Programmed Multiple C‐H Bond Functionalization of the Privileged 4‐hydroxyquinoline Template

The introduction of substituents on bare heterocyclic scaffolds can selectively be achieved by directed C−H functionalization. However, such methods have only occasionally been used, in an iterative manner, to decorate various positions of a medicinal scaffold to build chemical libraries. We herein report the multiple, site selective, metal‐catalyzed C−H functionalization of a “programmed” 4‐hydroxyquinoline. This medicinally privileged template indeed possesses multiple reactive sites for diversity‐oriented functionalization, of which four were targeted. The C‐2 and C‐8 decorations were directed by an N‐oxide, before taking benefit of an O‐carbamoyl protection at C‐4 to perform a Fries rearrangement and install a carboxamide at C‐3. This also released the carbonyl group of 4‐quinolones, the ultimate directing group to functionalize position 5. Our study highlights the power of multiple C−H functionalization to generate diversity in a biologically relevant library, after showing its strong antimalarial potential. The introduction of substituents on a “programmed” 4‐hydroxyquinoline was selectively achieved by directed multiple C−H functionalizations. It could be decorated on four positions, successively at C‐8, C‐2, C‐3 and C‐5, three of which by using transition metal‐catalyzed reactions. Our study highlights the power of multiple C−H functionalization to generate diversity in a biologically relevant library, after showing its strong antimalarial potential.