Phosphoric Acid-Catalyzed Alkene Difunctionalization of 2-Vinylpyridines via HOMO/LUMO Biactivated Diels-Alder
Shu-Shu Xiong1, Cui Jian1, Yan-Qing Mo2
1College of Science, Shenyang University of Chemical Technology, Shenyang 110142, China.
Abstract:
The difunctionalization of vinylpyridines based on the cyclization strategy remains rare and underdeveloped, in contrast to the well-developed hydrogen functionalization. Current exploration on [4 + 2] cyclization of vinylpyridines mainly relies on extremely high temperatures and the LUMO activation of vinylpyridines using boron trifluoride as a strong Lewis acid. Herein, we established a phosphoric acid-catalyzed [4 + 2] cyclization reaction of 3-vinyl-1H-indoles and 2-vinylpyridines by means of the LUMO/HOMO bifunctional activation model. This protocol features mild reaction conditions, high functional group tolerance, broad substrate compatibility, and high diastereoselectivity, enabling the efficient construction of various functionalized pyridine-substituted tetrahydrocarbazoles with prominent potential in drug discovery.
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