Dose Stevens Rearrangement Really Proceed via a [1,2] Radical Rearrangement?

史蒂文斯重排真的是通过[1,2]激进重排进行吗？

• 批准号: 05671764
• 负责人: SHIRAI Naohiro
• 金额: $ 1.09万
• 依托单位: Nagoya City University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 1994
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05671764/
• 关键词: AMMONIUM YLIDE; DESILYLATION; STEVENS REARRANGEMENT; SOMMELT-HAUSER REARRANGEMENT; SIGMATROPIC REARRANGEMENT; RADICAL REARRANGEMENT; [1,2] REARRANGEMENT; [2,3] REARRANGEMENT; アンモニウム・イリド; Sommelet-Hauser転位; アンモニウムイリド

Stevens rearrangement is a typical reaction of ammonium ylides. The mechanism has been the subject of much study, and a [1,2] radical rearrangement pathway in the solvent cage has been considered. In the papers that reported high yields of Stevens products, most of the migrating groups were benzyl groups.In my previous studies of chemical behavior of N,N-dimethylbenzylammonium alkylides, produced by fluoride ion induced desilylation of N-benzyl-N,N-dimethyl-alpha-(trimethylsilyl) alkylammonium halides, I reported that Stevens products were formed from isotoluenes which were formed by a [2,3] sigmatropic rearrangement of the alkylides (two steps mechanism). There is no [1,2] shift from the alkylides to the Stevens products.In this research project, I investigated the chemical behavior of N-alkyl-N,N-dimethylammonium benzylides. When a migrating group (R) was an alkyl, no rearrangement occurred but moderate yields of Stevens products were obtained when R was CH_2CN.In the two steps mechanism, is chirality of the migrating group retained? Stevens product prepared from optically-active S-(-)-N,N-dimethy-N-(trimethylsilyl) methyl-1-phenethylammonium iodide retained the chirality during a [2,3] rearrangement followed by a [1,3] shift.These results revealed that Stevens rearrangement has two reaction mechanisms.

史蒂文斯重排反应是典型的叶立德铵反应。其机理一直是许多研究的主题，并考虑了溶剂笼中的[1，2]自由基重排途径。在报道Stevens产物高产率的文献中，大多数迁移基团是苄基。在我之前对氟离子诱导N-苄基-N，N-二甲基α-(三甲基硅基)烷基卤化铵脱硅生成的N，N-二甲基苄基烷基烷内酯的化学行为的研究中，我报道了Stevens产物是由烷基化合物[2，3]Sigmatroic重排(两步反应机理)形成的同位甲苯形成的。在本研究项目中，我研究了N-烷基-N，N-二甲基苯甲酸铵的化学行为。当迁移基团(R)是烷基时，没有发生重排，但当R是CH2CN时，Stevens产物的产率适中。在两步反应机制中，迁移基团的手性被保留了吗？由光学活性的S-(-)-N，N-二甲基-N-(三甲基硅基)甲基-1-苯乙基铵制备的Stevens产物在[2，3]重排和[1，3]位移的过程中保持了手性，这些结果表明Stevens重排有两个反应机理。