NHC‐Catalyzed Efficient Syntheses of Isoquinolinones or Isochromanones through Formal [4+2] Cycloaddition of o ‐Quinodimethanes with Acylhydrazones or Ketones

Abstract An efficient in situ generation of ortho‐quinodimethane ( o ‐QDM) from 2‐methyl‐3,5‐dinitrobenzoic acid through N ‐Heterocyclic Carbene (NHC) catalysis, which underwent a formal [4+2] annulation with activated C=O (or C=N) bonds for the assembly of isoquinolinone and isochromanone scaffolds, was disclosed. This method features challenging direct functionalizations of C(sp3)‐H bond, readily available starting materials, mild reaction conditions and good yields.