• v.27 no.8
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• pp.1099-1114
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• 2006

Our studies in the area of single electron transfer (SET) photochemistry have led to the discovery of efficient processes, in which regioselective formation of carbon-centered radicals takes place by nucleophile assisted desilylation of $\alpha$-trialkylsilyl substituted ether, thioether, amine and amide centered cation radicals. The rates of bimolecular desilylation of the intermediate cation radicals exceed those of other cation radical $\alpha$-fragmentation processes (e.g.,-deprotonation). This sereves as the basis for the design of highly regioselective, SET-induced photomacrocyclization reactions of polyether, polythioether, polyamide, and polypeptide linked phthalimides. Photocyclization reactions of trimethylsilyl-terminated substrates in these families are unique in that they produce polyfunctionalized macrocyclic substances in a highly efficient and regioselective manner. In addition, our studies in this area have led to important information about the factors that govern chemical and quantum efficiencies that should be applicable to a wide variety of redox processes promoted by SET from substrates containing more than one electron donor site.

• Bulletin of the Korean Chemical Society
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• v.16 no.11
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• pp.1056-1059
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• 1995

The bulk photopolymerization of methyl methacrylate (MMA) with primary arylsilane (e.g., phenylsilane) and various primary alkylsilanes (e.g., benzylsilane, 3-phenoxyphenyl-1-silabutane, 3-naphthyl-1-silabutane, and 3-chlorophenyl-1-silabutane) was performed to produce poly(MMA)s containing the corresponding silyl moiety as an end group. It was found for the phenylsilane that while the polymerization yields increased and then decreased with a turning point at the molar ratio of MMA:silane=10:1 as the relative silane concentration increases, the polymer molecular weights decreased, and the TGA residue yields and the relative intensities of SiH IR stretching bands increased with increment of molar ratio of silane over MMA. The photopolymerization yield of MMA with the arylsilane was found to be higher than those with the alkylsilanes and without the silanes. Thus, the silanes seemed to significantly influence on the photopolymerization as both chain initiation and chain transfer agents.

• Bulletin of the Korean Chemical Society
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• v.22 no.12
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• pp.1337-1340
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• 2001

The bulk photopolymerization of methyl methacrylate (MMA) with para-substituted phenylsilanes such as F-C6H4SiH3 (1), H3C-C6H4SiH3 (2), and H3CO-C6H4SiH3 (3) was performed to produce poly(MMA)s containing the respective silyl moiety as an end group. For all the hydrosilanes, the polymerization yields and the polymer molecular weights decreased, whereas the TGA residue yields and the relative intensities of Si-H IR stretching bands increased as the relative silane concentration over MMA increased. The polymerization yields and polymer molecular weights of MMA with 1-3 increased in the order of 3 < 1 < 2. These hydrosilanes influence significantly upon the photopolymerization of MMA as both chain-initiation and chain-transfer agents.

• Bulletin of the Korean Chemical Society
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• v.17 no.6
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• pp.532-535
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• 1996

The bulk photopolymerization of methacrylic acid (MA) with secondary silanes such as PhMeSiH2 and Ph2SiH2 gave poly(MA)s possessing the secondary silyl moiety presumably as an end group. It was found that while the polymerization yields and intrinsic viscosities decreased, the TGA residue yields and the relative intensities of SiH IR stretching bands increased with increasing mole ratio of the secondary silane over MA. The sterically less bulky silane PhMeSiH2 produced poly(MA)s with somewhat higher molecular weights and with similar TGA residue yields compared with the sterically bulkier silane Ph2SiH2. The secondary silanes seem to significantly influence on the photopolymerization of MA as both chain initiation and chain transfer agents.

• Bulletin of the Korean Chemical Society
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• v.21 no.3
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• pp.291-294
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• 2000

The bulk photopolymerization of methyl methacrylate(MMA) with bis(silane)s such as 1,4-$C_6H_4(SiH_3)_2$ (1) and 1,4-$C_6H_4(SiH_2Me)_2$ (2) was performed to produce poly(MMA)s possessing the corresponding bis(silyl) moiety as an end group. For the bis(silane)s, while the polymerizaiton yields and the polymer molecular weights decreased, the TGA residue yields and the relative intensities of Si-H IR stretching bands increased as the relative bis(silane) concentration over MMA increased. The polymerizaion yield, polymer molecular weight, and TGA residue yield of MMA with 1 were found to be higher than those with 2. The bis(silane)s appears to influence significantly upon the photopolymerization of MMA as both chain initiation and chain transfer agents.

• Bulletin of the Korean Chemical Society
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• v.13 no.2
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• pp.166-172
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• 1992

Studies have been conducted to explore single electron transfer (SET) induced photocyclization reactions of N-(trimethylsilylmethoxyalkyl)phthalimides(alkyl=E thyl, n-propyl, n-butyl, n-pentyl, and n-octyl). Photocyclizations occur in methanol in high yields to produce cyclized products in which phthalimide carbonyl carbon is bonded to the carbon of side chain in place of the trimethylsilyl group. Mechanism for these photocyclizations involving intramolecular SET from oxygen in the $\alpha-silylmethoxy$ groups to the singlet excited state phthalimide moieties followed by desilylation of the intermediate $\alpha-silylmethoxy$ cation radicals and cyclization by radical coupling are proposed. In contrast, photoreaction of N-(trimethylsilylmethoxyethyl) phthalimide in acetone follows different reaction routes to produce two cyclized products in which carbon-carbon bond formation takes place between the phthalimide carbonyl carbon and the carbon $\alpha$ to silicon and oxygen atoms via triplet carbonyl hydrogen abstraction triplet carbonyl silyl group abstraction pathways. The normal singlet SET pathway dominates these triplet processes for photoreaction of this substance in methanol. The efficient and regioselective cyclization reactions observed for photolysis in methanol represent synthetically useful processes for construction of medium and large ring heterocyclic compounds.

• Journal of the Korean Chemical Society
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• v.24 no.3
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• pp.250-258
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• 1980

Various radicals may add to isonitriles to give imidoyl radcals RN=CR'. This may be also generated via abstraction of imidoyl hydrogen from imine in the following manner: RN=CR' ＋ R"${\cdot}{\rightarrow}$ RN=CR' ＋ R"-H Imidoyl radicals would be stabilized via two pathways, ${\beta}$-cleavage and atom transfer reactions. ${\beta}$-Cleavage may occur in two directions depending upon structure of the radicals. Cyanide transfer and the "so-called" normal ${\beta}$-cleavage are the two modes of ${\beta}$-cleavage. Addition of t-butoxy radical to t-butyl isocyanide 7 generates an imidoyl radical t-Bu-N=C-O-Bu-t, which undergoes ${\beta}$-cleavage to give t-butyl isocyanate and t-butyl radical. Addition of phenyl radical to 7 forms the intermediate radical t-Bu-N=$C-C_6H_5$, which decomposes to give benzonitrile and t-butyl radical. The t-butyl radical generated from the ${\beta}$-cleavage adds to 7 giving the radical t-Bu-N=C-Bu-t, which cleaves only to pivalonitrile and t-butyl radical, inducing radical chain isomerization. Trimethylsilyl radical adds to 7 to give the intermediate t-Bu-N=$C-Si(CH_3)_3$, which collapses to $(CH_3)_3$SiCN and a t-butyl radical.