Aluminum Complexes of Monopyrrolidine Ligands for the Controlled Ring-Opening Polymerization of Lactide
作者:James Beament、Mary F. Mahon、Antoine Buchard、Matthew D. Jones
DOI:10.1021/acs.organomet.8b00161
日期:2018.6.11
In this paper we report the full characterization (solution-state NMR spectroscopy and solid-state structures) of a series of Al(III) half-salan complexes and their exploitation for the ring-openingpolymerization of rac-lactide. Depending on the ligand employed and stoichiometry of the complexation, structures of the form Al(X)2Me or Al(X)Me2 were isolated. Interestingly Al(2)2Me and Al(2)Me2 produce
Electrochemical and Homogeneous Proton-Coupled Electron Transfers: Concerted Pathways in the One-Electron Oxidation of a Phenol Coupled with an Intramolecular Amine-Driven Proton Transfer
Proton-coupled electrontransfers currently attract considerable attention in view of their likely involvement in many natural processes. Electrochemistry, through techniques such as cyclic voltammetry, is an efficient way of investigating the reaction mechanism of these reactions, and deciding whether proton and electrontransfers are concerted or occur in a stepwise manner. The oxidation of an ortho-substituted
鉴于它们可能参与许多自然过程,质子耦合电子转移目前引起了相当大的关注。电化学,通过循环伏安法等技术,是研究这些反应的反应机理,并确定质子和电子转移是否协调或逐步发生的有效方法。以邻位取代的 4,6-二(叔丁基)-苯酚的氧化为例,其中酚氢原子在反应过程中转移到附近胺的氮原子上。对该化合物及其 OD 衍生物获得的循环伏安响应的仔细分析允许在估计各种热力学参数后,排除涉及质子 - 电子和电子 - 质子序列的平方方案机制的发生。速率常数和 H/D 动力学同位素效应与理论预测的模拟和比较表明,指前因子的实验值约为。比理论值大1个数量级。详细的计算表明,电场效应是造成这种差异的原因。
Efficient One-Pot Synthesis of Propargylamines from Mannich Bases through a Retro-Mannich-Type Fragmentation
作者:Yunyang Wei、Yefeng Zhu、Huishuang Zhao
DOI:10.1055/s-0032-1316862
日期:——
An efficient one-pot synthesis of propargylamines is achieved by copper-catalyzed coupling of phenylacetylenes with Mannich bases through a chlorine(1+) or bromine(1+) ion-initiated retro-Mannich-type fragmentation under mild conditions. The Mannich bases are easily prepared from an electron-rich phenol, formaldehyde, and an amine. The protocol provides an appealing alternative for the construction of propargylamines by a simple one-pot procedure.
Monocyclopentadienyl phenoxy-imine and phenoxy-amine complexes of titanium and zirconium and their application as catalysts for 1-alkene polymerisation
作者:Robyn K.J Bott、David L Hughes、Mark Schormann、Manfred Bochmann、Simon J Lancaster
DOI:10.1016/s0022-328x(02)02106-x
日期:2003.1
Deprotonation of the phenol-imines 2-Bu'-6-(RNCH)C6H3OH (R = 2,4,6-Me3C6H2 (1a), C6F5 (1b), C6H11 (1c) and phenolamines 2,4-Bu'(2)-6-(R'NCH2)C6H2OH (R' = C4H8 (1d), C5H10 (1e)) with n -BuLi gives the corresponding lithium phenoxides. The reaction with MCl4 in THF solution leads to the bis(ligand) complexes 2-Bu'-6-(RNCH)C6H3H3O}(2)MCl2 and 2,4-Bu'(2)-6-(R'NCH2)C6H2O}(2)MCl2 (M=Ti: 2a, 2d, 2e, Zr: 3a, 3d and 3e). The cyclopentadienyl phenoxy-imine and -amine complexes Cp2-Bu'-6-(RNCH)C6H3O}MCl2 and Cp2,4-Bu'(2)-6-(R'NCH2)C6H2O}MCl2 (M = Ti: 4a-4e, Zr: 5a-5e) were prepared similarly through reaction with CPMCl3. The crystal and molecular structures of 2a, 3a, 4a and 4c have been determined. 2a and 3a are isostructural and exhibit a distorted octahedral geometry. 4a has a distorted square-pyramidal structure whereas 4e is essentially tetrahedral and the nitrogen does not coordinate. All new complexes are active for the polymerisation of ethene when activated with methyaluminoxane. 4b, 5a, 5d and 5e are active for the copolymerisation of ethene and 1-hexene and the oligomerisation of 1-hexene. (C) 2002 Elsevier Science B.V. All rights reserved.
Construction of Persistent Phenoxyl Radical with Intramolecular Hydrogen Bonding