Synthesis of Metal–(Pentadentate-Salen) Complexes: Asymmetric Epoxidation with Aqueous Hydrogen Peroxide and Asymmetric Cyclopropanation (salenH2:N,N′-bis(salicylidene)ethylene-1,2-diamine)
作者:Hiroaki Shitama、Tsutomu Katsuki
DOI:10.1002/chem.200601420
日期:2007.6.4
manganese(III) and cobalt(II) complexes, in which the fifth ligand is expected to intramolecularly coordinate to the metal center and exert a trans effect. Indeed, high enantioselectivity has been achieved in epoxidations using aqueous hydrogen peroxide as the terminal oxidant and in cyclopropanations with these complexes as catalysts. In general, metallosalen-catalyzed reactions have been carried out
Copper Complexes of Chiral Tetradentate Binaphthyl Schiff-Base Ligands: Syntheses, X-ray Crystal Structures and Activity in Catalytic Asymmetric Cyclopropanation of Alkenes
1′-binaphthyl] and a series of chiral copper(II) complexes [CuL] were prepared in good or nearly quantitative yields. Some of the free ligands and the [CuL] complexes were structurally characterized by X-ray crystallography. Almost all the [CuL] complexes were found to be active catalysts for the asymmetric cyclopropanation of alkenes with ethyl or tert-butyl diazoacetate. Enantioselectivities of up to 77%
Chiral Bis(oxazolinyl)phenyl RuII Catalysts for Highly Enantioselective Cyclopropanation
作者:Jun-ichi Ito、Satoshi Ujiie、Hisao Nishiyama
DOI:10.1002/chem.200903514
日期:——
derivatives were achieved in the cyclopropanation of alkenes with tert‐butyl α‐diazoacetate by using 0.5 mol % of a mononuclear chiralruthenium aqua complex containing the chiralbis(oxazolinyl)phenyl ligand, which was obtained via CH activation by RuCl3⋅3 H2O in the presence of Mg and cyclooctadiene (cod). Intramolecular cyclopropanation reactions using the new Ru complex also proceed with high
In Search of High Stereocontrol for the Construction of <i>cis</i>-Disubstituted Cyclopropane Compounds. Total Synthesis of a Cyclopropane-Configured Urea-PETT Analogue That Is a HIV-1 Reverse Transcriptase Inhibitor
作者:Wenhao Hu、Daren J. Timmons、Michael P. Doyle
DOI:10.1021/ol017276b
日期:2002.3.1
[GRAPHICS]A new azetidine-figated dirhodium(II) catalyst that possesses a l-menthyl ester attachment provides significant diastereocontrol and high enantiocontrol for the formation of cis-cyclopropane products from reactions of substituted styrenes with diazo esters.
Construction of Aryliridium−Salen Complexes: Enantio- and <i>Cis</i>-Selective Cyclopropanation of Conjugated and Nonconjugated Olefins
introducing a tolyl or phenyl ligand at the apical position, respectively, via the S(E)Ar mechanism, and they were found to be efficient catalysts for cis-selective asymmetric cyclopropanation. The scope of the cyclopropanation was wide, and the reactions of not only conjugated mono-, di-, and trisubstituted olefins but also nonconjugated terminal olefins proceeded with high enantio- and cis-selectivity