Base-Catalyzed Aryl-B(OH)<sub>2</sub> Protodeboronation Revisited: From Concerted Proton Transfer to Liberation of a Transient Aryl Anion
作者:Paul A. Cox、Marc Reid、Andrew G. Leach、Andrew D. Campbell、Edward J. King、Guy C. Lloyd-Jones
DOI:10.1021/jacs.7b07444
日期:2017.9.20
Pioneering studies by Kuivila, published more than 50 years ago, suggested ipso protonation of the boronate as the mechanism for base-catalyzed protodeboronation of arylboronic acids. However, the study was limited to UV spectrophotometric analysis under acidic conditions, and the aqueous association constants (Ka) were estimated. By means of NMR, stopped-flow IR, and quenched-flow techniques, the
Kuivila于50年前发表的开创性研究表明,硼酸酯的ipso质子化是芳基硼酸的碱催化原脱硼硼烷的机理。但是,该研究仅限于酸性条件下的紫外分光光度法分析,并且估计了水的缔合常数(K a)。借助于NMR,停止流IR和骤冷流技术,现在已经在70°C的二恶烷水溶液中,在pH> 13的条件下,测定了30种不同的芳基硼酸的碱催化原硼酸脱氢反应的动力学。研究中包括C 6 H n F (5- n) B(OH)2的所有20个异构体半衰期跨越9个数量级:<3毫秒至6.5个月。在具有pH率分布,对组合ķ一个和Δ小号⧧值,动力学同位素效应(2 H,10 B,13 C),线性自由能的关系,并密度泛函理论计算,我们已经确定,涉及一种机械制度硼酸酯的单分子杂化与协同的ipso质子化/ C–B裂解竞争。芳基硼酸的相对路易斯酸度与它们的原脱硼氢硼酸速度不相关,特别是当存在邻位取代基时。值得注意的是,3,5-二硝基苯基硼酸
Sodium Diisopropylamide in Tetrahydrofuran: Selectivities, Rates, and Mechanisms of Arene Metalations
作者:Russell F. Algera、Yun Ma、David B. Collum
DOI:10.1021/jacs.7b08734
日期:2017.10.25
Sodium diisopropylamide (NaDA)-mediated metalations of arenes in tetrahydrofuran (THF)/hexane or THF/Me2NEt solutions are described. A survey of >40 benzenoid- and pyridine-based arenes with a range of substituents demonstrates the efficacy and regioselectivity of metalation. Metalations of activated disubstituted arenes and selected monosubstituted arenes are rapid at −78 °C. Rate studies of 1,3-dimethoxybenzene
描述了在四氢呋喃(THF)/己烷或THF / Me 2 NEt溶液中,二异丙基氨基钠(NaDA)介导的芳烃金属化。对超过40种具有一系列取代基的基于苯并吡啶和吡啶的芳烃的研究表明,其金属化的功效和区域选择性都很高。活化的二取代的芳烃和选定的单取代的芳烃在-78°C时快速金属化。1,3-二甲氧基苯和相关甲氧基化芳烃的速率研究表明,基于单体的原金属具有两个或三个配位的THF配体。苯和具有弱活化基团的单取代芳烃的同位素交换速率研究表明,类似的二溶剂化和三溶剂化的单体基金属化反应。讨论了协同的诱导,消旋,空间和螯合作用。
Selective deuteration of (hetero)aromatic compounds via deutero-decarboxylation of carboxylic acids
mild and highly selective protocol for the monodeuteration of a variety of arenes and heteroarenes is presented. Catalytic amounts of Ag(I) salts in DMSO/D2O are shown to facilitate the deutero-decarboxylation of ortho-substituted benzoic and heteroaromatic α-carboxylic acids in high yields with excellent levels of deuterium incorporation.
提出了一种实用,温和且高度选择性的方案,用于多种芳烃和杂芳烃的单氘化。催化量的Ag(I)盐在二甲基亚砜已显示出/ D 2 O以高收率和良好的氘掺入水平促进了邻位取代的苯甲酸和杂芳族α-羧酸的氘代脱羧。
Direct Arylation of Simple Arenes with Aryl Bromides by Synergistic Silver and Palladium Catalysis
作者:Adrian Tlahuext-Aca、Sarah Yunmi Lee、Shu Sakamoto、John F. Hartwig
DOI:10.1021/acscatal.0c05254
日期:2021.2.5
The direct, catalytic arylation of simple arenes in small excess with aryl bromides is disclosed. The developed method does not require the assistance of directing groups and relies on a synergistic catalytic cycle in which phosphine-ligated silver complexes cleave the aryl C–H bond, while palladium catalysts enable the formation of the biaryl products. Mechanistic experiments, including kinetic isotope