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Copper-Catalyzed Formal [4 + 1] Annulation of Diynes with Isoxazoles: Synthesis of Pyrrolo[3,4-b]indoles
Tian-Qi Hu1, Ya-Nan Meng1, Yi-Jie Zheng1
1Key Laboratory of Chemical Biology of Fujian Province and State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
Abstract:
Catalytic annulation of isoxazoles with alkynes is an efficient methodology for the assembly of N-heterocyclic architectures, and most reactions require noble-metal catalysts. Herein, we disclose a copper-catalyzed formal [4 + 1] annulation of 1,6-diynes with isoxazoles for the efficient and atom-economical construction of biologically important pyrrolo[3,4-b]indoles in high yields via vinyl cation intermediates, which is significantly different from previous annulations of alkynes with isoxazoles involving α-imino metal carbene intermediates. Interestingly, preliminary results have been obtained for the related catalytic atroposelective transformation. Computational mechanistic studies are employed to elucidate the reaction mechanism.
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