TBAI-Catalysed Formal [4+4]-Cycloaddition: Easy Access to Oxa-Bridged Eight-Membered Heterocycles
Wenxiang Wang1, Chao Pi1, Xiuling Cui1
1Henan Key Laboratory of Chemical Biology and Organic Chemistry, Key Laboratory of Applied Chemistry of Henan Universities, Green Catalysis Center and College of Chemistry, Zhengzhou University, Zhengzhou, 450052, P. R. China.
Abstract:
TBAI-catalysed [4+4]-cyclization reaction of anthranils with hydrazones to deliver oxa-bridged eight-membered heterocycles in accepted yields was developed. Preliminary mechanistic studies indicated that the reaction involved the in situ generation of vinyldiazenes from readily available hydrazones followed by an aza-Michael addition of the anthranil substrates onto the vinyldiazenes and subsequent annulation. This transformation involved the formation of two new C-N bonds and C-O bond in one pot, overcoming the synthetic limitations of anthranils in organic chemistry. This strategy benefits from high efficiency and atomic economy with mild reaction conditions.
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