Asymmetric Synthesis of Di- and Trisubstituted Cyclopropanes through an Intramolecular Ring Closure
作者:Jeffrey Kallemeyn、Mathew Mulhern、Yi-Yin Ku
DOI:10.1055/s-0030-1259535
日期:2011.3
An asymmetric synthesis of di- and trisubstituted cyclopropanes proceeding through an intramolecular ringclosure of activated chiral benzyl alcohols has been developed. The chiral alcohol intermediates are obtained from asymmetric reduction of readily available 1,4-keto esters and undergo a one-pot activation and ringclosure to provide the ester-functionalized cyclopropanes in high enantio- and diastereomeric
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%
Highly Enantioselective Cyclopropanation of Styrenes and Diazoacetates Catalyzed by 3-Oxobutylideneaminatocobalt(II) Complexes, Part 1. Designs of Cobalt Complex Catalysts and the Effects of Donating Ligands
Highlyenantioselective cyclopropanation of styrene derivatives and diazoacetates was effectively catalyzed by reasonably designed 3-oxobutylideneaminatocobalt(II) complexes, whose ligands were prepared from 1,2-dimesitylethylenediamine and alkyl 3-oxobutanoates. The steric demand of the diamine unit of the complexes seriously influenced the enantioselectivity, and the ester groups on their side chains
合理设计的 3-氧代亚丁基氨基钴 (II) 配合物可有效催化苯乙烯衍生物和重氮乙酸酯的高对映选择性环丙烷化,其配体由 1,2-二甲基亚乙基二胺和 3-氧代丁酸烷基酯制备。配合物二胺单元的空间需求严重影响了对映选择性,其侧链上的酯基在一定程度上提高了反式选择性。添加催化量的 N-甲基咪唑显着加速了反应并提高了对映选择性,因为它作为轴向配体与配合物的中心钴原子配位。醇或含水醇溶剂对于 1-取代的 1-苯基乙烯的环丙烷化也特别有效,以在含水甲醇中实现高对映选择性。
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
Synthesis of a New Chiral Nonracemic <i>C</i><sub>2</sub>-Symmetric 2,2‘-Bipyridyl Ligand and Its Application in Copper(I)-Catalyzed Enantioselective Cyclopropanation Reactions
作者:Michael P. A. Lyle、Peter D. Wilson
DOI:10.1021/ol049853c
日期:2004.3.1
synthesis of a low molecular weight, chiral nonracemic and C(2)-symmetric bipyridyl ligand is reported. The ligand was prepared using a catalytic asymmetric dihydroxylation reaction of a pyrindine as a key step. The ligand was evaluated in the asymmetric copper(I)-catalyzed cyclopropanation reactions of a series of alkenes and diazoesters. Very high diastereoselectivities and enantioselectivities were