Alkynes to (E)-enolates using tandem catalysis: stereoselective anti-aldol and syn-[3,3]-rearrangement reactions
摘要:
A new tandem catalysis strategy that transforms alkyne derivatives to (E)-enol-equivalents followed by stereoselective anti-selective aldol coupling or syn-selective [3,3]-rearrangement transformations is reported. The mechanism is thought to proceed through an interchanging series of Lewis acid and Bronsted acid catalyzed reactions via the intermediacy of a ketiminum ion species. (C) 2010 Elsevier Ltd. All rights reserved.
Radical Germylzincation of α-Heteroatom-Substituted Alkynes
作者:Karen de la Vega-Hernández、Elise Romain、Anais Coffinet、Kajetan Bijouard、Geoffrey Gontard、Fabrice Chemla、Franck Ferreira、Olivier Jackowski、Alejandro Perez-Luna
DOI:10.1021/jacs.8b09851
日期:2018.12.19
The regio- and stereoselectiveaddition of germanium and zinc across the C-C triple bond of nitrogen-, sulfur-, oxygen-, and phosphorus-substituted terminal and internal alkynes is achieved by reaction with a combination of R3GeH and Et2Zn. Diagnostic experiments support a radical-chain mechanism and the β-zincated vinylgermanes that show exceptional stability are characterized by NMR spectroscopy
通过与 R3GeH 和 Et2Zn 的组合反应,锗和锌在氮、硫、氧和磷取代的末端和内部炔烃的 CC 三键上的区域和立体选择性加成。诊断实验支持自由基链机制,并通过 NMR 光谱和 X 射线晶体学表征显示出异常稳定性的 β-锌化乙烯基锗烷。这种新的自由基锗基锌化反应的独特之处在于,形成的 C(sp2)-Zn 键仍然可用于随后的原位 Cu(I)-或 Pd(0)-介导的 CC 或 C-杂原子键的形成,同时保留双键几何。
Synthesis of Dibenzoxazonines by Domino [2+2] Cycloaddition—4π Electrocyclic Ring Opening Reaction of Cyclic Imines with Ynamides
4]oxazonines and the thiazonine congener were synthesized from cyclicimines with ynamides by acid-mediated domino (2+2) cycloaddition—4 electrocyclic ring opening reaction. The reaction enables two carbon-enlargement of the cyclicimine substrates. The X-Ray crystallography made clear that the oxazonine skeleton has a unique bent-conformation. Benzo-fused heterocyclic compounds have gathered much attention
二苯并[b,h][1,4]恶唑啉和噻唑啉同源物是由环亚胺与炔酰胺通过酸介导的多米诺(2+2)环加成—4电环开环反应合成的。该反应能够使环状亚胺底物进行两次碳扩增。X 射线晶体学清楚地表明,恶唑啉骨架具有独特的弯曲构象。苯并稠合杂环化合物在药物化学和合成化学领域备受关注。尽管苯并稠合的 6 元和 7 元杂环化合物,如喹啉、异喹啉和苯扎庚素,被用作药物的特殊支架,但对中型(8-11 元)同系物的探索较少。较少探索的独特杂环骨架的设计和合成将有助于扩大化学空间。之前,我们报道了多米诺 (2+2) 环加成——无环醛亚胺与 ynamides 的 4 电环开环反应,通过氮杂环丁烷中间体生成 -不饱和脒(方案 1)。我们明确表示,该反应是由强布朗斯台德酸(如三氟甲磺酸酰亚胺 (Tf2NH) 和磺酸)和 H+ (cat) + R3 N R4 N EWG R1 R2 N R4 N R3 R2 EWG
Alkynes to (E)-enolates using tandem catalysis: stereoselective anti-aldol and syn-[3,3]-rearrangement reactions
作者:Neil P. Grimster、Donna A.A. Wilton、Louis K.M. Chan、Christopher R.A. Godfrey、Clive Green、Dafydd R. Owen、Matthew J. Gaunt
DOI:10.1016/j.tet.2010.05.045
日期:2010.8
A new tandem catalysis strategy that transforms alkyne derivatives to (E)-enol-equivalents followed by stereoselective anti-selective aldol coupling or syn-selective [3,3]-rearrangement transformations is reported. The mechanism is thought to proceed through an interchanging series of Lewis acid and Bronsted acid catalyzed reactions via the intermediacy of a ketiminum ion species. (C) 2010 Elsevier Ltd. All rights reserved.
Selective Synthesis of Polysubstituted Dihydroquinolines and α,β-Unsaturated Amidines by a Catalytic Reaction of Ynamides with Ketimines
amidines. Ynamides reacted with benzophenoneimines in the presence of triflic imide as a catalyst. Ynamides bearing a sulfonamide moiety gave the corresponding 2-amino-3,4-dihydroquinolines selectively in good to high yields. In contrast, yne-carbamates gave the corresponding α,β-unsaturated amidines exclusively. These methods permit simple preparation of stericallycrowded polysubstituted quinolines and