据报道,强硼路易斯酸B(C 6 F 5)3催化乙烯基环丙烷(VCP)的硅氢化。对于大多数VCP,观察到很少或没有环丙基单元的开环。相反,对于具有庞大R基团的VCP,例如邻位取代的芳基环或支链烷基残基,开环是唯一的反应途径。这一发现可以通过阻止氢化物向空间屏蔽的,β-硅稳定的环丙基羰基阳离子中间物的传递来解释。
Silylium‐Ion‐Promoted (5+1) Cycloaddition of Aryl‐Substituted Vinylcyclopropanes and Hydrosilanes Involving Aryl Migration
作者:Tao He、Guoqiang Wang、Vittorio Bonetti、Hendrik F. T. Klare、Martin Oestreich
DOI:10.1002/anie.202004320
日期:2020.7.13
A transition‐metal‐free (5+1) cycloaddition of aryl‐substituted vinylcyclopropanes (VCPs) and hydrosilanes to afford silacyclohexanes is reported. Catalytic amounts of the trityl cation initiate the reaction by hydride abstraction from the hydrosilane, and further progress of the reaction is maintained by self‐regeneration of the silylium ions. The new reaction involves a [1,2] migration of an aryl
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
A molybdenum-mediated reductive hydroamination of vinylcyclopropanes with nitroarenes has been developed. A broad range of substituted homoallylamines were prepared in good to excellent yields from readily available starting materials. No noble metal catalysts were used in this reaction, and Mo(CO)6 acted as both catalyst and reductant. This protocol provides an effective method for the selective synthesis
Rh(II)-Catalyzed Ring Expansion of Cyclopropyl N-Tosylhydrazones to 1-Substituted Cyclobutenes
作者:Jingfeng Huo、Jianbo Wang、Wenbai Ouyang
DOI:10.1055/a-1995-5960
日期:——
useful synthetic intermediates as well as important motifs in functional molecules. Herein, we report a straightforward access toward monosubstituted cyclobutenes from cyclopropyl N-tosylhydrazone. 1,2-Aryl or -alkyl shift of the Rh(II) carbene intermediate plays the key role in this transformation.
Aryl boronic acid-controlled divergent ring-contraction and ring-opening/isomerization reaction of <i>tert</i>-cyclobutanols enabled by nickel catalysis
In this work, we wish to present a nickel-catalyzed divergent ring-contraction and ring-opening/isomerization reaction of tert-cyclobutanols. The key to control these two different reaction pathways is to choose appropriate boronic acid, where the use of phenylboronic acid and pyrimidin-5-ylboronic acid enables a ring-contraction and ring-opening reaction/isomerization, respectively. Both cyclopropyl