NHC‐Catalyzed Enantioselective [4+3] Cycloaddition of Ortho‐Hydroxyphenyl Substituted Para‐Quinone Methides with Isatin‐Derived Enals

Abstract The first enantioselective cycloaddition of ortho ‐hydroxyphenyl substituted para ‐quinone methides has been established by employing isatin‐derived enals as suitable 3C‐synthons under chiral N ‐heterocyclic carbene catalysis. By using this strategy, biologically important ϵ‐lactones have been prepared in good yields (up to 89%) and excellent asymmetric inductions (up to >99% ee, >20:1 dr). Notably, this methodology opens a direct [4+3] annulation entry for the asymmetric synthesis of spirobenzoxopinones bearing an oxindole moiety connected through the spirocenter. magnified image