2006 Fiscal Year Final Research Report Summary
Stereocontrol of high speed reaction by chiral tether
| Project/Area Number |
16350026
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Organic chemistry
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| Research Institution | University of Hyogo |
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Principal Investigator |
SUGIMURA Takashi University of Hyogo, Graduate School of material Science, Professor, 大学院物質理学研究科, 教授 (30187661)
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| Project Period (FY) |
2004 – 2006
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| Keywords | Stereoselectivity / Synthetic chemistry / Molecular recoanition / Carbenoid / High speed reaction / Addition reaction / Rhodium catalyst / Entropy |
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| Research Abstract |
Intramolecular reaction using 2,4-pentanediol tether is known to result in high stereoselectivity for varied reactions. In this project, high speed reactions were mainly studied to establish novel synthetic method and to disclose the stereocontrol mechanism of intramolecular reaction. Diazo group in the presence of rhodium catalysts strongly recognized the regioslectivity of the aromatic group connected through the tether, and order of intrinsic reactivity of functional groups could be inverted by the force of regiocontrol By this force, cycloheptatrienols were obtained by the reaction of phenol analogues. Some C-H insertion reaction, that can be less reactive than the addition to a proximal aromatic ring, could also achieved by the same force. The functional group is dependent of the reaction rate, but the stereoselectivity was not. Remote addition under strict stereocontrol was also demonstrated,
Radical reaction using 2,4-pentanediol tether has been known to show very poor stereoselectivity. The reason was found to be due to slower conformational change than the intramolecular addition. By stabilizing the initially generated radical, the addition became slower than the conformational change, and as a result, 10% diastereomeric excess was improved to over 99% de. This can be the first clear example of the switching of stereocontrolled and uncontrolled reactions by closing the Curtain-Hammett borderline.
In the chiral tethered ketene-olefin addition, strong structure dependency on the product selectivity was found. The reaction was cyclic olefin or a-substituted olefin gives over 95% de, while a-unsubstituted olefin gave ca 10% de. This low stereoselectivity as well as the other high stereoselectivity does not depend on the reaction temperature from-50 to 270℃. This finding indicates a new process in the ketene-olefin addition, but the reason to cause difference necessitated further mechanistic study.
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Research Products
(36 results)
