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
metal‐free aerobic oxidative cross‐coupling reaction between a benzylic C(sp3)–H bond and a carboxylic acidcatalyzed by 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone and tert‐butyl nitrite has been developed. This protocol provides a mild and efficient route to obtain diarylmethanol esters and phthalides. It can be regarded as a typical example of green chemistry in oxidative C–O coupling.
DDQ-Catalyzed Oxidative CO Coupling Of sp<sup>3</sup>CH Bonds With Carboxylic Acids
作者:Hong Yi、Qiang Liu、Jie Liu、Ziqi Zeng、Yuhong Yang、Aiwen Lei
DOI:10.1002/cssc.201200458
日期:2012.11
catalytic amounts of DDQ combined with MnO2 as oxidant, an efficient oxidative CO coupling of benzylic sp3 CH bonds with carboxylic acids affords a series of carboxylic esters in 70–98 % yields. A wide range of functional groups and various carboxylic acids are tolerated. The reaction involves both CH functionalization and CO bond formation.
A survey of enoldiazo nucleophilicity in selective C–C bond forming reactions for the synthesis of natural product-like frameworks
作者:Yuxiao Liu、Yu Liu、Charles S. Shanahan、Xichen Xu、Michael P. Doyle
DOI:10.1039/c4ob00709c
日期:——
Sc(OTf)3-catalyzed SN1-like couplings of enoldiazo compounds with carbocations for construction of carbocyclic and heterocyclic scaffolds has been realised.
Herein, a photoredox-neutral strategy for carboxylation of acylated alcohols via C(sp3)–O bond activation and cleavage with tetrabutylammonium oxalate (TBAO) as the carbonyl source and reductant as well as the promoter is described. Neither a pre-established CO2 atmosphere nor external electron donors are required as the TBAO is crucial for the transformation. Various primary, secondary, and tertiary