The Thermal Sulfenate−Sulfoxide Rearrangement: A Radical Pair Mechanism
The Thermal Sulfenate−Sulfoxide Rearrangement: A Radical Pair Mechanism
复制标题
热亚硫酸盐-亚砜重排：自由基对机制
DOI：
--
复制
发表时间：
2000
期刊：
影响因子：
--
通讯作者：
O. Wiest
中科院分区：
文献类型：
--
作者：
Jérôme Amaudrut and;O. Wiest
通过实验研究了次磺酸盐 (RS−OR) 的热反应，生成相应的亚砜 (RS(O)R)。发现该反应的第一步是通过次磺酸盐的碳-氧键的均裂断裂形成自由基对。形成的两个瞬时自由基然后重新结合形成亚砜的碳硫键。 4-硝基苯磺酸肉桂酯的热解具有正的活化熵（在甲苯中ΔS⧧ = 6.4 ± 2.0 eu），这是解离途径的特征。还用该底物测量了正常的二次动力学同位素效应（kH/kD = 1.19 ± 0.04）。最后，捕获实验能够分离和表征来自肉桂基自由基和 TEMPO 偶联的产物。这些研究证实了之前基于计算研究提出的机制。实验测定的碳-氧键的键解离能为~28 kcal·mol-1，与计算值~26 k非常吻合。
The thermal reaction of sulfenates (RS−OR), yielding their corresponding sulfoxides (RS(O)R), was studied experimentally. The first step of the reaction was found to be the formation a radical pair by homolytic cleavage of the carbon−oxygen bond of the sulfenate. The two transient radicals formed then recombine to form the carbon−sulfur bond of the sulfoxide. The thermolysis of cinnamyl-4-nitrobenzenesulfenate has a positive entropy of activation (ΔS⧧ = 6.4 ± 2.0 eu in toluene), characteristic of a dissociative pathway. A normal secondary kinetic isotope effect (kH/kD = 1.19 ± 0.04) was also measured with this substrate. Finally, a trapping experiment allowed the isolation and characterization of a product coming from the coupling of the cinnamyl radical and TEMPO. These studies confirm a mechanism that was proposed earlier based on computational studies. The experimentally determined bond dissociation energy of the carbon−oxygen bond of ∼28 kcal·mol-1 is in good agreement with the computed value of ∼26 k...