Catalytic Hydroetherification of Unactivated Alkenes Enabled by Proton‐Coupled Electron Transfer
作者:Elaine Tsui、Anthony J. Metrano、Yuto Tsuchiya、Robert R. Knowles
DOI:10.1002/anie.202003959
日期:2020.7.13
We report a catalytic, light‐driven method for the intramolecular hydroetherification of unactivated alkenols to furnish cyclic ether products. These reactions occur under visible‐light irradiation in the presence of an IrIII‐based photoredox catalyst, a Brønsted base catalyst, and a hydrogen‐atom transfer (HAT) co‐catalyst. Reactive alkoxy radicals are proposed as key intermediates, generated by direct
我们报告了一种催化光驱动方法,用于未活化烯醇的分子内加氢醚化以提供环醚产品。这些反应在 Ir III基光氧化还原催化剂、布朗斯台德碱催化剂和氢原子转移 (HAT) 助催化剂存在下在可见光照射下发生。反应性烷氧基被认为是关键中间体,是通过质子耦合电子转移机制直接均裂激活醇 O−H 键而产生的。该方法表现出广泛的底物范围和高官能团耐受性,并且适应多种烯烃取代模式。还提出了证明该催化系统扩展到碳醚化反应的结果。
Chemo- and stereoselectivity in titanium-mediated regioselective ring-opening reaction of epoxides at the more substituted carbon
Chemo- and stereoselectivity in the ring-openingreaction of epoxides with a reagent prepared from allylmagnesium halide and chlorotitanium triphenoxide is described. It has been proven that the allylating reagent can also be used for the reaction of epoxides bearing a tert-butyl ester, amide, or acetal moiety, and that the epoxide cleavage regioselectively takes place at the more substituted carbon
Dirhodium(II)-Mediated Alkene Epoxidation with Iodine(III) Oxidants
作者:Ali Nasrallah、Gwendal Grelier、Maria Ivana Lapuh、Fernando J. Duran、Benjamin Darses、Philippe Dauban
DOI:10.1002/ejoc.201800306
日期:2018.11.15
combination of the dirhodium(II) complex Rh2(tpa)4 (tpa = triphenylacetate) with the iodine(III) oxidant PhI(OPiv)2 is shown to promote the epoxidation of alkenes in the presence of 2 equivalents of water. The reaction can be applied to diversely substituted alkenes and the corresponding epoxides are isolated with yields of up to 90 %. A possible mechanism involves the dirhodium(II) complex as a Lewis
Dirhodium (II) 络合物和碘 (III) 氧化剂已在合成氮烯化学中找到有用的应用。在这项研究中,二铑(II)配合物 Rh2(tpa)4(tpa = 三苯乙酸盐)与碘(III)氧化剂 PhI(OPiv)2 的组合被证明在 2 当量的水。该反应可应用于不同取代的烯烃,并以高达 90% 的产率分离相应的环氧化物。一种可能的机制涉及二铑 (II) 络合物作为路易斯酸物质,它可以调节碘 (III) 试剂的氧化特性。
Metal- and Reagent-Free Intramolecular Oxidative Amination of Tri- and Tetrasubstituted Alkenes
作者:Peng Xiong、He-Huan Xu、Hai-Chao Xu
DOI:10.1021/jacs.7b01016
日期:2017.3.1
A metal- and reagent-free, electrochemical intramolecularoxidative amination reaction of tri- and tetrasubstituted alkenes has been developed. The electrosynthetic method proceeds through radical cyclization to form the key C-N bond, allowing a variety of hindered tri- and tetrasubstituted olefins to participate in the amination reaction. The result is the efficient synthesis of a host of alkene-bearing
Enantioselective Hydroamination of Alkenes with Sulfonamides Enabled by Proton-Coupled Electron Transfer
作者:Casey B. Roos、Joachim Demaerel、David E. Graff、Robert R. Knowles
DOI:10.1021/jacs.0c01332
日期:2020.4.1
proceed via N-centered radicals formed by proton-coupled electron transfer (PCET) activation of sulfonamide N-H bonds. Non-covalent interactions between the neutral sulfonamidyl radical and a chiral phosphoric acid generated in the PCET event are hypothesized to serve as the basis for asymmetric induction in a subsequent C-N bond forming step, achieving selectivities of up to 98:2 er. These results offer
报道了一种对映选择性、基于自由基的方法,用于烯烃与磺酰胺的分子内加氢胺化。建议这些反应通过磺酰胺 NH 键的质子耦合电子转移 (PCET) 活化形成的 N 中心自由基进行。中性磺酰胺自由基与 PCET 事件中产生的手性磷酸之间的非共价相互作用被假设为后续 CN 键形成步骤中不对称诱导的基础,实现高达 98:2 er 的选择性。这些结果进一步支持了非共价相互作用在瞬态和高反应性开壳中间体的反应中增强立体选择性的能力。