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。
A relay catalytic cascade process involving Lewis acid triggered ring-opening of cyclopropyl ketones with nitriles, the copper(I)-catalyzed Ritter process, and acid-promoted N-acyliminium ion cyclization is described, which efficiently provides thieno-, furano-, and benzo-indolizinones in moderate to good yields.
An iodine‐mediated oxidative ring contraction of cyclobutanols has been developed. The reaction allows the synthesis of a wide range of aryl cyclopropyl ketones under mild and eco‐friendly conditions. A variety of functional groups including aromatic or alkyl halides, ethers, esters, ketones, alkenes, and even aldehydes are nicely tolerated in the reaction. This is in contrast with traditional synthetic
efficient AuIII‐catalyzed method to generate the highly reactive cyclic o‐quinodimethane (o‐QDM) species from easily available enynals or enynones is presented (see scheme). This method produced a variety of structurally unique fan‐like products with the advantages of mild reaction conditions, excellent diastereoselectivities, and high functional‐group tolerance.
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
β-unsaturated ketones could be obtained by palladium-catalyzed ring-opening of mono-substituted cyclopropyl ketones efficiently and systematically. (E)-1-Arylbut-2-en-1-ones were generated from aryl cyclopropyl ketones stereoselectively in yields of 23–89% by the Pd(OAc)2/PCy3 catalytic system. The reaction exhibited stereoselectivity (only E products were found) and was suitable for both phenyl and
在此,我们报道通过钯催化的单取代环丙基酮的开环可以有效且系统地获得α,β-不饱和酮。( E )-1-Arylbut-2-en-1-ones 通过 Pd(OAc) 2 /PCy 3催化体系由芳基环丙基酮立体选择性生成,收率为 23-89% 。该反应表现出立体选择性(仅发现E产物)并且适用于苯基和杂芳基环丙基酮。