已经合成了具有和不具有侧翼甲基的一系列对-环丙基苯基tropyliumium离子以及作为参考化合物的各种甲基取代的苯基tropyliumium离子。通过1 H nmr光谱,p K R +测量以及铬(II)离子对单电子还原的速率测量,研究了对环丙基对阳离子稳定性的构象效应。检查1 H nmr光谱和这些阳离子的p K R +值表明,由于电荷离域到对位体而产生的稳定作用-环丙基随着侧翼甲基的引入而减少。当绘制铬(II)离子还原的log k 2与未取代的m-和p-甲基-,m,m-二甲基-和m-和p-甲基-的取代基常数σ +的总和时,观察到线性自由能关系。p -环丙基- phenyltropylium离子,但登录ķ 2为p具有一个或两个侧翼甲基的β-环丙基取代的阳离子大大偏离线性相关线,反映出由于环丙基的构象变化而导致的稳定性损失。
Silylium-Ion-Promoted Ring-Opening Hydrosilylation and Disilylation of Unactivated Cyclopropanes
作者:Avijit Roy、Vittorio Bonetti、Guoqiang Wang、Qian Wu、Hendrik F. T. Klare、Martin Oestreich
DOI:10.1021/acs.orglett.0c00173
日期:2020.2.7
hydrosilylation of unactivated cyclopropanes is reported. The reaction is facilitated by the γ-silicon effect, and the regioselectivity is influenced by various stabilizing effects on the carbenium-ion intermediates, including the β-silicon effect. The experimental observations are in accord with the computed reaction mechanism. The work also showcases the ability of silylium ions to isomerize cyclopropyl to allyl
Lewis Base-Promoted Ring-Opening 1,3-Dioxygenation of Unactivated Cyclopropanes Using a Hypervalent Iodine Reagent
作者:Matthew H. Gieuw、Zhihai Ke、Ying-Yeung Yeung
DOI:10.1002/anie.201713422
日期:2018.3.26
A facile and effective system has been developed for the regio‐ and chemoselective ring‐opening/electrophilic functionalization of cyclopropanes through C−C bond activation by [bis(trifluoroacetoxy)iodo]benzene with the aid of the Lewis basic promoter p‐toluenesulfonamide. The p‐toluenesulfonamide‐promoted system works well for a wide range of cyclopropanes, resulting in the formation of 1,3‐diol products
Aminofluorination of Cyclopropanes: A Multifold Approach through a Common, Catalytically Generated Intermediate
作者:Cody Ross Pitts、Bill Ling、Joshua A. Snyder、Arthur E. Bragg、Thomas Lectka
DOI:10.1021/jacs.6b02838
日期:2016.5.25
We have discovered a highly regioselective aminofluorination of cyclopropanes. Remarkably, four unique sets of conditions-two photochemical, two purely chemical-generated the same aminofluorinated adducts in good to excellent yields. The multiple, diverse ways in which the reaction could be initiated provided valuable clues that led to the proposal of a "unifying" chain propagation mechanism beyond
A copper-catalyzed 1,3-aminothiocyanation of arylcyclopropanes with N-fluorobenzenesulfonimide (NFSI) and trimethylsilyl isothiocyanate (TMSNCS) has been developed for the first time, efficiently synthesizing a series of γ-aminothiocyanate derivatives in moderate to excellent yields from readily available substrates under mild conditions. The practicability of the reaction was demonstrated by gram-scale
Copper-Catalyzed Ring-Opening 1,3-Aminotrifluoromethylation of Arylcyclopropanes
作者:Huan Zhang、Haiwen Xiao、Feng Jiang、Yewen Fang、Lin Zhu、Chaozhong Li
DOI:10.1021/acs.orglett.1c00390
日期:2021.3.19
(bpy)Zn(CF3)2 (bpy = 2,2′-bipyridine) at room temperature affords the corresponding ring-opening 1,3-aminotrifluoromethylation products in satisfactory yields. The protocol is highly regioselective, providing a convenient entry to γ-trifluoromethylated amines. A mechanism involving the trifluoromethylation of benzyl radicals is proposed.