1998 Fiscal Year Final Research Report Summary
Epnselenonium Ion Intermediate : Isolation and Utilization in Carbon-Carbon Band Formations
| Project/Area Number |
09650957
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Synthetic chemistry
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
TOSHIMITSU Akio Institute for Chemical Research, KYOTO UNIVERSITY Associate Professor, 化学研究所, 助教授 (60127107)
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| Project Period (FY) |
1997 – 1998
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| Keywords | Episelenonium Ion / Steric Protection / Election-withdrawing Group / Carbon-Carbon Poond Formation / Chiral Carbon |
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| Research Abstract |
This report is the summary of the preliminary results obtained by the research project. Three sections constitute this report and their abstracts are as follows.
The first part describes that, in the Ritter-type reactions starting from chiral alcohols to afford amides through the anchimeric assistance of the arylseleno group, the enantiomeric excesses of the amides are better when the bulky substituents are introduced into the aryl groups. We deduced that the racemization of the chiral episelenonium ion intermediates are suppressed by the steric protection of the selenium atom from the attack of the nucleophiles. In order to support this hypothesis, we carried out the reactions of the episelenonium ion intermediates with carbon nucleophiles and found that the formation of the carbon-selenium bonds are completely suppressed by the steric protection. Thus, the steric protection was clarified to be important to stabilize the episelenonium ion intermediates.
The second part describes that, in the Rider-type reactions described above, not only the bulky substituents but also the electron-withdrawing substituents contribute to suppress the racemization of the chiral episelenonium ion intermediates. It is also clarified that these two effects work additively. It is pointed out that the racemization of the chiral episelenonium ion intermediates proceeds through the hypervalent selenium compounds.
The results of the studies on the hypervalent selenium compounds are described in the third section. It is clarified that the formation of hypervalent selenium compounds is much more facile as compared to the sulfur compounds and the hypervalent selenium compounds can be utilized in the organic syntheses.
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Research Products
(4 results)
