Highly chemoselective palladium-catalyzed conjugate reduction of .alpha.,.beta.-unsaturated carbonyl compounds with silicon hydrides and zinc chloride cocatalyst
作者:Ehud. Keinan、Noam. Greenspoon
DOI:10.1021/ja00283a029
日期:1986.11
experiments and 'H NMR studies, a catalytic cycle is postulated in which the first step involves reversible coordination of the palladium complex to the electron-deficient olefin and oxidative addition of silicon hydride to form a hydridopalladium olefin complex. Migratory insertion of hydride into the coordinated olefin produces an intermediate palladium enolate which, via reductive elimination, collapses back
由可溶性钯催化剂、氢化硅烷和氯化锌组成的三组分体系能够有效地共轭还原α、不饱和酮和醛。最佳条件组包括二苯基硅烷作为最有效的氢化物供体,任何可溶于 0 或 I1 氧化态的钯配合物,当它被膦配体稳定时,以及作为最佳路易斯酸助催化剂的 ZnCl。该反应对于范围广泛的不饱和酮和醛非常普遍,并且对于这些迈克尔受体具有高度选择性,因为在这些条件下α,-不饱和羧酸衍生物的还原非常缓慢。当双氘代二苯基硅烷用于还原不饱和酮时,氘在底物的受阻较少的面上立体选择性地引入,并在 8 位上以区域选择性的方式引入。相反,当在痕量 D2O 存在下进行还原时,氘掺入发生在 a 位。在掺入氘的实验和 1 H NMR 研究的基础上,假定催化循环,其中第一步涉及钯配合物与缺电子烯烃的可逆配位和氢化硅的氧化加成以形成氢化钯烯烃配合物。氢化物迁移插入配位的烯烃产生中间体烯醇钯,通过还原消除,它塌缩回 Pd(0) 络合物和甲硅烷基烯
Photocontrolled Cobalt Catalysis for Selective Hydroboration of α,β‐Unsaturated Ketones
作者:Frédéric Beltran、Enrico Bergamaschi、Ignacio Funes‐Ardoiz、Christopher J. Teskey
DOI:10.1002/ange.202009893
日期:2020.11.16
In this way, we bias the reaction down two divergent pathways, giving contrasting products in the catalytic hydroboration of α,β‐unsaturated ketones. This includes direct access to previously elusive cyclic enolborates, via 1,4‐selective hydroboration, providing a straightforward and stereoselective route to rare syn‐aldol products in one‐pot. DFT calculations and mechanistic experiments confirm two
Methylene-Linked Bis-NHC Half-Sandwich Ruthenium Complexes: Binding of Small Molecules and Catalysis toward Ketone Transfer Hydrogenation
作者:José Manuel Botubol-Ares、Safa Cordón-Ouahhabi、Zakaria Moutaoukil、Isidro G. Collado、Manuel Jiménez-Tenorio、M. Carmen Puerta、Pedro Valerga
DOI:10.1021/acs.organomet.1c00045
日期:2021.3.22
isolation of the nitrosyl derivative [Cp*Ru(NO)(L)][BPh4]2 (5), which was structurally characterized. The allenylidene complex [Cp*Ru═C═C═CPh2(L)][BPh4] (10) was also obtained, and it was prepared by reaction of 2 with HC≡CC(OH)Ph2 and NaBPh4 in MeOH at 60 °C. Complexes 3, 4, and 6 are efficient catalyst precursors for the transferhydrogenation of a broad range of ketones. The dihydrogen complex 6 has
Hydrogenation of Carbonyl Derivatives Catalysed by Manganese Complexes Bearing Bidentate Pyridinyl-Phosphine Ligands
作者:Duo Wei、Antoine Bruneau-Voisine、Téo Chauvin、Vincent Dorcet、Thierry Roisnel、Dmitry A. Valyaev、Noël Lugan、Jean-Baptiste Sortais
DOI:10.1002/adsc.201701115
日期:2018.2.15
Manganese(I) catalysts incorporating readily available bidentate 2‐aminopyridinyl‐phosphine ligands achieve a high efficiency in the hydrogenation of carbonyl compounds, significantly better than parent ones based on more elaborated and expensive tridentate 2,6‐(diaminopyridinyl)‐diphosphine ligands. The reaction proceeds with low catalyst loading (0.5 mol%) under mild conditions (50 °C) with yields
Enantio- and regioselective <i>ene</i>-reductions using F<sub>420</sub>H<sub>2</sub>-dependent enzymes
作者:Sam Mathew、Milos Trajkovic、Hemant Kumar、Quoc-Thai Nguyen、Marco W. Fraaije
DOI:10.1039/c8cc04449j
日期:——
In the past decade it has become clear that many microbes harbor enzymes that employ an unusual flavin cofactor, the F420 deazaflavin cofactor. Herein we show that F420-dependent reductases (FDRs) can successfully perform enantio-, regio- and chemoselective ene-reductions. For the first time, we have demonstrated that F420H2-driven reductases can be used as biocatalysts for the reduction of α,β-unsaturated
在过去的十年中,很明显,许多微生物都带有使用不常见的黄素辅助因子F 420去氮黄素辅助因子的酶。本文中,我们显示了依赖F 420的还原酶(FDR)可以成功地进行对映体,区域和化学选择性烯的还原。首次,我们证明了F 420 H 2驱动的还原酶可用作生物催化剂,以良好的转化率(> 99%)以及优异的区域选择性和对映体过量(> 99)还原α,β-不饱和酮和醛。 %ee)。值得注意的是,与公认的FMN依赖的旧黄色酶(OYE)相比,FDR通常显示相反的对映选择性。