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.

史蒂文斯重排是铵叶立德的典型反应。该机制已成为许多研究的主题，并且已经考虑了溶剂笼中的[1,2]自由基重排途径。在报道Stevens产品高产率的论文中，大多数迁移基团都是苄基。在我之前对N,N-二甲基苄基烷基铵化学行为的研究中，N,N-二甲基苄基铵烷基化物是由氟离子诱导N-苄基-N,N-脱甲硅烷基化产生的。二甲基-α-（三甲基硅基）烷基卤化铵，我报道史蒂文斯产品是由异甲苯形成的，异甲苯是由[2,3] sigmatropic烷基化物的重排（两步机制）。不存在从烷基化物到史蒂文斯产物的 [1,2] 转变。在这个研究项目中，我研究了 N-烷基-N,N-二甲基铵苯甲基化物的化学行为。当迁移基团(R)为烷基时，不会发生重排，但当R为CH_2CN时，得到了中等产率的Stevens产物。在两步机理中，迁移基团的手性是否保留？由光学活性 S-(-)-N,N-二甲基-N-(三甲基甲硅烷基)甲基-1-苯乙基碘化铵制备的史蒂文斯产物在 [2,3] 重排和随后的 [1,3] 位移过程中保留了手性这些结果表明史蒂文斯重排有两种反应机制。