A Metal-Free Domino Process for Regioselective Synthesis of 1,2,4-Trisubstituted Pyrroles: Application toward the Formal Synthesis of Ningalin B
作者:Virendra Kumar、Annapurna Awasthi、Abhisek Metya、Tabrez Khan
DOI:10.1021/acs.joc.9b01520
日期:2019.9.20
acid/base-free domino process is developed for the regioselective synthesis of 1,2,4-trisubstituted pyrroles. The process involves 1,3-dipolar cycloaddition of unsymmetrical azomethine ylide resulting from the thermal C–C bond cleavage of unactivated aziridines with β-bromo-β-nitrostyrene, followed by a cascade of elimination and aromatization reaction sequence to preferentially furnish 1,2,4-trisubstituted
开发了一种新的单锅,过渡金属,无酸/无碱的多米诺骨牌工艺,用于区域选择性合成1,2,4-三取代的吡咯。该过程涉及不对称的偶氮甲内酯的1,3-偶极环加成反应,这是由于未活化的氮丙啶与β-溴-β-硝基苯乙烯的热C–C键裂解所致,随后是一系列消除和芳构化反应序列,优先提供1,2 1,4-三取代的吡咯代替预期的1,2,3-三取代的吡咯,收率良好至极佳。此外,描述了该方法用于形式的宁格林B的合成。