Enantioselective Copper(I)/Chiral Phosphoric Acid Catalyzed Intramolecular Amination of Allylic and Benzylic C−H Bonds
作者:Liu Ye、Yu Tian、Xiang Meng、Qiang‐Shuai Gu、Xin‐Yuan Liu
DOI:10.1002/anie.201911742
日期:2020.1.13
radical-involved enantioselective intramolecular C(sp3 )-H amination of not only allylic positions but also benzylic positions with broad substrate scope. The use of 4-methoxy-NHPI (NHPI=N-hydroxyphthalimide) as a stable and chemoselective HAT mediator precursor is crucial for the fulfillment of this transformation. Preliminary mechanistic studies indicate that a crucial allylic or benzylic radical intermediate
Diagnostic fragmentations of adducts formed between carbanions and carbon disulfide in the gas phase. A joint experimental and theoretical study
作者:Micheal J. Maclean、Scott Walker、Tianfang Wang、Peter C. H. Eichinger、Patrick J. Sherman、John H. Bowie
DOI:10.1039/b916477d
日期:——
react with carbondisulfide in a modified LCQ ion trap mass spectrometer to form adducts, which when collisionally activated, decompose by processes which in some cases identify the structures of the original carbanions. For example (i) C6H5− + CS2→ C6H5CS2−→ C6H5S− + CS, occurs through a 3-membered ring ipso transition state, and (ii) the reaction between C6H5CH2− and CS2 gives an adduct which loses
Nickel‐Catalyzed Electrochemical Reductive Relay Cross‐Coupling of Alkyl Halides to Aryl Halides
作者:Ke‐Jin Jiao、Dong Liu、Hong‐Xing Ma、Hui Qiu、Ping Fang、Tian‐Sheng Mei
DOI:10.1002/anie.201912753
日期:2020.4.16
A highly regioselective Ni-catalyzed electrochemical reductive relay cross-coupling between an aryl halide and an alkylhalide has been developed in an undivided cell. Various functional groups are tolerated under these mild reaction conditions, which provides an alternative approach for the synthesis of 1,1-diarylalkanes.
Use of Kinetic Isotope Effects in Mechanism Studies. 5.<sup>1</sup> Isotope Effects and Element Effects Associated with Hydron-Transfer Steps during Alkoxide-Promoted Dehydrohalogenations
作者:Heinz F. Koch、Gerrit Lodder、Judith G. Koch、David J. Bogdan、Geoffrey H. Brown、Carrie A. Carlson、Amy B. Dean、Ronald Hage、Patrick Han、Johan C. P. Hopman、Lisa A. James、Petra M. Knape、Eric C. Roos、Melissa L. Sardina、Rachael A. Sawyer、Barbara O. Scott、Charles A. Testa、Steven D. Wickham
DOI:10.1021/ja970189n
日期:1997.10.1
halide, . Isotopeeffects at 25 °C for I, (kH/kD)Obs = 3.40 and (kH/kT)Obs = 6.20, and II, (kH/kD)Obs = 3.49 and (kH/kT)Obs = 6.55, result in similar values for a: aH = 0.59, aD = 0.13−0.14 and aT = 0.07. Smaller values of (kH/kD)Obs = 2.19 and (kH/kT)Obs = 3.56 for III are due to more internal return [aH = 1.9, aD = 0.50, and aT = 0.28] associated with the dehydrofluorination reaction. Calculation of k1
主要动力学同位素效应 (kH/kD)Obs 和 (kH/kT)Obs 的 Arrhenius 行为,与甲醇钠促进的 m-ClC6H4CiHClCH2Cl (I)、m-CF3C6H4CiHClCH2Cl (II) 和 p- CF3C6H4CiHClCH2F (III) 已被用于计算内部返回参数 a = k-1/ ,采用氢键碳负离子的两步机制。这种碳负离子在将氢返回碳 k-1 和卤化物损失之间分配。同位素效应在 25 °C 时对 I (kH/kD)Obs = 3.40 和 (kH/kT)Obs = 6.20,以及 II (kH/kD)Obs = 3.49 和 (kH/kT)Obs = 6.55,导致a 的相似值:aH = 0.59,aD = 0.13−0.14 和 aT = 0.07。III 的 (kH/kD)Obs = 2.19 和 (kH/kT)Obs = 3.56 的较小值是由于与脱氟化氢反应相关的更多内部回报
Micellar catalysed elimination reactions of p-substituted phenethyl bromides and related compounds in alkaline solutions
dehydrobromination of para-substituted β-phenethyl bromides (3) were determined in alkaline solutions under micellar (kψ) and non-micellar (k0) conditions by using hexadecyltrimethylammonium bromide (1) and di-methyl-(2-hydroxyethyl)octadecylammonium chloride (2) as the micellar surfactants. Large micellar effects (kψ/k0) were observed. Good Hammett relationships were obtained for both kψ and k0 with σp– constants
的脱溴化氢的速率对-取代的β苯乙基溴化物(3)在碱性溶液下胶束(测定ķ ψ)和非胶束(ķ 0)通过使用十六烷基三甲基溴(1)和二甲基-条件(2-羟乙基)十八烷基氯化铵(2)作为胶束表面活性剂。大胶束效果(ķ ψ / ķ 0)观察。得到了良好的哈米特关系两者ķ ψ和ķ 0与σ p -常数。相当大的同位素效应(k H / k D= 8-9)也两个观察ķ ψ和ķ 0。结果表明,与非胶束条件相比,在胶束条件下过渡态更像碳负离子。但是,未检测到起始溴化物与溶剂水的H-D交换,这表明消除前会形成碳负离子。