Tandem aza-Michael/spiro-ring closure sequence: access to a versatile scaffold and total synthesis of (±)-coerulescine
摘要:
The total synthesis of the alkaloid (+/-)-coerulescine is presented. The key step of this approach is an efficient tandem aza-Michael initiated ring closure (aza-MIRC) process between ethoxymethylene-oxindole and benzyl(2-bromoethyl)carbamate. The potency of the aza-MIRC reaction was first tested onto less challenging Michael acceptors and led in good yields to the corresponding N-Cbz alpha-alkoxy-beta-gem-disubstituted pyrrolidines. The resulting N-acyliminium precursor obtained from ethoxymethylidene-oxindole was efficiently converted in four steps, including 2 deprotections, into the targeted (+/-)-coerulescine. (C) 2013 Elsevier Ltd. All rights reserved.
Synergistic Gold(I)/Trimethylsilyl Catalysis: Efficient Alkynylation of N,O-Acetals and Related Pro-Electrophiles
作者:Malina Michalska、Olivier Songis、Catherine Taillier、Sean P. Bew、Vincent Dalla
DOI:10.1002/adsc.201400169
日期:2014.6.16
This unprecedented manifold opens avenues for developing synergistic silyl‐gold(I)‐catalyzed alkynylation strategies of diverse pro‐electrophiles which were heretofore unattainable, the proof of concept being principally exemplified herein with the first catalytic alkynylation of N,O‐acetals. The reaction proceeds at low catalyst loading, employs mild reaction conditions, is easily scalable, and affords
我们报告了一种独特的机理指导的反应,该反应增强和扩展了目前容易产生的乙炔化金(I)的化学空间。我们的策略利用了具有特定抗衡离子(LAuX – X =三氟甲磺酸或三氟甲磺酸的金(I)嗜碳催化剂的倾向。 )有效激活和去甲硅烷基化三甲基甲硅烷基炔烃,从而原位介导形成等量和催化量的可调强度的甲硅烷基路易斯酸(TMSX)和亲核性金(I)乙炔化物。这种空前的流形为开发各种原亲电子的协同甲硅烷基金(I)催化的炔基化策略开辟了道路,这是迄今为止无法实现的,本文主要以N,O-乙缩醛的首次催化炔基化为例来证明概念验证。该反应在低催化剂负载下进行,采用温和的反应条件,易于扩展,并以良好或优异的产率提供炔丙基内酰胺产物。此外,它完全适用于各种结构和功能的底物,并且还可以扩展到除N,O-乙缩醛以外的其他亲电子试剂。已经进行了控制实验,这些实验强烈支持了我们的双重反应机理建议,与TMSNTf 2相比)和所使用的金抗衡
Tandem aza-Michael/spiro-ring closure sequence: access to a versatile scaffold and total synthesis of (±)-coerulescine
作者:Meral Görmen、Ronan Le Goff、Ata Martin Lawson、Adam Daïch、Sébastien Comesse
DOI:10.1016/j.tetlet.2013.02.047
日期:2013.4
The total synthesis of the alkaloid (+/-)-coerulescine is presented. The key step of this approach is an efficient tandem aza-Michael initiated ring closure (aza-MIRC) process between ethoxymethylene-oxindole and benzyl(2-bromoethyl)carbamate. The potency of the aza-MIRC reaction was first tested onto less challenging Michael acceptors and led in good yields to the corresponding N-Cbz alpha-alkoxy-beta-gem-disubstituted pyrrolidines. The resulting N-acyliminium precursor obtained from ethoxymethylidene-oxindole was efficiently converted in four steps, including 2 deprotections, into the targeted (+/-)-coerulescine. (C) 2013 Elsevier Ltd. All rights reserved.
Atom-Economic Catalytic Direct Substitution of N,O-Acetals with Simple Ketones
作者:Bahria Touati、Abderrahman El Bouakher、Mohamed Salah Azizi、Catherine Taillier、Raja Ben Othman、Malika Trabelsi-Ayadi、Sylvain Antoniotti、Elisabet Duñach、Vincent Dalla
DOI:10.1002/ejoc.201700530
日期:2017.8.17
protocol for the direct amidoalkylation of simple enolizable ketones with use of Lewis superacid Sn(NTf2)4 as a catalyst is described. Couplings of a large set of both carbonyl and N,O-acetalic substrates (mostly the simplest OH-hemiaminals) proceed with very low catalyst loadings (≤ 1 mol-%) and provide the corresponding amidoalkylated ketones in high yields (up to 99 %).