Programmed multiple C–H bond functionalisation of the privileged 4-hydroxyquinoline template

The introduction of substituents on bare heterocyclic scaffolds can selectively be achieved by directed C–H functionalisation. 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 functionalisation of a "programmed" 4-hydroxyquinoline. This medicinally privileged template indeed possesses multiple reactive sites for diversity-oriented functionalisation, 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 functionalise position 5. Our study highlights the power of multiple C–H functionalisation to generate diversity in a biologically relevant library, after showing its strong antimalarial potential.