Ligand survey results in identification of PNP pincer complexes of iridium as long-lived and chemoselective catalysts for dehydrogenative borylation of terminal alkynes
作者:Chun-I Lee、Jessica C. DeMott、Christopher J. Pell、Alyson Christopher、Jia Zhou、Nattamai Bhuvanesh、Oleg V. Ozerov
DOI:10.1039/c5sc02161h
日期:——
Following the report on the successful use of SiNN pincercomplexes of iridium as catalysts for dehydrogenative borylation of terminal alkynes (DHBTA) to alkynylboronates, this work examined a wide variety of related pincerligands in the supporting role in DHBTA. The ligand selection included both new and previously reported ligands and was developed to explore systematic changes to the SiNN framework
继关于成功使用铱的 SiNN 钳形配合物作为末端炔烃 (DHBTA) 脱氢硼化为炔基硼酸盐的催化剂的报告之后,这项工作研究了各种相关钳形配体在 DHBTA 中的支持作用。配体选择包括新的和以前报道的配体,旨在探索 SiNN 框架(8-(2-二异丙基甲硅烷基苯基)氨基喹啉)的系统变化。令人惊讶的是,只有二芳基氨基/双(膦) PNP 系统显示出任何 DHBTA 反应性。筛选中使用的特定 PNP 配体(带有两个二异丙基膦基侧供体)显示 DHBTA 活性低于 SiNN。然而,利用 PNP 系统提供的配体优化机会,通过磷取代的变化导致发现了一种催化剂,其活性、寿命和范围远远超过了原始 SiNN 原型。在模型 PNP 系统中制备了几种 Ir 配合物,并作为催化循环中的潜在中间体进行了评估。其中,(PNP)Ir 二硼基络合物和硼基亚乙烯基络合物显示出催化能力较差,因此可能不是催化循环的一部分。
Cyclic (Alkyl)(amino)carbene Ligands Enable Cu‐Catalyzed Markovnikov Protoboration and Protosilylation of Terminal Alkynes: A Versatile Portal to Functionalized Alkenes**
作者:Yang Gao、Sima Yazdani、Aaron Kendrick、Glen P. Junor、Taeho Kang、Douglas B. Grotjahn、Guy Bertrand、Rodolphe Jazzar、Keary M. Engle
DOI:10.1002/anie.202106107
日期:2021.9
donating cyclic (alkyl)(amino)carbene (CAAC) ligands. Using this method, both alkyl- and aryl-substituted alkynes are coupled with a variety of boryl and silyl reagents with high α-selectivity. The reaction is scalable, and the products are versatile intermediates that can participate in various downstream transformations. Preliminary mechanistic experiments shed light on the role of CAAC ligands in this
Atroposelective Synthesis of Conjugated Diene-Based Axially Chiral Styrenes via Pd(II)-Catalyzed Thioether-Directed Alkenyl C–H Olefination
作者:Liang Jin、Peng Zhang、Ya Li、Xin Yu、Bing-Feng Shi
DOI:10.1021/jacs.1c06236
日期:2021.8.11
The efficient stereoselective synthesis of conjugated dienes, especially those with axial chirality, remains a great challenge. Herein, we report the highly atroposelective synthesis of axially chiral styrenes with a conjugated 1,3-diene scaffold via a Pd(II)-catalyzed thioether-directed alkenyl C–H olefination strategy. This strategy features easy operation, mild reaction conditions, high functional
Reaction Pathways and Redox States in α‐Selective Cobalt‐Catalyzed Hydroborations of Alkynes
作者:Clemens K. Blasius、Vladislav Vasilenko、Regina Matveeva、Hubert Wadepohl、Lutz H. Gade
DOI:10.1002/anie.202009625
日期:2020.12.14
Cobalt(II) alkyl complexes supported by a monoanionic NNN pincer ligand are pre‐catalysts for the regioselective hydroboration of terminal alkynes, yielding the Markovnikov products with α:β‐(E) ratios of up to 97:3. A cobalt(II) hydride and a cobalt(II) vinyl complex appear to determine the main reaction pathway. In a background reaction the highly reactive hydrido species specifically converts to