Synthesis of Oxaspirocyclohexadienones via Lewis‐acid Catalyzed [2+3]‐Annulations of p‐Quinone Methides and Iodonium Ylides

Herein, we report a mild method for the synthesis of oxaspirocyclohexadienones by using a combination of Lewis acid‐HFIP mediated [2+3]‐annulation of p ‐quinone methides ( p‐ QMs) and iodonium ylides. The proposed mechanism proceeds through a one‐pot sequence of carbonyl activation/cyclopropyl formation/Cloke‐Wilson rearrangement to provide a broad range of oxaspirocyclohexadienones in moderate to high yields. Interestingly, the spiro‐annulated products were further converted to tetrahydroxanthane derivatives via BF 3 .OEt 2 mediated dienone‐phenol rearrangement pathway. Moreover, the spiro‐annulated derivatives also showed a moderate anti‐tuberculosis activity against Mycobacterium tuberculosis H37Ra ATCC25177.