NHC as the Guiding Factor in a Copper-Catalyzed Intramolecular C Arylation of Pyrrolylimidazolium Salts: Synthesis of Luminescent Heterotetracyclic Frameworks
作者:Olesya A. Tomashenko、Mikhail S. Novikov、Alexander F. Khlebnikov
DOI:10.1021/acs.joc.6b02627
日期:2017.1.6
-imidazol-3-ium bromides undergo a copper-catalyzed intramolecular direct C arylation under mild conditions to give new heterocyclic frameworks. The cyclizations involve the formation of betaines (imidazoliumylpyrrolides) under basic conditions and the tautomerizaton of the betaines to the corresponding NHCs, which are the reactive species responsible for the selectivity of the arylation via the formation
3-(2 / 4-(2-溴苯基)-1 ħ -吡咯-3-基)-1 ħ咪唑-3-鎓溴化物经历温和的条件下的铜-催化的分子内直接芳基化Ç,得到新的杂环骨架。环化涉及在碱性条件下甜菜碱的形成(咪唑基吡咯烷酮)和甜菜碱与相应的NHC的互变异构,它们是通过形成NHC-Cu络合物而对芳基化反应负责的反应性物种。将伯盐芳基化产物脱卤化氢,得到7 H-咪唑并[2,1- a ]吡咯并[3,2- c ]异喹啉和1 H-咪唑并[2,1- a ]吡咯并[3,4 - ç]异喹啉杂环骨架,通过除去苄基-PG ,它们分别进一步转变成热力学上更稳定的1 H-和6 H-互变异构体。新的杂环系统在具有高量子产率的溶液中具有荧光。