Palladium‐Catalyzed 8‐Aminoquinoline‐Aided sp2δ‐C−H Intramolecular Amidation/Annulation: A Route to Tricyclic Quinolones

Abstract

Systematic investigations of a Pd(II)‐catalyzed, 8‐aminoquinoline directing group (DG)‐aided sp2 δ‐C−H amidation (C−N bond formation) of different biaryl carboxamides are reported. Various biaryl carboxamides with suitably positioned sp2 δ‐C−H bond with respect to the DG were assembled via β‐C−H arylation and then they were subjected to Pd(II)‐catalyzed sp2 δ‐C−H intramolecular amidation/annulation reactions. While the intramolecular amidation of the sp2 δ‐C−H bond of some carboxamides was not fruitful, several biaryl carboxamides underwent intramolecular amidation of their sp2 δ‐C−H bonds to afford various tricyclic quinolone motifs such as, phenanthridin‐6(5H)‐ones and thieno‐/furo‐/pyrrolo‐[2,3‐c]quinolin‐4(5H)‐ones. The assembly of the required biaryl carboxamides possessing the sp2 δ‐C−H bond via the β‐C−H arylation and the successive intramolecular amidation (C−N bond formation) of the resulting biaryl carboxamides were also performed in one‐pot reaction conditions to afford tricyclic quinolones.