C–N Coupling of DNA-Conjugated (Hetero)aryl Bromides and Chlorides for DNA-Encoded Chemical Library Synthesis

DNA-encoded chemical library (DECL) screens are a rapid and economical tool to identify chemical starting points for drug discovery. As a robust transformation for drug discovery, palladium-catalyzed C–N coupling is a valuable synthetic method for the construction of DECL chemical matter; however, currently disclosed methods have only been demonstrated on DNA-attached (hetero)­aromatic iodide and bromide electrophiles. We developed conditions utilizing an N-heterocyclic carbene–palladium catalyst that extends this reaction to the coupling of DNA-conjugated (hetero)­aromatic chlorides with (hetero)­aromatic and select aliphatic amine nucleophiles. In addition, we evaluated steric and electronic effects within this catalyst series, carried out a large substrate scope study on two representative (hetero)­aryl bromides, and applied this newly developed method within the construction of a 63 million-membered DECL.