Synthesis of 1,1-Dialkylindolium-2-thiolates via Base-Induced Transformation of 4-(2-Chloro-5-nitrophenyl)-1,2,3-thiadiazole in the Presence of Secondary Amines
摘要:
4-(2-Chloro-5-nitrophenyl)-1,2,3-thiadiazole undergoes ring-opening to produce a thioketene intermediate that reacts with secondary amines forming 2-(2-chloro-5-nitrophenyl)-N,N-dialkylthioacetamides. Intramolecular cyclization of these thioamides via nucleophilic substitution of the halogen on the aromatic ring affords nonaromatic 1,1-dialkylindolium-2-thiolates instead of the expected aromatic N,N-dialkylaminobenzo[b]thiophenes.
4-(2-氯-5-硝基苯基)-1,2,3-噻二唑进行开环反应生成硫代烯酮中间体,该中间体与O-或N-亲核试剂反应,形成芳基取代的硫代乙酸的酯或酰胺酸。通过芳香环中卤素的亲核取代,硫代乙酸衍生物的分子间环化反应会得到N-取代的吲哚-2-硫醇(如果是N-亲核试剂)或2-烷氧基取代的苯并[ b ]噻吩(如果是的亲核试剂)。该反应也适用于N-取代的吲哚-2-硫醇的杂环类似物的合成:1-丁基-1,3-二氢吡咯并[2,3- b以[吡啶] -2-硫酮为例进行了合成。在硫代乙酸钾(S-亲核试剂)的存在下,4-硝基-2-(1,2,3-噻二唑-4-基)苯硫醇的生成速度比噻二唑开环更快,从而使杂环对碱基的耐受性。