Reaction Conditions for the Regiodivergent Direct Arylations at C2‐ or C5‐Positions of Oxazoles using Phosphine‐Free Palladium Catalysts
作者:Xinzhe Shi、Jean‐François Soulé、Henri Doucet
DOI:10.1002/adsc.201900641
日期:2019.10.22
The higher reactivity of C5‐H bond of oxazole as compared to the C2‐H bond in the presence of Pd(OAc)2/KOAc system is consistent with a concerted metalation deprotonation mechanism; whereas the C2‐arylation likely occurs via a simple base deprotonation of the oxazole C2‐position. Then, from these C2‐ or C5‐arylated oxazoles, a second palladium‐catalyzed direct C−H bond arylation affords 2,5‐diaryloxazoles
据报道,恶唑的C 2或C 5的区域直接芳基化有两个反应条件。在这两种情况下,均使用无膦催化剂和廉价的碱,从而以中等至高收率获得芳基化的恶唑。使用Pd(OAc)2 / KOAc作为催化剂和碱,可观察到区域选择性C5-芳基化;而使用Pd(acac)2 / Cs 2 CO 3系统,芳基化发生在恶唑的C2位。与存在Pd(OAc)2 / KOAc系统时的C2-H键相比,恶唑的C5-H键具有更高的反应活性,这与协同的金属化去质子化机理是一致的。而C2芳基化可能是通过恶唑C2位的简单碱基去质子化。然后,从这些C2或C5芳基恶唑中,进行第二次钯催化的直接C H键芳基化,得到具有两个不同芳基的2,5-二芳基恶唑。我们还通过三个CH键功能化步骤将这些顺序的芳基化反应用于2-芳基菲[9,10- d ]恶唑的直接合成。还描述了2-芳基恶唑的芳基单元的Ru催化的CH芳基化。
Direct C–H Bond Arylation of (Benzo)oxazoles with Aryl Chlorides Catalyzed by <i>N</i>-Heterocyclic Carbene–Palladium(II)–1-Methylimidazole Complex
The direct C-H bond arylation of (benzo)oxazoles with aryl chlorides was achieved catalyzed by a well-defined NHC-Pd(II)-Im complex. Under the optimal conditions, various aryl chlorides were successfully applied as the arylating reagents to achieve the 2-aryl (benzo)oxazoles in acceptable to high yields, providing a convenient and alternative method for the direct C-H bond arylation of (benzo)oxazoles and enriching the chemistry of the NHC-Pd(II) complex in organic synthesis.
Orientation effects on C2(5)-C2ʹ(5ʹ) linked bioxazole isomers synthesized via regioselective and sequential C H arylation
作者:Qiang Guo、Li Tao、Chuanqi Liu、Xiaoyun Zhao、Danyang Wan、Jincheng Zhang、Jianping Ai、Jie Li
DOI:10.1016/j.cclet.2020.05.010
日期:2021.1
THERMALLY ACTIVATED DELAYED FLUORESCENCE CHROMOPHORES AND ORGANIC LAYERS INCLUDING THE SAME
申请人:Wright State University
公开号:US20200131436A1
公开(公告)日:2020-04-30
Thermally activated delayed fluorescence chromophores may comprise a donor ligand, an acceptor ligand, and an acceptor tuner ligand. The donor ligand may be selected from one or more of carbazole, diphenylamine, phenothiazine, phenoxazine, or acridine. The acceptor ligand may be selected from one or more of benzoxazole, benzothiazole, or diphenyl sulfone. The acceptor tuner ligand may comprise a benzene ring. The benzene ring may be at least partially substituted. Organic layers, such as polymers or films, comprising the thermally activated delayed fluorescence chromophores are also disclosed.
Iodine catalysed intramolecular C(sp<sup>3</sup>)–H functionalization: synthesis of 2,5-disubstituted oxazoles from N-arylethylamides
Iodine catalyzed synthesis of 2,5-substituted oxazoles from N-arylethylamides through intramolecular C(sp3)–H functionalization under metal-free conditions is described.