Ligand‐Controlled Palladium‐Catalyzed
Regiodivergent Defluorinative Allylation of
gem
‐Difluorocyclopropanes
via
σ‐Bond
Activation
摘要:
Comprehensive SummaryMonofluoroalkenes are important and versatile privileged components in pharmacologically relevant molecules. Here, we report a method for the selective construction of these compounds in a diversity‐oriented fashion through regiodivergent cross‐coupling of gem‐difluorocyclopropanes with allylboronates by employing a palladium catalyst with two different ligands, in which gem‐difluorocyclopropanes were used as allyl electrophiles by C—C and C—F bond activation. In the presence of 2‐biphenylyl(diphenyl)phosphine as ligand, the linear‐selective allyl–allyl bond formation is highly obtained, while utilizing the sterically hindered BrettPhos (dicyclohexyl[3,6‐dimethoxy‐2',4',6'‐tris(1‐methylethyl)[1,1'‐biphenyl]‐2‐yl]phosphine) as the ligand favors the generation of the branched‐selective product. Experimental and computational studies investigated the key steps of the cross‐coupling reactions, revealing the origin of the ligand‐controlled regiodivergence.
mild visible light-induced palladium-catalyzed alkyl Heckreaction of diazo compounds and N-tosylhydrazones is reported. This method features Brønsted acid assisted generation of hybrid palladium C(sp3)-centered radical intermediate and broad reaction scope, highlighting the diverse applicability and the potential utility of this protocol in late-stage functionalization.
A Neutral Metal-Free System for Head-to-Tail Dimerization of Electron-Rich Alkenes
作者:A-Yun Luo、Yan Bao、Xiu-Fen Cheng、Xi-Sheng Wang
DOI:10.1055/s-0036-1589039
日期:2017.9
Abstract A neutral metal-free system for the head-to-tail dimerization of electron-rich alkenes with stoichiometric amount of BrCCl2H and NaI is reported. This reaction proceeds under mild conditions with high efficiency and broad scope. A neutral metal-free system for the head-to-tail dimerization of electron-rich alkenes with stoichiometric amount of BrCCl2H and NaI is reported. This reaction proceeds
A Straightforward Route to Potent Phenolic Chain‐Breaking Antioxidants by Acid‐Promoted Transposition of 1,4‐Benzo[
<i>b</i>
]oxathiines to Dihydrobenzo[
<i>b</i>
]thiophenes
作者:Caterina Viglianisi、Riccardo Amorati、Leonardo Di Pietro、Stefano Menichetti
DOI:10.1002/chem.201502650
日期:2015.11.9
The transformation of simple phenols with limited antioxidant activity into potentchain‐breakingantioxidants was achieved by a three‐step protocol, consisting of the conversion of phenols into 1,4‐benzo[b]oxathiines followed by an unprecedented acid‐promotedtransposition to o‐hydroxydihydrobenzo[b]thiophenes, or dihydrobenzo[de]thiochromenes, starting from phenols or naphthols, respectively. These
将抗氧化剂活性有限的简单酚类转化为有效的链断裂抗氧化剂,可通过三步操作完成,包括将酚类转化为1,4-苯并[ b ]恶二环烷,然后再进行前所未有的酸促成转位为邻位。 -羟基二氢苯并[ b ]噻吩或二氢苯并[ de ]噻吩,分别从酚或萘酚开始。这些衍生物,轴承与硫醚硫苯并稠合的杂环邻位的酚OH,具有反应与烷基过氧自由基的速率常数(ķ INH)与α-生育酚相当 提出了关于转座机理以及结构与抗氧化剂活性关系的坚实原理。
Cobalt-Catalyzed<i>Z</i>to<i>E</i>Isomerization of Alkenes: An Approach to (<i>E</i>)-β-Substituted Styrenes
An efficient cobalt-catalyzed Z to E isomerization of β-substituted styrenes using the amido-diphosphine ligand was developed, delivering the (E)-isomers with good functional tolerance and high stereoselectivity. The reaction could be scaled up to gram-scale with a catalyst loading of 0.1 mol %, using a mixture of (Z)- and (E)-alkene as the starting material. Preliminary mechanistic studies indicated
Manganese-Catalyzed Redox-Neutral C−H Olefination of Ketones with Unactivated Alkenes
作者:Yuanyuan Hu、Bingwei Zhou、Hui Chen、Congyang Wang
DOI:10.1002/anie.201806287
日期:2018.9.10
presence of either palladium salts or trimethylamine N‐oxide (Me3N+O−) have been reported, but the catalytic versions remain untouched so far. Herein, the first manganese‐catalyzed redox‐neutral C−H olefination of ketones with unactivated alkenes is described, and shows a distinct reactivity with its parent stoichimetric reactions. Remarkably, mechanistic experiments and DFTcalculations uncovers a unique