| Co-Investigator(Kenkyū-buntansha) |
OKU Akira Kyoto Institute of Technology, Chemistry, Professor, 工芸学部, 教授 (50027885)
MIURA Katsukiyo University of Tsukuba, Chemistry, Lecturer, 化学系, 講師 (20251035)
HOJO Makoto University of Tsukuba, Chemistry, Lecturer, 化学系, 助教授 (50229150)
NAOTA Ken Osaka University, Chemistry, Professor, 大学院・基礎工学研究科, 助教授 (20164113)
IWASAWA Shinji Tokyo Institute of Technology, Chemistry, Professor, 大学院・理工学研究科, 教授 (40168563)
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| Research Abstract |
1. Silicon-directed Cyclization of Vinylysilanes : Stereoselective Synthesis of Tetrahydrofurans and Tetrahydropyrans
Silicon-directed stereoselective syn addition of hydroxy group to olefinic double bond occurs intramolecularly in an acid-catalyzed cyclization of vinylsilanes bearing hydroxy group. The cyclization proceeds by stereospecific syn addition of the hydroxy group. Vinylsilanes, (Z)-5-silyl-4-penten-1-ols bearing a substituent on the methylene tether, smoothly undergo the acid-catalyzed cyclization to give trans-2,5-, cis-2,4-, and trans-2,3-disubstituted tetrahydrofurans, respectively, with moderate to high stereoselectivity.
2. Acid-Catalyzed Cyclization of Vinylsilanes Bearing an Amino Group. Stereoselective Synthesis of Pyrrolidines
In the presence of an acid catalyst, vinylsilanes bearing an amino group protected by an electron-withdrawing group were smoothly cyclized to 2-(silylmethyl)pyrrolidines. This cyclization was utilized for the stereoselective synthesis of 2,n-dis
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ubstituted pyrrolidines (n=3-5).
3. Unprecedented Manganese-Mediated Reactions : Generation of Non-Stabilized Carbonyl Ylids
Activated manganese generates nonstabilized carbonyl ylides from bis(chloromethyl) ethers as a precursor, and using this system with manganese as a reductant, the reactions of the ylides with electron-deficient dipolarophiles can be attained without the direct reduction of dipolarophiles by the reductant.
4. Manganese Ate Species : Generation and Reactions with Electrophiles
Trialkylmanganese(II) ate reagents, "R_3MnLi" reacted with iodomethylsulfides to produce thiomethylmanganese reagents, where the manganate serves as a reductant not an alkylation agent. The reductive behavior of trialkylmanganese(II) ate reagents provides a protocol for the direct generation of a new class of reagents, thiomethylmanganese reagents with structural variety, and the generated thiomethylmanganese reagents reacted with allyl bromides, enones and aldehydes.
5. Radical Cyclization of 1,6-Enynes Using Allylstannanes and New Radical Reactions Using Stannyl Enolates as Radical Transfer Agents
6. New Method for Introduction of a Silyl Group into α,β-Enones Using a Disilane Catalyzed by a Copper(I) salt.
The reaction of a disilane with a Cu(I) salt efficiently induces cleavage of the Si-Si bond to generate a silyl nucleophile in an aprotic polar solvent and its 1,4-addition to α,β-unsaturated enones smoothly proceeds with a catalytic amount of a Cu(I) salt were found. This reaction is successfully applied to hexamethyldisilane to generate a trimethylsilyl nucleophile, hitherto not easily accessible.
7. The first systematic studies on the structure and reactivities of C-and N-bound isomers of transition metal a-cyanocarbanions have been carried out. Strong contribution of stereochemistry of ligands to their reactivities and catalysis has been clarified in view of structural analysis, organometallic transformations, and mechanistic investigations
8. Dynamic control of the reaction pathways in the pentacarbonyltungsten catalyzed cyclization of ω-acetylenic silyl enol ethers is achieved giving either exo or endo cyclized product selectively by the appropriate choice of the reaction conditions. Less
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