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

An efficient insitu 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.