1998 Fiscal Year Final Research Report Summary
Studies of Stereoceiective Preparation of 7-Membered Heterocycles Utilyzing Intramolecular
| Project/Area Number |
09650940
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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 |
有機工業化学
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| Research Institution | Yamaguchi University |
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Principal Investigator |
NOGUCHI Michihiko Yamaguchi University, Faculty of Engineering, Professor, 工学部, 教授 (10108772)
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| Co-Investigator(Kenkyū-buntansha) |
AKIKO Nishida Yamaguchi University, Faculty of Engineering, Research Associate, 工学部, 助手 (70144920)
HIDETOSHI Yamamoto Yamaguchi University, Faculty of Engineering, Assistant Professor, 工学部, 講師 (70264116)
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| Project Period (FY) |
1997 – 1998
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| Keywords | azepine-ring formation / intramolecular type III ene reaction / carbonyl ene reaction / imine ene reaction / olefin ene reaction / 1,6-hydrogen shift / conjugated azomethine ylide / 1,7-electrocyclization |
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| Research Abstract |
The thermal reaction of the α,β-unsaturated aldehydes bearing an (alk-2-enyl) amino moiety at the β-position gave the azepine derivatives in good to excellent yields. When these groups were a part of heterocycles, the azepine derivatives fused by the heterocyclic systems were formed. The imines of the aldehydes also afforded the azepine derivatives. The vinyl substrates, obtained by the condensation reaction of the aldehydes with activated methylene compounds, gave the azepine derivatives and/or hetero Diels-Alder adducts depending on the kind of the substituents both on the vinyl and alkenyl parts. The similar reactions of β-(alk-2-enyl) aminoacroleins gave the simple azepine derivatives. The reactivity for the azepine-ring formation of the acroleins depended on the substituent (R) on the α-position; the acrolein bearing methoxycarbonyl group at the α-position is still obscure, we suggest that the steric bulkyness of the α-substituents should affect on the cyclization step.
These azepine-ring formation could be regarded as the intramolecular carbonyl, imine, and olefin ene reactions classified as a Type III ene reaction. Therein, the reactions proceeded in a highly stereoselective manner; when the substrates having alkenylamino moieties with the E-configuration were allowed to react, the azepine derivatives with the 4,5-cis configuration were obtained. The PM3 molecular orbital calculations of the model reactions suggest that the azepine-ring formation is constituted of two consecutive orbital-allowed reactions; 1,6-shift of the allylic hydrogen of the alkenylamino moiety to the carbonyl oxygen (or immune nitrogen) leading to conjugated azomethine ylides and 1,7-electrocyclization of the azomethine ylides.
In order to obtain further informations on the reaction mechanism, both imine and carbonyl ene reactions using the aldehydes bearing a chiral center at the alkenylamino moiety have performed a self-immolating chirality transfer to the azepine ring.
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