作者:Wei Wei、Xi-Jie Dai、Haining Wang、Chenchen Li、Xiaobo Yang、Chao-Jun Li
DOI:10.1039/c7sc04207h
日期:——
Natural availability of carbonyl groups offers reductive carbonyl coupling tremendous synthetic potential for efficient olefin synthesis, yet the catalytic carbonyl cross-coupling remains largely elusive. We report herein such a reaction, mediated by hydrazine under ruthenium(II) catalysis. This method enables facile and selective cross-couplings of two unsymmetrical carbonyl compounds in either an
羰基的自然可用性为有效的烯烃合成提供了还原性羰基偶联的巨大合成潜力,但催化羰基的交叉偶联仍然很难实现。我们在本文中报道了在钌(II)催化下由肼介导的这种反应。该方法能够以分子间或分子内的方式使两种不对称羰基化合物容易且选择性地交叉偶联。此外,该化学物质可容纳多种底物,在温和的反应条件下以良好的官能团耐受性进行,并产生化学计量的良性副产物。重要的是,KO t Bu和双齿膦dmpe的共存对于这种转化至关重要。
Regioselective and Stereospecific Dehydrogenative Annulation Utilizing Silylium Ion-Activated Alkenes
annulation products retained the stereochemistry in cases of the reactions using internal alkenes. The use of diisopropyl(1-naphthyl)silane (2) instead of 1 also resulted in annulation to obtain the 2,3-dihydro-1-sila-1H-phenalene derivatives 6. Electrophilic aromatic substitution at the 8-position was predominant, despite the two potentially reactive positions on the naphthyl group. The steric hindrance
Pair-Selective Coupling of Alkynes with Alkenes on Zirconocene Complex
作者:Tamotsu Takahashi、Zhenfeng Xi、Christophe J. Rousset、Noriyuki Suzuki
DOI:10.1246/cl.1993.1001
日期:1993.6
When ethylene and alkynes such as 4-octyne and diphenylacetylene were treated with Cp2ZrBu2 highly pair selective coupling products were formed in high yields. Similarly, styrene or trimethylvinylsilane also afforded cross coupling products with alkynes on zirconocene complex.
The reaction of various cyclic and acyclic alkynes with lithium dust (2% sodium) to form vicinal dilithioalkenes has been investigated: Aliphatic alkynes, e.g. 3-hexyne (27a), exclusively afford the corresponding (E)-dilithioalkenes, insoluble solids which are stable at room temperature and allow access to a variety of tetrasubstituted olefins in acceptable yields
Epoxidation of olefins by β-bromoalkoxydimethylsulfonium ylides
作者:George Majetich、Joel Shimkus、Yang Li
DOI:10.1016/j.tetlet.2010.10.068
日期:2010.12
Olefins can be converted to their respective epoxides in a one-pot procedure by dissolving the olefin in anhydrous DMSO, adding NBS to the reaction mixture to generate a beta-bromoalkoxydimethylsulfonium ylide, and then adding DBU to the reaction mixture. A large variety of alkenes were successfully epoxidized with yields largely dependent on the structure of the alkene. Most importantly, the facial selectivity of this one-pot process is the opposite of that observed when using traditional epoxidizing reagents. Electron-poor alkenes are not epoxidized under these conditions. (C) 2010 Published by Elsevier Ltd.