A New Route to Ring-Fused Pyrazines: Imidazo[4,5-b]Quinoxalines by a Simple Oxidation-Annulation Sequence
作者:Rainer Beckert、Ernst-Ulrich Würthwein、Svenja Herzog、Gunther Buehrdel、Susann Klimas、Stefan Grimme、Helmar Görls
DOI:10.1055/s-0029-1217071
日期:2009.12
Novel tricyclic 4H-imidazo[4,5-b]quinoxalines were synthesized by a new ortho-annulation process starting from 4H-imidazoles and cerammonium nitrate (CAN) as oxidation reagent in the presence of potassium carbonate as base. This reaction is interpreted as a multi-step reaction involving oxidative radical formation, a radical aromatic substitution and a subsequent redox process. The analysis is supported
在碳酸钾为碱的存在下,以4 H-咪唑和硝酸铈铵(CAN)为氧化剂,通过新的邻位环化工艺合成了新型三环4 H-咪唑并[4,5- b ]喹喔啉。该反应被解释为涉及氧化自由基形成,自由基芳族取代和随后的氧化还原过程的多步骤反应。高级DFT计算支持该分析。这种新颖的转化为吡嗪的环稠合衍生物的构建开辟了道路。新的三环产品在溶液中显示出强荧光,此外还显示出可逆的氧化还原活性。 胺-杂环-氧化-自由基反应-闭环