Enantioselective reduction of ketoxime ethers with borane–oxazaborolidines and synthesis of the key intermediate leading to (S)-rivastigmine
摘要:
The reduction of representative alkyl aryl (E)-ketoxime O-benzyl ethers with borane catalyzed by terpene oxazaborolidines, derived from (1R)-nopinone and (1R)-camphor, gave the corresponding amines with 82-99% ee. Oxazaborolidines derived from (1S)-2-carene and (1S)-3-carene were less selective. (S)-1-(3-Methoxyphenyl)ethanamine (94% ee) the key intermediate in the synthesis of (S)-rivastigmine, was obtained by the reduction of (E)-1-(3-methoxyphenyl)ethanone O-benzyl oxime with borane/oxazaborolidine generated from (S)-valinol. (C) 2012 Elsevier Ltd. All rights reserved.
efficient, reusable and stable binaphthyl stabilized Pd‐nanoparticles (Pd‐BNP) catalyzed the direct ortho‐C−H hydroxylation of acetophenone oxime ethers under neutral and phosphineligand‐free condition has been developed. A readily available, economic, safe and greener oxidant oxone has been used in this direct ortho‐hydroxylation. The scope of the reaction has been studied with various acetophenone oxime
Iridium‐Catalyzed Acid‐Assisted Hydrogenation of Oximes to Hydroxylamines
作者:Josep Mas‐Roselló、Christopher J. Cope、Eric Tan、Benjamin Pinson、Alan Robinson、Tomas Smejkal、Nicolai Cramer
DOI:10.1002/anie.202103806
日期:2021.7.5
stoichiometric amounts of methanesulfonic acid and reduced at room temperature, remarkably without cleavage of the fragile N−O bond. The exquisite functional group compatibility of our hydrogenation system was further demonstrated by additive tests. Experimental mechanistic investigations support an ionic hydrogenation platform, and suggest a role for the Brønstedacid beyond a proton source. Our studies
我们发现环金属化环戊二烯基铱 (III) 配合物是将肟均相氢化成羟胺产物的独特高效催化剂。稳定的铱 C,N 螯合至关重要,烷氧基取代的芳基酮亚胺配体可提供最佳催化性能。通过 X 射线晶体分析绘制了几种 Ir 配合物,以收集空间参数,这些参数可能指导更活性催化剂的合理设计。大量的肟和肟醚被化学计量的甲磺酸活化并在室温下被还原,显着地没有断裂脆弱的 NO 键。添加剂测试进一步证明了我们加氢系统的精细官能团兼容性。实验机理研究支持离子氢化平台,并建议布朗斯台德酸在质子源之外的作用。我们的研究提供了对这种新型酸性氢化的深入理解,并可能促进其改进和应用于其他具有挑战性的底物。
Nickel-catalysed asymmetric hydrogenation of oximes
作者:Bowen Li、Jianzhong Chen、Dan Liu、Ilya D. Gridnev、Wanbin Zhang
DOI:10.1038/s41557-022-00971-8
日期:2022.8
corresponding chiral hydroxylamines remains challenging because of the labile N–O bond and inert C=N bond. Here we report an environmentally friendly, earth-abundant, transition-metal nickel-catalysed asymmetric hydrogenation of oximes, affording the corresponding chiral hydroxylamines with up to 99% yield, 99% e.e. and with a substrate/catalyst ratio of 1,000. Computational results indicate that the weak interactions