• Bulletin of the Korean Chemical Society
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• v.30 no.10
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• pp.2283-2286
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• 2009

A convenient route for the preparation of water soluble polythiophenes is described. Reactions involving highly active zinc metal show unique properties, viz. tolerance of the ester group and regioselectivity to the thiophene ring. Poly [3-(ethyl-n-alkanoate)thiophene-2,5-diyl]s, poly [3-(n-carboxyalkyl)thiophene-2,5-diyl]s, and poly [3-(potassium- n-alkanoate)thiophene-2,5-diyl]s were easily prepared by utilizing highly active zinc.

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3817-3822
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• 2012

Various alkenylphosphonates were prepared via the palladium-catalyzed oxidative arylation of cinnamylphosphonates with arenes. The regioselectivity during the ${\beta}$-H elimination of the corresponding alkylpalladium intermediate was governed most likely by steric factors.

• Bulletin of the Korean Chemical Society
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• v.13 no.1
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• pp.41-45
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• 1992

Thermal cycloaddition of t-butyl trimethylsilyl thioketone (1) with 2-substituted dienes such as isoprene and 2-trimethylsilyloxy-1,3-butadiene occurred smoothly at 80${\circ}C$ to afford regioiomeric mixtures of cycloadducts. On the other hand, similar treatment of 1 with 1-substituted dienes such as trans-1,3-pentadiene, 1-methoxy-and 1-acetoxy-1,3-butadiene and Danishefsky's diene afforded a single regioisomeric adduct, respectively. Protodesilylation of the silylated adducts 8 and 11 could also be performed with ease.

• Bulletin of the Korean Chemical Society
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• v.17 no.10
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• pp.892-899
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• 1996

In order to elucidate the effect of alkoxy substituent in thexylborane and hence establish their usefulness as hydroborating agent, reactions of alkenes and alkynes with thexylalkoxyborane (ThxBHOR; R=Et, i-Pr, i-Bu, sec-Bu, t-Bu, Ph) were investigated in detail. The reagents readily hydroborated alkenes and alkynes of various structural types at 25 ℃ in excellent regioselectivity. The selectivity increases consistently with increasing steric size of alkoxy substituent. Especially, the selectivity achieved by the sec-butoxy derivative is comparable to that previously achieved by thexylhaloborane-methyl sulfide (ThxBHX·SMe2), the most selective hydroborating agent known.

• Bulletin of the Korean Chemical Society
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• v.20 no.4
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• pp.441-444
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• 1999

The alkyl Grignard addition reaction on 1-benzyltetrazolylimine proceeds to give N-alkylated products (azophilic addition) and, in contrast, the same reaction on 2-benzyltetrazolylimine produced predominantly C-alkylated products (carbophilic addition). In this report we described theoretical explanations for this experimental finding on the basis of the frontier molecular orbitals and the electrostatic nature of the reactants and the reaction intermediates.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.153-154
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• 2006

The development of metal catalysts that can polymerize or copolymerize "polar" $Ch_2=CHX$ monomers by insertion mechanisms would significantly expand the scope of metal-catalyzed polymerization and enable the synthesis of new materials with enhanced properties. We have studied the reactions of single-site olefin polymerization catalysts with vinyl chloride, acrylonitrile, and vinyl ethers, in order to probe monomer coordination trends, insertion rates and regioselectivity, and the structures and reactivity of metal alkyls that contain functional groups on the alpha and beta positions of the alkyl chain. These studies provide insights to the key issues that underlie the "polar monomer" problem. Copolymerization of olefins and selected vinyl ethers has been achieved.

• Archives of Pharmacal Research
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• v.13 no.1
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• pp.5-8
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• 1990

The cycloaddition of the newely synthesized 5-(2-thienyl)methylene derivatives of thiazolidinone-4-thiones, 2a-c to acrylonitrile (3a), ethylacrylate (3b), N-phenylmaleimide (6) and dimethyl fumarate (8) has been evaluated. Under thermal reaction conditions [4 +2] cycloaddition proceeds with complete site and regioselectivity to yield the cycloadduct, 4, 5, 7 and 9, respectively. The antimicrobial activities of some of the new products were tested.

• Journal of the Korean Chemical Society
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• v.33 no.2
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• pp.247-256
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• 1989

4-Acetyl-5,6-dihydro-2-methyl-1,4-thiazine carboxylic acid derivatives 24 were prepared by ring expansion of corresponding thiazolidine sulfoxides. Oxidation of 2-methyl-1,3-thiazolidine-2-acetic acid derivatives 12 gave a mixture of cis and trans sulfoxides, 14 and 15. Assignments of the cis and trans sulfoxides were based on the $^1HNMR$ and IR spectroscopy and regioselectivity of deuterium exchange reaction. With PTSA as acid catalyst both the cis and trans sulfoxide, 14 and 15 were transformed via sulfenic acid 18 to dihydro-1,4-thiazine 24. However, under the neutral conditions (in DMF at $100^{\circ}C$) the trans sulfoxides 15 rearranged via sulfenic acid 21 to isomeric dihydrothiazines 27. The mechanism of formations of 24 and 27 is also discussed.

• Bulletin of the Korean Chemical Society
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• v.26 no.9
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• pp.1339-1343
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• 2005

The N-inversion energies and nucleophilic ring-opening reactions of N-substituted aziridine compounds are investigated using B3LYP/6-31+$G^*$ methods, where substituents (R) on the nitrogen atom has been H (1), Me (2), Ph (3), Bn (4), CHMePh (5), $CO_2Me$ (6), COPh (7) and $SO_2Ph$ (8). The N-inversion energy with X group are decreased as the following order: R = CHMePh (17.06 kcal/mol) $\gt$ Me (16.97) $\gt$ Bn (16.70) $\gt$ H (16.64) $\gt$ $SO_2Ph$ (12.18) $\gt$ Ph (8.91) $\gt$ COPh (5.75) $\gt$ $CO_2Me$ (5.48). For reactivity of the ring opening toward cyanide ion, the aziridine 6 (R=$CO_2Me$) is shown to be the most reactive one. During the ring opening of aziridine 6 by CN$^{\ominus}$, the torsional OCNC angle becomes near to $180^{\circ}$, where the geometry allows for the effective incorporation of electrons of the nitrogen atom to the C=O bond. It would be a possible driving force for nucleophilic ring opening reaction as well as decreasing the N-inversion energy barrier. Regarding to the regioselectivity, the orientation of nucleophile in ring opening reaction appears to be different in the case of 9 and 10. The results are discussed in terms of steric/electronic effect of the $C_2$-substituents.

• Journal of the Korean Chemical Society
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• v.26 no.1
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• pp.7-17
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• 1982

In order to predict substituent and Lewis acid effects on the regiospecificity of the Diels-Alder reaction, and to investigate the competition for the complexation of Lewis acid between diene and dienophile, frontier orbital theory has been applied to thermal and catalyzed Diels-Alder reaction by means of CNDO/2 MO method. It has been found that: (1) Lewis acid coordinated preferentially with diene rather than dienophile when carbonyl oxygen of acetoxy substituted diene had larger negative atomic charges than that of dienophile. (2) Most of the reaction were neutral electron demand type, and hence 4-C, 2-C and quantitative secondary orbital interacion methods were generally in good accord with experiments. (3) Sulfur activated the adjacent terminal carbon atom greatly to increase diene LUMO-dienophile HOMO interaction through vacant-d-orbital participation, and played an important role in controlling regioselectivity of neutral electron demand reaction type.