2007 Fiscal Year Final Research Report Summary
Reaction and Characterization of Hypervalent Organo-λ^<3->bromanes
| Project/Area Number |
18390005
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Chemical pharmacy
|
|---|
| Research Institution | The University of Tokushima |
|---|
Principal Investigator |
OCHIAI Masahito The University of Tokushima, Institute of Health Biosciences, Graduate School, Professor (50127065)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
MIYAMOTO Kazunori The University of Tokushima, Institute of Health Biosciences, Graduate School, Assistant Professor (40403696)
|
|---|
| Project Period (FY) |
2006 – 2007
|
| Keywords | Hypervalent / Bromine / Iodine / Leaving group / Solvolysis / Nucleophilic substitution / Cation / Carbene |
|---|
| Research Abstract |
(I) Reaction of difluoro-λ^3-bromane with alkynylstannanes (2.2 equiv) in the presence of BF_3 Et_2O in dichloromethane results in oxidative homocoupling to give symmetrical 1,3-diynes. The reaction involves a Michael addition of alkynylstannanes to the initial formed alkynyl-λ^3-bromanes. Cross-coupling of alkynyl-λ^3-bromanes with alkynylstannanes affords unsymmetrical 1,3-diynes.
(II) Cyclohexenyl- and cyclopentenyl-λ^3-bromanes were prepared from vinyl borates by the reaction with difluoro-k^3-bromane via borane-bromane (III) exchange. Solvolysis of cyclopentenyl-λ^3-bromane in aqueous alcohols afforded a good yield of cyclopentanone via generation of cyclopentenyl cation. We have measured the rates of solvolysis, which show very high leaving group ability of aryl-λ^3-bromanyl groups.
Intermolecular transylidation between halonium ylides under thermal and catalytic (rhodium (II) acetate) conditions, which makes it possible to synthesize a hitherto unknown kind of aliphatic chloronium ylides as well as a variety of bromonium and iodonium ylides, was developed. Compared to the iodonium ylide, the chloronium and bromonium ylides serve as a better progenitor for generation of carbenes (or carbenoids) and efficiently undergo cyclopropanation of olefins such as cyclooctadiene under uncatalyzed thermal conditions. A greater leaving group ability of the λ^3-chroranyl and λ^3-bromanyl groups compared to that of the λ^3-iodanyl group seems to be responsible for the observed differences in reactivity between these halonium ylides.
|
Research Products
(86 results)
