PtCl<sub>2</sub>-Catalyzed Rearrangement of Methylenecyclopropanes
作者:Alois Fürstner、Christophe Aïssa
DOI:10.1021/ja061392y
日期:2006.5.1
Alkylidenecyclopropanes readily convert into cyclobutene derivatives on treatment with catalytic amounts of PtCl2. The reaction is strongly accelerated when performed under an atmosphere of CO (1 atm). The resulting cyclobutenes are isolated in good to excellent yields for substrates bearing aliphatic as well as aromatic substituents R on their olefinic site. If the substituent R, however, is a very
亚烷基环丙烷在用催化量的 PtCl2 处理后很容易转化为环丁烯衍生物。当在 CO (1 atm) 气氛下进行时,反应会大大加速。对于在其烯属位点上带有脂肪族和芳香族取代基 R 的底物,所得环丁烯的分离产率良好至极好。但是,如果取代基 R 是非常富电子的芳烃,则最初形成的环丁烯会进一步反应生成二聚产物,其中含有以前未知的 1,2,2a,7a-四氢螺[环丁[a]茚-7,1'-环丁烷骨架。提出了解释这些实验观察以及氘标记实验的机制,这意味着非经典阳离子/卡宾界面处的反应性中间体。此外,还表明 PtCl2 催化的环丁烯形成可以与随后的开环/闭环复分解 (ROM/RCM) 事件相适应。最后,提出了一种方便的“一锅”方法,用于制备本研究中使用的亚烷基环丙烷底物,该方法基于改进的 Julia-Kocienski 醛烯化与现成的 1-叔丁基-1H-四唑-5- Barbier条件下的基-环丙基砜。
Oxidative Ring Contraction of Cyclobutenes: General Approach to Cyclopropylketones including Mechanistic Insights
作者:Andreas N. Baumann、Franziska Schüppel、Michael Eisold、Andrea Kreppel、Regina de Vivie-Riedle、Dorian Didier
DOI:10.1021/acs.joc.8b00297
日期:2018.5.4
cyclopropylketones (CPKs) under atmospheric conditions is reported. Comprehensive mechanistic studies are proposed to support this novel, yet unusual, rearrangement. Insights into the mechanism ultimately led to simplification and generalization of the ring contraction of cyclobutenes using mCPBA as an oxidant. This unique and functional group tolerant transformation proceeds under mild conditions at room temperature
A regioselective Markovnikov hydroarylation of arylcyclobutene has been developed using Brønsted acid catalysis through a protonation/Friedel‐Crafts sequence. The metal‐free catalytic reaction is operationally simple and feasible compared to previous reports that utilized elaborate arylcyclobutene and specific polyfluorinated reagents, affording a variety of gem‐diaryl‐ substituted arylcyclobutene
N‐(sulfonio)sulfilimine reagents: Non‐oxidizing Sources of Electrophilic Nitrogen Atom for Skeletal Editing
作者:Tobias Heilmann、Juan M Lopez-Soria、Johannes Ulbrich、Johannes Kircher、Zhen Li、Brigitte Worbs、Christopher Golz、Ricardo A Mata、Manuel Alcarazo
DOI:10.1002/anie.202403826
日期:——
Under rhodium catalysis N-sulfonio(sulfilimines) act as sulfonitrene precursors. Reaction of such species with indenes presumably delivers N-sulfonio aziridines, which evolve to isoquinolines via electrocyclic ring expansion. Contrarily, 1-arycyclobutenes are transformed into 1-cyano-1-arylcyclopropanes via ringcontraction.
Laser Flash Photolysis Study of Arylcyclopropylcarbenium Ions: Cation Stabilizing Abilities of Cyclopropyl and Phenyl Groups
作者:Wolfgang Kirmse、Birgit Krzossa、Steen Steenken
DOI:10.1021/ja960268j
日期:1996.1.1
Arylcyclopropylcarbenium ions, Ar(c-Pr)CH+, were generated as transient intermediates by laserflashphotolysis (LFP) of trans-2,3-diphenylaziridinimines of aryl cyclopropyl ketones in 2,2,2-trifluoroethanol (TFE). The carbocations are thought to arise by way of diazo compounds and carbenes. Rate constants for the unimolecular decay in TFE and for the bimolecular reaction with methanol in TFE were