1997 Fiscal Year Final Research Report Summary
Practical Synthesis of Phisiologically Active Substances Using Functionalized Lewis Acids
| Project/Area Number |
08555225
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (A)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 展開研究 |
|---|
| Research Field |
Synthetic chemistry
|
|---|
| Research Institution | HOKKAIDO UNIVERSITY |
|---|
Principal Investigator |
MARUOKA Keiji Hokkaido Univ., Grad.Sch.of Sci., Pro., 大学院・理学研究科, 教授 (20135304)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
OOI Takashi Hokkaido Univ., Grad.Sch.of Sci., Assist.Pro., 大学院・理学研究科, 助手 (80271708)
ASAO Naoki Hokkaido Univ., Grad.Sch.of Sci., Assoc.Pro., 大学院・理学研究科, 講師 (60241519)
|
|---|
| Project Period (FY) |
1996 – 1997
|
| Keywords | ATPH / radical reaction / conjugate alkylation / aluminum / titanium / chemoselectivity |
|---|
| Research Abstract |
A remarkable template effect in the intramolecular radical cyclization process has been observed by the successful utilization of functinalized Lewis acid, aluminum tris (2,6-diphenylphenoxide) (ATPH). For example, intramolecular radical cyclization of 3-iodopropyl 3-phenylpropynyl ether under the influence of ATPH with Bu_3SnH and catalytic amount of Et_3B in toluene at-78ﾟC for 1 h affords cyclic ether as a sole isolable product, while without ATPH under otherwise similar reaction conditions a simple reduction product is obtained as a major product with concomitant minor formation of the cyclization product. Notably, the E/Z selectivity in the cyclization products is totally opposite in the presence or absence of ATPH.The origin of this efficient template effect by ATPH would be ascribed to the well-defined reaction environment created in front of aluminum coordination center. This represents the first example of controlling radical reaction pathway with a designer Lewis acid in view
… More
of the molecular recognition approach.
Using ATPH as a functionalized Lewis acid, we have also developed a conceptually new amphiphilic conjugate alkylation for effective blocking of aldehyde carbonyls, thereby allowing the hitherto difficult conjugate addition of reactive nucleophiles to alpha, beta-unsaturated aldehydes. Among various functionalized ATPH derivatives as a designer Lewis acid possessing the specific reaction environment, aluminum tris [2,6-bis (p-fluorophenyl) phenoxide] (p-F-ATPH) and aluminum tris [2,6-bis (3,4,5-trifluorophenyl) phenoxide] (3,4,5-F_3-ATPH) were found to be highly effective for this transformation. This biomimetic system is highlighted by the first successful conjugate addition of allyllithium reagents to alpha, beta-unsaturated aldehydes by complexation with the functionalized Lewis acid, p-F-ATPH,giving the desired conjugate adducts with excellent selectivity.
In addition to these researches, chemoselective functionalization of carbonyl compounds over acetals has been achieved by bidentate organoaluminum and titanium Lewis acids based on the double electrophilic activation of carbonyls selectively. Less
|
