Copper-Catalyzed Intermolecular [2 + 2 + 2] Annulation of Diynes with Alkynes: Construction of Carbazoles
Zhen-Tao Zhang1,2, Chen Luo1,2, Zu-Xin Yu1,2
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:
Transition-metal-catalyzed [2 + 2 + 2] annulation of alkynes is an efficient pathway for the synthesis of aromatic compounds. However, most of the established methods require noble metal catalysts. Herein, we report a copper-catalyzed intermolecular [2 + 2 + 2] annulation of diynes with alkynes through vinyl cation intermediates, enabling the atom-economical preparation of biologically important carbazole skeletons. The reaction shows good regioselectivity in the reaction of aryl(alkyl)alkynes. Moreover, preliminary results have also been obtained for the related catalytic atroposelective transformation. This reaction represents a rare example of non-noble-metal-catalyzed intermolecular [2 + 2 + 2] annulation of ynamides through the vinyl cation pathway.
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