The cyclopropylcarbinyl route to γ-silyl carbocations
作者:Xavier Creary
DOI:10.3762/bjoc.15.170
日期:——
mesylates and triflates with substituents on the 1-position. These substrates all solvolyze in CD3CO2D to give products derived from cyclopropylcarbinylcations that undergo further rearrangement to give 3-trimethylsilylcyclobutyl cations. These 3-trimethylsilylcyclobutyl cations are stabilized by a long-range rear lobe interaction with the γ-trimethylsilyl group. When the substituent is electron-withdrawing
已经制备了顺-1-羟甲基-2-三甲基甲硅烷基环丙烷的甲磺酸酯衍生物,以及许多相关的甲磺酸酯和在1-位带有取代基的三氟甲磺酸酯。这些底物全部在CD 3 CO 2 D中溶剂溶解,得到衍生自环丙基羰基阳离子的产物,该产物经过进一步重排得到3-三甲基甲硅烷基环丁基阳离子。这些3-三甲基甲硅烷基环丁基阳离子通过与γ-三甲基甲硅烷基的长距离后叶相互作用而稳定化。当取代基是吸电子的(CF 3,CN或CO 2 CH 3),形成大量的双环丁烷产物。双环丁烷是从阳离子中间体中消除了γ-三甲基甲硅烷基的结果,该中间体具有异常长的Si-C键。反式-1-羟甲基-2-三甲基甲硅烷基环丙烷的甲磺酸酯和三氟甲磺酸酯衍生物和1-取代的类似物的溶剂化化学性质可能完全不同,因为这些底物通常不会导致3-三甲基甲硅烷基环丁基阳离子。
The regiochemical course of [2+2] cycloadditions of dichloroketene with vinyl- and alkynylsilanes
作者:Rick L. Danheiser、Howard Sard
DOI:10.1016/s0040-4039(00)81316-7
日期:1983.1
Alkynylsilanes undergo regioselective [2+2] cycloadditions with dichloroketene in good yield; the regiochemical course of these reactions is in accord with frontier molecular orbital predictions.
3-trimethylsilyl-1-arylcyclobutyl carbocations, 10 and 11, where the cross-ring 3-trimethylsilyl group has the potential to interact with the cationic center, have been generated under solvolytic conditions. When the cationic center can interact with the rear lobe of the carbon–silicon bond, rate enhancements become progressively larger as the substituent on the aryl group becomes more electron-withdrawing
Phenyl(trimethylsilyl)ketene. Some ketene reactions with diazomethane
作者:William T Brady、Theresa C Cheng
DOI:10.1016/s0022-328x(00)81435-7
日期:1977.9
Phenyl(trimethylsilyl)ketene was prepared by the zinc dehalogenation of phenyl(trimethylsilyl)bromoacetyl chloride. This ketene parallels tirmethylsilylketene in stabibility and lack of reactivity in cycloaddition reactions. The reaction of phenyl(ethyl)-, phenyl(trimethylsilyl)- and trimethylsilylketenes with diazomethane at −78°C is described. Only the 21 cycloadducts, the cyclobutanones, could be
A series of 3-trimethylsilyl-1-substituted cyclobutyl trifluoroacetates have been prepared and reacted in CD3CO2D. Rate data indicate that the substrates with the trimethylsilyl group cis to the leaving group react with assistance due to γ-silyl participation. Rate enhancements range from a factor of 209 for α-phenyl-substituted cations to 4.6 × 104 for α-methyl-substituted cations to >1010 for the