Easy access to 4-nitrothiochroman S,S-dioxides via ring-enlargement from 3-nitrobenzo[b]thiophene
作者:Lara Bianchi、Carlo Dell'Erba、Massimo Maccagno、Stefano Morganti、Marino Novi、Giovanni Petrillo、Egon Rizzato、Fernando Sancassan、Elda Severi、Domenico Spinelli、Cinzia Tavani
DOI:10.1016/j.tet.2004.04.039
日期:2004.5
easily be oxidized to the relevant sulfones 6 and effectively subjected to cyclization via an intramolecular Michael addition after metallation with lithium bis(trimethylsilyl)amide in THF. After quenching with ammonium chloride the 3-aryl-4-nitrothiochroman S,S-dioxides 2 are obtained as diastereomeric mixtures in good to excellent yields. Both yields and stereochemistry of the ring-closure step appear
(E)-2-芳基-1- [2-(甲硫基)苯基] -1-硝基乙烯5可以很容易地氧化成相关的砜6并在用双(三甲基甲硅烷基)锂金属化后通过分子内迈克尔加成反应有效地进行环化酰胺在THF中的溶液。用氯化铵淬灭后,以非对映异构体混合物的形式获得3-芳基-4-硝基硫代苯并二氢吡喃S 2,S-二氧化物2,收率良好至优异。闭环步骤的产率和立体化学似乎都受到3-芳基部分的空间效应的影响。由于硫化物5源自3-硝基苯并[ b ]噻吩(1),整个1到2的过程可以被认为是硫杂环的5到6个环的有效扩环。还完成了对分离的非对映异构体2的构象1 H NMR和分子力学研究。