2004 Fiscal Year Final Research Report Summary
Study on reactive intermediates and solvent participation by means of interplay of photochemical and thermochemical reactions
| Project/Area Number |
14340202
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Organic chemistry
|
|---|
| Research Institution | University of Hyogo (2004)
Himeji Institute of Technology (2002-2003) |
|---|
Principal Investigator |
OKUYAMA Tadashi University of Hyogo, Graduate School of Material Science, Professor, 大学院・物質理学研究科, 教授 (40029484)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
FUJITA Morifumi University of Hyogo, Graduate School of Material Science, Assistant Professor, 大学院・物質理学研究科, 助手 (00275314)
|
|---|
| Project Period (FY) |
2002 – 2004
|
| Keywords | iodonium salt / vinyl cation / cation radical / naphthalene / cycloalkyne / neighboring group participation / singlet oxygen / laser photolysis |
|---|
| Research Abstract |
Solvolysis of optically active 4-methylcyclohexylidenemethyl iodonium salt gives a rearranged cycloheptenyl product with complete retention of optical purity, indicating that primary vinyl cation is not formed. This was also the case even in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), and ionic liquids as well as in a solution of high ionic strength. However, the photosolvolysis leads to racemization of the products via formation of the primary vinylic cation. The same iodonium salt leads to racemized substitution products in the presence of a base in HFIP. The racemization takes place via elimination-addition mechanism with the cycloheptyne intermediate. Thermal reaction of styryl iodonium salt occurs via beta-phenyl participation with a benzenium ion intermediate. Photoreaction of the styryl substrate also takes place via the primary vinyl cation without participation. Observation of intermediate benzenium ion via photo-generated primary vinyl cation was attempted by laser photolysis in a nanosecond time scale, but there found no indication of formation of this bridged cation.
Photo-induced cycloaddition of naphthalene derivatives carrying a chiral side chain with o-chloranil took place stereoslectively.. Laser photolysis of this solution at 355 nm showed formation of a cation radical of the naphthalene substrate. The same cation radical was thermally generated with ferric salt in HFIP solution, and circular dichroic spectra were observed showing the Cotton effects around the wavelength of absorption. This result suggests that there is some interaction between the naphthalene ring and the chiral side chain, which is considered to be responsible for the stereoselectivity of the cycloaddition. Similar naphthalene derivatives carrying a chiral carboxylate side chain were subjected to the reaction with singlet oxygen, which led to synthesis of optically active hydroperoxides.
|
