Water as a Hydrogenating Agent: Stereodivergent Pd-Catalyzed Semihydrogenation of Alkynes
作者:Chuan-Qi Zhao、Yue-Gang Chen、Hui Qiu、Lei Wei、Ping Fang、Tian-Sheng Mei
DOI:10.1021/acs.orglett.9b00148
日期:2019.3.1
Palladium-catalyzed transfer semihydrogenation of alkynes using H2O as the hydrogen source and Mn as the reducing reagent is developed, affording cis- and trans-alkenes selectively under mild conditions. In addition, this method provides an efficient way to access various cis-1,2-dideuterioalkenes and trans-1,2-dideuterioalkenes by using D2O instead of H2O.
diverse range of functional groups including silyl protections. The silicon residue is readily recovered and reused on a gram-scale synthesis. Intramolecular coordination of a proximal hydroxyl group is considered to efficiently form pentacoordinate silicates having a transferablegroup possibly at an axial position and, thus, responsible for the cross-coupling reaction under conditions significantly
通过使用保护的[2-(羟甲基)苯基]二甲基硅烷,通过铂或钌催化剂催化的炔烃的立体和区域选择性氢化硅烷化反应,制备高度稳定的烯基[2-(羟甲基)苯基]二甲基硅烷。通过与烯基格氏试剂的开环反应,环状甲硅烷基醚1,1-二甲基-2-氧杂-1-silaindan也用作烯基硅烷的原料。在使用K 2 CO 3的反应条件下,所得烯基硅烷与各种芳基和烯基碘化物进行交叉偶联反应以高度区域性和立体定向方式在35–50°C下作为碱。该反应可耐受各种官能团,包括甲硅烷基保护基。硅残留物很容易被回收并以克级合成法再利用。近端羟基的分子内配位被认为有效地形成了可能在轴向位置具有可转移基团的五配位硅酸盐,因此,在比基于硅的反应所报道的条件温和得多的条件下,负责交叉偶联反应。
An Amine-Assisted Ionic Monohydride Mechanism Enables Selective Alkyne <i>cis</i>-Semihydrogenation with Ethanol: From Elementary Steps to Catalysis
protonolysis of the Ir–C(vinyl) bond. Instead, mechanistic data are consistent with an anion-involved alcoholysis pathway involving ionization of (NCP)IrCl(vinyl) via EtOH-for-Cl substitution and reversible protonation of Cl– ion with an Ir(III)-bound EtOH, followed by β-H elimination of the ethoxy ligand and C(vinyl)–H reductive elimination. The use of an amine is key to the monohydride mechanism by promoting
Stereoselective Preparation of Polyfunctional Alkenylindium(III) Halides and Their Cross-Coupling with Unsaturated Halides
作者:Zhi-Liang Shen、Paul Knochel
DOI:10.1002/chem.201500943
日期:2015.5.4
The directinsertion of indium powder to cycloalkenyl iodides in the presence of LiCl in THF allows the preparation of new highly functionalized cycloalkenylindium(III) derivatives. In addition, we discovered that, in contrast to many metal insertions to alkenyl iodides which proceed with a loss of stereochemistry, the insertion of In/LiCl to stereodefined (Z)‐ and (E)‐styryl iodides in THF proceeded
Heterobimetallic Pd/Mn and Pd/Co complexes as efficient and stereoselective catalysts for sequential Cu-free Sonogashira coupling–alkyne semi-hydrogenation reactions
stereoselective semi-hydrogenation of the alkyne intermediate using NH3·BH3 as a hydrogen source. Furthermore, different aromatic substrates have been tested to show the generality of the reaction for the synthesis of Z-alkenes, including biologically active combretastatin A-4. In addition, the homogeneous nature of the catalytically active species was demonstrated.
一系列异质双金属 Pd II /M II配合物 (M II = Mn, Co) 被合成并测试作为顺序 Sonogashira 偶联 - 炔烃半氢化反应形成Z-芳基烯烃的预催化剂。与相应的单金属对应物相比,碳金属化异质双金属 Pd II /Co II配合物CoPdL3'表现出明显的协同效应。该化合物被确定为一种有效的单分子催化剂,用于芳基溴化物与末端炔烃的一锅无铜 Sonogashira 偶联,然后使用 NH 3 ·BH 3对炔烃中间体进行化学和立体选择性半氢化作为氢源。此外,已经测试了不同的芳族底物以显示合成Z-烯烃的反应的普遍性,包括生物活性的考布他汀 A-4。此外,还证明了催化活性物质的均一性。