Copper‐Catalyzed C(sp3)− Functionalization and Annulation of 2‐Bromoaryl Oximes with Active Methylene Compounds towards Synthesis of Isoquinoline N‐Oxides

The established process proceeds through copper (II)‐catalyzed C(sp3)− functionalization of β‐diketones/β‐ketoesters with 2‐bromobenzaldehyde oximes followed by the intramolecular cyclization of in situ generated acylated intermediates to deliver isoquinoline N‐oxides. The copper(II) acetate catalyzed C−H functionalization showed maximum efficacy at 60 °C in methanol/toluene as solvent. The described reaction conditions were applicable over a wide range of substrates with a variety of functional groups to yield isoquinoline N‐oxides in yields up to 85%. The developed approach was further elucidated by means of control experiments and DFT calculations.