Copper-Catalyzed Formal [4 + 1] Annulation toward Diverse Trifunctionalized Indolizines from Pyridinium 1,4-Zwitterionic Thiolates and Diazos
Wen Li, Hexiang Wang, Yuan Zhang, Limin Zhao, Pengfeng Guo, Hua Cao, Xiang Liu
Abstract
Pyridinium 1,4-zwitterionic thiolates were regarded as powerful and versatile building blocks to prepare nitrogen- and sulfur-containing heterocycles. Herein, we reported a copper-catalyzed formal [4 + 1] annulation of pyridinium 1,4-zwitterionic thiolates and diazo compounds without any additives to access a library of trifunctionalized indolizines in good yields. Besides, isoquinolinium 1,4-zwitterionic thiolates and imidazolium 1,4-zwitterionic thiolates were also applied to this formal [4 + 1] annulation reaction. Of particular note is that various functional groups such as −CO 2 R, −CO 2 NR 2, −CF 3, −CN, and −(O)P(OR) 2 could be easily introduced into cycloaddition products indolizines by this strategy.