TBAI-Catalysed Formal [4+4]-Cycloaddition: Easy Access to Oxa-Bridged Eight-Membered Heterocycles

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.

Automated summary

A TBAI-catalysed [4+4]-cyclization reaction was developed for the synthesis of oxa-bridged eight-membered heterocycles from anthranils and hydrazones. Mechanistic studies showed the in situ generation of vinyldiazenes from hydrazones, followed by an aza-Michael addition and subsequent annulation. This strategy overcomes the limitations of anthranils in organic chemistry and provides a high efficiency and atom economical approach.