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Photocyclization of 1,2-Bispyrazylethylene and 2-Styrylpyrazine
Sang-Chul Shim,Suk-Kyu Lee Korean Chemical Society 1980 Bulletin of the Korean Chemical Society Vol.1 No.2
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.
Photochemical Behavior of Limettin
Sang Chul Shim 한국생약학회 1980 생약학회지 Vol.11 No.3
C₄-Photocycloaddition reactions of limettin, a naturally occurring photodynamic coumarin derivative in plants of the families Umbilliferae and Rutaceae, are studied. Upon direct irradiation (λ≥300㎚) of the compound in acetonitrile or benzene, a syn head-to-tail C₄-cyclodimer is obtained (Φ=0.07) while an anti C4-cyclodimer is obtained in the presence of triplet sensitizers such as benzophenone. Limettin undergoes C₄-cycloaddition reaction via the singlet exciplex when irradiated with tetramethylene with quantum yield of 0.16. The fluorescence of limettin is quenched by tetramethylene with the k_q of 4×10^9 mole^(-1) sec^(-1). Photolysis of limettin with thymine and thymidine yields a C₄-photocycloadduct through 2+2 cycloaddition between pyrone double bond of limettin and 5, 6-double bond of thymine and thymidine. The biological importance of the reaction is discussed in comparison with that of psoralens.
The New Substituent Constants in the Excited States (II)
Sang-Chul Shim,Joon-Won Park,Heui-Suk Ham,Jin-Soon Chung Korean Chemical Society 1983 Bulletin of the Korean Chemical Society Vol.4 No.1
In order to standardize the ${\sigma}^*,\;{\rho}^*$ is taken as unity for the benzoic acids by analogy with the fact that ${\rho}$ of benzoic acids in the ground state is taken as unity. The $pK_{\alpha}^*$ of many benzoic acid derivatives are determined by UV spectroscopy and fluorescence spectral analysis whenever possible. The ${\sigma}^*$ constants are derived from the Hammett equation utilizing these $pK_{\alpha}^*$ values and the $pK_{\alpha}^*$ of the benozic acid derivatives showed better correlationship with ${\sigma}^*$ than ${\sigma},\;{\sigma}^+\;and\;{\sigma}^-$ as expected. From these ${\sigma}^*$ values, ${\rho}^*$ of the phenol derivatives was calculated to be 1.28. The new standardized ${\sigma}^*$ values are calculated from the $pK_{\alpha}^*$ values of phenols since more accurate and abundant data are available for phenols than the benzoic acid derivatives.
Sang Chul Shim,Young Gil Kwon,Chil Hoon Doh,Byung Won Woo,Jin Ook Baeg,Hong Seok Kim,Tae Jeong Kim,Dong Ho Lee,Young Woo Kwak,Jin Soon Cha,Hyung Soo Lee,Jae Kook Uhm,Young Bae Park Korean Chemical Society 1990 Bulletin of the Korean Chemical Society Vol.11 No.2
Ethanolic tetra carbonylhydridoferrate solution combined with dialdehyde (no of carbon; 4,5,6) is very efficient for the selective transformation of amino group into N-heterocyclic compound. However, a large variety of both aliphatic and aromatic amines react with the ferrate-pimelaldehyde at room temperature under an atmospheric pressure of carbon monoxide to give the corresponding N-(cyclohexylmethyl)-N-alkyiamine derivatives in moderate yields instead of the corresponding N-substituted perhydroazocine derivatives.
Carbonylation of 1-Bromo-2,6-bis(bromomethyl)benzene Catalyzed by Cobalt Carbonyl
Sang Chul Shim,Shin Ae Chae,Dong Yeob Lee,Young Zoo Youn,Jae Goo Shim,Chil Hoon Doh Korean Chemical Society 1993 Bulletin of the Korean Chemical Society Vol.14 No.4
Dialkyl 1-bromobenzene-2,6-diacetates were easily prepared by the carbonylation of the moiety of benzylic bromide in 1-bromo-2,6-bis(bromomethyl)benzene with alcohol in the presence of NaOAc< ${\cdot}$3H$_2$O and a catalytic amount of Co$_2$(CO)$_8$under the atmospheric pressure of carbon monoxide at room temperature in excellent yield. Alkyl 2,6-bis(alkoxymethyl)benzoates were obtained by the carbonylation of the moiety of aryl bromide in 1-bromo-2,6-bis(alkoxymethyl)-benzene, which derived from 1-bromo-2,6-bis(bromomethyl)benzene, alcohol, NaOR, and CH$_3$I under the same conditions. Alkyl 2,6-bis(carboxymethyl)benzoate was also obtained in a trace amount for 24 hrs at room temperature.
Carbonylation of Protected or Non-protected 2-Bromobenzaldehyde Catalyzed by Cobalt Carbonyl
Sang Chul Shim,Dong Yup Lee,Heung Jin Choi,Chil Hoon Doh,Keun Tai Huh Korean Chemical Society 1994 Bulletin of the Korean Chemical Society Vol.15 No.9
The cobalt catalyzed carbonylation of bromobenzene having protected aldehyde group gives the corresponding ester in good yields, but 2-bromobenzaldehyde gives 3-alkoxyphthalide in the noticeable yield instead of alkyl 2-formylbenzoates.