Sen' Vasily D, Golubev Valery A, Shilov Gennadii V, Chernyak Alexander V, Kurmaz Vladimir A, Luzhkov Victor B
Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka 142432, Russian Federation.
Department of Fundamental Physico-Chemical Engineering, Lomonosov Moscow State University, Moscow 119991, Russia Federation.
J Org Chem. 2021 Feb 19;86(4):3176-3185. doi: 10.1021/acs.joc.0c02526. Epub 2021 Jan 15.
Cyclic oxoammonium salts and DMSO are known as important reagents for their diverse and unique reactivity. In the present work, we have studied the reaction of six- and five-membered oxoammonium salts with DMSO. The reaction includes ∼100% selective transfer of the O atom from the >N═O group to the S atom of DMSO and structural rearrangement of the remaining cationic framework, leading to the formation of hydrolytically unstable iminium salts. The logarithms of the bimolecular rate constants of the reaction correlated linearly with the reduction potentials , a relationship known for other electrophile-nucleophile combinations. The kinetic data and results of the DFT calculations allow for the suggestion that the studied process proceeds via the prereactive charge-transfer complex >N═O···S (O)Me and its direct concerted rearrangement to the iminium salts. An alternative mechanism that includes intermediate steps with discrete nitrenium cations can be ruled out on the basis of product analysis and DFT computations. The obtained results allow a deeper understanding of the redox chemistry of a pair of nitroxide radicals-oxoammonium cations.
环状氧鎓盐和二甲基亚砜（DMSO）因其多样且独特的反应活性而被视为重要试剂。在本工作中，我们研究了六元环和五元环氧鎓盐与DMSO的反应。该反应包括氧原子从＞N═O基团近乎100%选择性地转移至DMSO的硫原子上，以及剩余阳离子骨架的结构重排，从而导致形成水解不稳定的亚胺鎓盐。该反应的双分子速率常数的对数与还原电位呈线性相关，这种关系在其他亲电试剂 - 亲核试剂组合中也为人所知。动力学数据和密度泛函理论（DFT）计算结果表明，所研究的过程是通过预反应电荷转移络合物＞N═O···S(O)Me及其直接协同重排为亚胺鎓盐进行的。基于产物分析和DFT计算，可以排除包括离散氮鎓阳离子中间步骤的另一种机制。所获得的结果有助于更深入地理解一对氮氧自由基 - 氧鎓阳离子的氧化还原化学。
