The Proline-Catalyzed Asymmetric Amination of Branched Aldehydes
作者:Thomas Baumann、Henning Vogt、Stefan Bräse
DOI:10.1002/ejoc.200600654
日期:2007.1
An efficient access to configurationally stable α,α-disubstituted α-amino aldehydes, oxazolidinones, and α-amino acids has been presented. Starting from simple and easily available racemic aldehydes, the α-aminated products were obtained using azodicarboxylates as the nitrogen source in up to 86 % ee and moderate to excellent yield. These products could further be converted both into the corresponding
Copper-Catalyzed Vinylogous Aerobic Oxidation of Unsaturated Compounds with Air
作者:Hai-Jun Zhang、Alexander W. Schuppe、Shi-Tao Pan、Jin-Xiang Chen、Bo-Ran Wang、Timothy R. Newhouse、Liang Yin
DOI:10.1021/jacs.8b01886
日期:2018.4.18
A mild and operationally simple copper-catalyzed vinylogous aerobic oxidation of β,γ- and α,β-unsaturated esters is described. This method features good yields, broad substrate scope, excellent chemo- and regioselectivity, and good functional group tolerance. This method is additionally capable of oxidizing β,γ- and α,β-unsaturated aldehydes, ketones, amides, nitriles, and sulfones. Furthermore, the
描述了一种温和且操作简单的铜催化乙烯基有氧氧化 β,γ-和 α,β-不饱和酯。该方法具有收率好、底物范围广、化学选择性和区域选择性好、官能团耐受性好等特点。该方法还能够氧化β,γ-和α,β-不饱和醛、酮、酰胺、腈和砜。此外,本催化体系适用于双乙烯基和三乙烯基氧化。发现四甲基胍 (TMG) 作为碱的作用至关重要,但我们也推测它可以作为三氟甲磺酸铜 (II) 的配体来生产活性铜 (II) 催化剂。进行的机械实验表明,通过烯丙基铜 (II) 物质存在一个合理的反应途径。最后,
Pummerer Cyclization Revisited: Unraveling of Acyl Oxonium Ion and Vinyl Sulfide Pathways
作者:Xin Li、Rich G. Carter
DOI:10.1021/acs.orglett.8b02059
日期:2018.9.21
Two viable pathways (vinyl sulfide and acyl oxoniumion) for the Pummerer cyclization have been unraveled that expand the reaction scope and capabilities. Use of Brønsted-enhanced Lewis acidity was key to realization of the vinyl sulfide pathway, whereas selective complexation of the sulfur lone pair facilitated the unprecedented acyl oxoniumion pathway. Preliminary mechanistic investigations support
The first nickel-catalyzed desymmetric hydrogenation has been achieved. With the Ni(OTf)2/(S,S)-Ph-BPE system, a series of γ,γ-disubstituted cyclohexadienones were transformed to the corresponding cyclohexenones with a chiral all-carbon quaternary center at the γ position in high yields (92% to 98%) and excellent enantioselectivities (92% to 99% ee). This catalytic system can also tolerate the desymmetric
首次实现了镍催化的不对称氢化。使用 Ni(OTf)2/(S,S)-Ph-BPE 系统,一系列 γ,γ-二取代环己二烯酮以高产率转化为相应的环己烯酮,其在 γ 位具有手性全碳四元中心( 92% 至 98%)和出色的对映选择性(92% 至 99% ee)。该催化体系还可以耐受螺碳环环己二烯酮的去对称反应,以产生相应的带有手性螺季碳的环己烯酮,收率高(94% 至 98%)和 ee 值(96% 至 99% ee)。此外,该方法为天然产物大麻吡酮 A 和 B 的中间体提供了一种高效、简洁的合成路线。
KO‐
<i>t</i>
‐Bu Catalyzed Thiolation of
<i>β</i>
‐(Hetero)arylethyl Ethers via MeOH Elimination/hydrothiolation
We describe a KO-t-Bu catalyzedthiolation of β-(hetero)arylethylethers through MeOHelimination to form (hetero)arylalkenes followed by anti-Markovnikov hydrothiolation to afford linear thioethers. The system works well with a variety of β-(hetero)arylethylethers, including electron-deficient, electron-neutral, electron-rich, and branched substrates and a range of aliphatic and aromatic thiols.
我们描述了 KO- t- Bu 催化的β-(杂)芳基乙基醚通过 MeOH 消除形成(杂)芳基烯烃的硫醇化反应,然后进行反马尔可夫尼科夫氢硫醇化反应以提供线性硫醚。该系统适用于各种β-(杂)芳基乙基醚,包括缺电子、电子中性、富电子和支化底物以及一系列脂肪族和芳香族硫醇。