• Bulletin of the Korean Chemical Society
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• v.19 no.6
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• pp.634-641
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• 1998

Quasiclassical trajectory calculations were carried out for the reactions of $H+H_2$ (V=O, J=O) and its isotope variants on the Siegbahn-Liu-Truhlar-Horowitz potential energy surface for the relative energies E between 6 and 150 kcal/mol. The goal of the work was to understand the inter- and intramolecular isotope effects. We examine the relative motion of reactants during the collision using the method of analysis that monitors the intermolecular properties (internuclear distances, geometry of reactants, and final product). As in other works, we find that the heavier the incoming atom is, the greater the reaction cross section is at the same collision energy. Using the method of analysis we prove that the intermolecular isotope effect is contributed mainly by differences in reorientation due to the different reduced masses. We show that above E=30 kcal/mol recrossing also contributes to the intermolecular isotope effect. For the intramolecular isotope effect in the reactions of H+HD and T+HD, we reach the same conclusions as in the systems of $O(^3P)+HD$, F+HD, and Cl+HD. That is, the intramolecular isotope effect below E=150 kcal/mol is contributed by reorientation, recrossing, and knockout type reactions.

• Bulletin of the Korean Chemical Society
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• v.20 no.4
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• pp.422-426
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• 1999

The Grignard reactions of bis(chloromethyl)dimethylsilane (1) with trimethylchlorosilane (2) in THF give both the intermolecular C-Si coupling and intramolecular C-C coupling products. At beginning stage, 1 reacts with Mg to give the mono-Grignard reagent ClCH2Me2SiCH2MgCl (1) which undergoes the C-Si coupling reaction to give MC2Si(CH2SiMe3)2 3, or C-C coupling to a mixture of formula Me3SiCH2(SiMe2CH2CH2)nR1 (n = 1, 2, 3, ..; 4a, R1I = H: 4b, R1 = SiMe3). In the reaction, two reaction pathways are involved: a) Ⅰ reacts with 2 to give Me3SiCH2SiMe2CH2Cl 6 which further reacts with Mg to afford a Me2SiCH2Mel-SiCH2MgCl (Ⅱ) or b) I cyclizes intramolecularly to a silacyclopropane intermediate A, which undergoes a ring-opening polymerization by the nucleophilic attack of the intermediates I or Ⅱ, followed by the termination reaction with H2O and 2, to give 4a and 4b, respectively. As the mole ratio of 2/1 increased from 2 to 16 folds, the formation of product 3 increased from 16% to 47% while the formation of polymeric products 4 was reduced from 60% to 40%. The intermolecular C-Si coupling reaction of the pathway a becomes more favorable than the intramolecular C-C coupling reaction of the pathways b at the higher mole ratio of 2/1.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1743-1748
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• 2014

A facile and effective method has been developed for the synthesis of a novel series of benzofuran derivatives via N-acylation, O-alkylation and intramolecular condensation reactions, starting from readily available substituted o-hydroxy aryl ketone, and chloroacetyl arylamides. This metal-free transition process is characterized by mild reaction conditions, atom economy, short reaction time and a high yield with a decreased amount of by-products.

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1841-1842
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• 2010

• Bulletin of the Korean Chemical Society
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• v.19 no.8
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• pp.818-819
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• 1998

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2343-2353
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• 2007

We report the application of time-dependent density functional theory (TDDFT) to the calculation of potential energy profile relevant to the excited state intramolecular proton transfer (ESIPT) processes in title molecules. The TDDFT single point energy calculations along the reaction path have been performed using the CIS optimized structure in the excited state. In addition to the Stokes shifts, the transition energies including absorption, fluorescence, and 0-0 transition are estimated from the TDDFT potential energy profiles along the proton transfer coordinate. The excited state TDDFT potential energy profile of SA and 3ASA resulted in very flat function of the OH distance in the range ROH = 1.0-1.6 A, in contrast to the relatively deep single minimum function in the ground state. Furthermore, we obtained very shallow double minima in the excited state potential energy profile of SA and 3ASA in contrast to the single minimum observed in the previous work. The change of potential energy profile along the reaction path induced by the substitution of electron donating groups (-NH2 and -OCH3) at different sites has been investigated. Substitution at para position with respect to the phenolic OH group showed strong suppression of excited state proton dislocation compared with unsubstitued SA, while substitution at ortho position hardly affected the shape of the ESIPT curve. The TDDFT results are discussed in comparison with those of CASPT2 method.

• Journal of Photoscience
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• v.10 no.1
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• pp.21-35
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• 2003

The photoinitiated intramolecular ylide-olefin addition has been developed as an approach for the construction of one ring and two chiral centers, two rings and three chiral centers or three rings and six chiral centers in a single experimental operation from relatively simple starting materials. These investigations have uncovered several interesting and unusual reactions, which are sensitive to controls such as wavelength, temperature and solvent.

• YAKHAK HOEJI
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• v.39 no.1
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• pp.41-47
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• 1995

An efficient and stereoselective synthetic route to the trisubstituted hydroxy cyclopentane as an useful synthetic intermediate for carbaprostacyclin is described. Pd(0)-mediated intramolecular alkylation of allylic carbonate has been employed as a key reaction.

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.362.2-362.2
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• 2002

Antofine belongs to the Phenathroindolizidine group of alkaloids. This natural products exhibit interesting biological properties such as antitumour activity. and anti-inflammentory. Wittig reaction of phenathrenealdehyde with the phosponium salt provided the phenathreneazidealkene in good yield. Intramolecular 1.3-dipolar cycloaddition of the resulting azidealkent in refluxing benzene proceeded the imine. It was reduced with cyanoborohydride of Noyori's Asymmetric Hydrogenation. (omitted)

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2719-2723
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• 2012

A kinetic study is reported for nucleophilic substitution reactions of benzyl 4-pyridyl carbonate 6 with a series of alicyclic secondary amines in MeCN. The plot of pseudo-first-order rate constant ($k_{obsd}$) vs. [amine] curves upward, which is typical for reactions reported previously to proceed through a stepwise mechanism with two intermediates (i.e., a zwitterionic tetrahedral intermediate $T^{\pm}$ and its deprotonated form $T^-$). Dissection of $k_{obsd}$ into the second- and third-order rate constants (i.e., $Kk_2$ and $Kk_3$, respectively) reveals that $Kk_3$ is significantly larger than $Kk_2$, indicating that the reactions proceed mainly through the deprotonation pathway (i.e., the $k_3$ process) in a high [amine] region. This contrasts to the recent report that the corresponding aminolysis of benzyl 2-pyridyl carbonate 5 proceeds through a forced concerted mechanism. An intramolecular H-bonding interaction was suggested to force the reactions of 5 to proceed through a concerted mechanism, since it could accelerate the rate of leaving-group expulsion (i.e., an increase in $k_2$). However, such H-bonding interaction, which could increase $k_2$, is structurally impossible for the reactions of 6. Thus, presence or absence of an intramolecular H-bonding interaction has been suggested to be responsible for the contrasting reaction mechanisms (i.e., a forced concerted mechanism for the reaction of 5 vs. a stepwise mechanism with $T^{\pm}$ and $T^-$ as intermediates for that of 6).