2003 Fiscal Year Final Research Report Summary
Elucidation of Biradical Character in pi-Conjugated Hydrocarbons Caused by Annelation with Strained Bicycloalkene Frameworks
| Project/Area Number |
14340196
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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 | KYOTO UNIVUERSITY |
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Principal Investigator |
KOMATSHU Koichi Kyoto University, Institute for Chemical Research, Professor, 化学研究所, 教授 (70026243)
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| Co-Investigator(Kenkyū-buntansha) |
NISHINAGA Tohru Kyoto University, Institute for Chemical Research, Assistant Professor, 化学研究所, 助手 (30281108)
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| Project Period (FY) |
2002 – 2003
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| Keywords | aromaticity / antiaromaticity / sigma-pi interaction / bicyclic hydrocarbon / cyclooctatetraene / radical cation / X-ray crystallography / oligothiophene |
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| Research Abstract |
(1)The most essential aromatic hydrocarbon, benzene (1), and cyclic polyene, cyclooctatetraene (COT, 2), annelated with a highly strained bicyclic system, bicyclo[2.1.1]hexene (BCH), were synthesized. Their aromaticity and antiaromaticity were examined by the use of theoretical calculations and spectral and electrochemical measurements.
(2) One-electron oxidation of benzene 1 with SbCl_5 was found to cause rearrangement of 1 to a novel naphthalene derivative 3 annelated with the BCH units at 1,2- and 3,4-positions. The X-ray structural analysis of 3 demonstrated that the BCH-annelated 6-membered ring is more aromatic than the other ring owing to bond-length equalization. It can be oxidized to a stable radical cation because of the considerably raised HOMO energy levels.
(3) Benzene 1 exhibited the reactivity typical for the polyene rather than an aromatic compound. Thus, it was oxidized by m-CPBA and underwent Symmons-Smith reactions to give the corresponding all-cis tri-epoxide and tri-cyclopropane derivatives in high yields.
(4) Because of the annelation with strained BCH systems, naphthalene 3 readily underwent oxidation with air under irradiation of room light to give a novel macrocyclic alkyne having a two carbonyl groups and two cis-cyclobutane-1,4-diyl units. This was shown to be formed by retro[2+2+2] cleavage reaction of the endoperoxide first formed at the 1,4-positions of the BCH-annelated naphthalene. This is due to the high biradical character of naphthalene 3.
(5) A series of oligothiophenes (2-,3-,4-,6-, and 8-mers) completely surrounded by bicyclo[2.2.2]octene units were synthesized, and were converted to stable radical cation salts or dication salts, whose precise structures were determined by X-ray crystallography. These are considered as pertinent models for polaron or bipolaron of the p-doped states of oligothiophenes.
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Research Products
(18 results)
