Synthesis of amino acid derived imidazolidinium salts as new NHC precatalysts
摘要:
The preparation of new chiral symmetrically and unsymmetrically N,N'-disubstituted imidazolium based NHC salts Ib, IIb, IIIa-c and IVc-h from the amino acids L-proline and L-phenylalanine, is reported. Some preliminary tests have been carried out, demonstrating that the chiral NHCs give chiral induction in organometallic catalysis and can be used as organocatalysts. (C) 2011 Elsevier Ltd. All rights reserved.
Chiral alkoxy-imidazolinium salts are easily available via a five-step procedure starting from β-aminoalcohols. This new family of alkoxy-N-heterocyclic carbene (NHC) precursors is shown to be highly active in the enantioselective copper-catalysed conjugateaddition to cyclic enones. Complete conversion with lowcatalystloading and good enantiomeric excesses up to 93% were obtained at room temperature
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‐Selective Copper(I)‐Catalyzed Alkyne Semihydrogenation with Tethered Cu–Alkoxide Complexes
作者:Felix Pape、Niklas O. Thiel、Johannes F. Teichert
DOI:10.1002/chem.201501739
日期:2015.11.2
A highly stereoselective alkynesemihydrogenation with copper(I) complexes is reported. Copper–N‐heterocyclic carbene complex catalysts, bearing an intramolecular CuO bond, allow for the direct transfer of both hydrogen atoms from dihydrogen to the alkyne. The corresponding alkenes can be isolated with high Z selectivity and negligible overreduction to the alkane.
Stable enols from Grignard addition to 1,2-diesters: serendipity rules
作者:Olivier J.-C Nicaise、Douglas M Mans、Andrew D Morrow、Emilio Villa Hefti、Elizabeth M Palkovacs、Rajesh K Singh、Malgorzata A Zukowska、Matthew D Morin
DOI:10.1016/s0040-4020(03)01065-2
日期:2003.8
remarkably stableenol from the reaction of EtMgBr with a 1,2-diester was accidentally discovered. This compound was spectroscopically characterized (1H and 13C NMR, IR), and both methyl carbonate and trimethylsilyl ether derivatives were prepared. A mechanism for the selective formation of the stableenol ester and its corresponding keto form was suggested, and the kinetic stability of the enol was also
偶然发现了EtMgBr与1,2-二酯反应生成的温度稳定的烯醇。对该化合物进行了光谱表征(1 H和13制备1 H NMR和IR,以及碳酸甲酯和三甲基甲硅烷基醚衍生物。提出了选择性形成稳定的烯醇酯及其相应的酮形式的机理,并且还记录了烯醇的动力学稳定性。使用其他格氏试剂以及其他1,2-二酯证明了对这种稳定的烯醇酯的观察的普遍性。EtMgBr与一系列1,2-酰胺酯的反应也产生稳定的烯醇酰胺。烯醇酯的显着稳定性归因于这些化合物的芳基酯部分中存在的空间位阻,进一步的研究将探讨这种作用的起源。
Copper-catalyzed asymmetric addition of arylboronates to isatins: a catalytic cycle involving alkoxocopper intermediates
作者:Ryo Shintani、Keishi Takatsu、Tamio Hayashi
DOI:10.1039/c0cc01635g
日期:——
A copper-catalyzedaddition of arylboronates to isatins has been developed to give 3-aryl-3-hydroxy-2-oxindoles under mild conditions. The catalytic cycle of this process has been examined through a series of stoichiometric reactions and an effective asymmetric variant has also been described by the use of a chiral N-heterocyclic carbene ligand.
Ruthenium Metallacycles Derived from 14-Electron Complexes. New Insights into Olefin Metathesis Intermediates
作者:Anna G. Wenzel、Robert H. Grubbs
DOI:10.1021/ja0666598
日期:2006.12.1
Ruthenium(IV) metallacycles derived from both ethylene and propene are reported. The propene-derived metallacycles represent the first observed examples of substituted ruthenacyclobutanes and offer new insight into the preferred stereochemical orientation about metathesis intermediates. In addition, a metallacycle possessing an unsymmetrical N-heterocyclic carbene (NHC) ligand was prepared and investigated