近年来,芳基卤化物和苄基卤化物与 CO2 的羧化取得了重大进展,成为使用化学计量量明确的金属物质的方便替代品。然而,这些过程中的大多数都需要使用自燃和空气敏感试剂,目前的方法主要限于有机卤化物。因此,非常希望发现一种温和的、操作简单的替代羧化反应,该羧化反应在广泛的底物范围内使用容易获得的偶联伙伴发生。在此,我们报告了一种新的协议,该协议涉及 CO2 协同活化的开发和惰性 C(sp(2))-O 和 C(sp(3))-O 键的相当具有挑战性的活化,这些键源自简单且廉价的酒精,这是该领域以前未被认识到的机会。这种前所未有的羧化事件的特点是其简单、温和的反应条件、显着的选择性模式以及使用对空气、水分不敏感且易于处理的镍预催化剂的优异化学选择性曲线。我们的结果使我们的方法成为一种强大的替代方案,实用性和新颖性,可以替代常用的有机卤化物作为羧化方案中的对应物。此外,这项研究首次表明,无痕导向基团允许在没有扩展
[GRAPHICS]The high level of catalyst performance was attainable in the palladium-catalyzed 1,2-addition of aryl-, heteroaryl-, and alkenylboronic acids to aromatic, heteroaromatic, and aliphatic aldehydes using thioether-imidazolinium chloride L5 as a heterobidentate carbene ligand precursor.
Palladium-catalyzed arylation of aldehydes with bromo-substituted 1,3-diaryl-imidazoline carbene ligand
The combination of 0 valent palladium precursor and bromo-substituted 1,3-diaryl-imidazoline carbene ligand precursor such as 1-(2-bromophenyl)-3-(2,6-diisopropylphenyl)-imidazolinium chloride 1a exhibited high catalytic activity for the 1,2-addition of arylboronic acids to aldehydes including aqueous formaldehyde. (C) 2014 Elsevier Ltd. All rights reserved.
Palladium-imidazolinium carbene-catalyzed arylation of aldehydes with arylboronic acids in water
The catalytic arylation of aldehydes with arylboronic acids in only water was found to be achieved using the palladium/thioether-imidazolinium chloride system in good to excellent yields. This catalytic process showed high tolerance for a broad range of substrates, giving a variety of carbinol derivatives with 2.0-3.0 mol % of the catalyst. (C) 2010 Elsevier Ltd. All rights reserved.
Palladium-Catalyzed Stereospecific Decarboxylative Benzylation of Alkynes
作者:Shehani N. Mendis、Jon A. Tunge
DOI:10.1021/acs.orglett.5b02410
日期:2015.11.6
Enantioenriched benzyl esters of propiolic acids undergo highly stereospecific decarboxylative coupling to provide 1,1-diarylethynyl methanes. This sp-sp(3) coupling does not require strongly basic conditions or preformed organometallics and produces CO2 as the sole byproduct. Ultimately, this method results in the successful transfer of stereochemical information from secondary benzyl alcohols to generate enantioenriched tertiary diarylmethanes.
Palladium-Catalyzed 1,2-Addition of Potassium Aryl- and Alkenyltrifluoroborates to Aldehydes using Thioether−Imidazolinium Carbene Ligands
Palladium-catalyzed 1,2-addition of potassium aryl- and alkenyltrifluoroborates to aldehydes using thioether-imidazolinium carbene ligands proceeded readily under aqueous conditions. This process tolerated a diverse range of potassium trifluoroborate salts and aldehydes, giving a variety of carbinol derivatives with good to excellent yields.