Thermal Ring Contraction Reactions of 9-Aryl-5<i>H</i>,7<i>H</i>-[1,2,5]thiadiazolo[3,4-<i>h</i>][2,3,4]benzothiadiazepine 6,6-Dioxides. Experimental and Computational Studies for Understanding the Course of the Transformations
作者:Ferenc Bertha、Tamás Kégl、József Fetter、Balázs Molnár、András Dancsó、Gábor Németh、Gyula Simig、Balázs Volk
DOI:10.1021/acs.joc.6b02463
日期:2017.2.17
7-chloro-substituted 2,3,4-benzothiadiazepine 2,2-dioxide, the formation of sulfone via o-quinodimethane is the preferred pathway from the zwitterion. However, in the case of thiadiazolobenzothiadiazepine 6,6-dioxides it has been found that the ring closure of the zwitterion leading to the formation of sultines was kinetically preferred over the loss of sulfur dioxide leading to o-quinodimethane, which is the key intermediate
与碳酸氢钠在乙腈中回流时,在失去二氮并随后发生环收缩后,得到7-氯-5-(4-氟苯基)-1,3-二氢-2,3,4-苯并噻二氮杂2,2-二氧化物相应的砜产率为83%。相关噻二唑稠合的三轮车的类似处理,即9-芳基-5 H,7 H- [1,2,5]噻二唑[3,4- h] [2,3,4]苯并噻二氮杂卓6,6-二氧化物导致基本不同的产物混合物:观察到形成了磺胺和苯并环丁烯,而仅形成了少量的砜(如果有的话)。密度泛函理论计算支持所提出的涉及两性离子中间体转化的机理,该两性离子中间体是由噻二氮杂环的互变异构化然后进行二氮挤出而形成的。当从7-氯取代的2,3,4-苯并噻二氮杂2,2-二氧化物开始时,通过o形成砜从两性离子开始,优选的是-喹啉二甲烷。然而,对于6,6-二氮杂噻唑并苯并噻二氮杂,发现在两性离子的闭环反应中会导致形成苏丹嘌呤,这在动力学上比二氧化硫的损失会导致邻喹啉甲烷的损失更为可取。苯并环丁烯