Nucleophilic Fluorination of Heteroaryl Chlorides and Aryl Triflates Enabled by Cooperative Catalysis

Aryl and heteroaryl fluorides are growing to be dominant motifs in pharmaceuticals and agrochemicals, yet they are rare in both nature and commodity chemicals. As a consequence, there is an increasingly urgent need to develop mild, cost-effective, and scalable methods for fluorination. The most straightforward route to synthesize aryl fluorides is through the halide exchange "halex" reaction, but conditions, cost, and atom economy preclude most available methods from large-scale manufacturing processes. We report a new approach that leverages the cooperative action of 18-crown-6 ether and tetramethylammonium chloride to catalytically access the reactivity of tetramethylammonium fluoride and achieve halex fluorinations under mild conditions with operational ease. The described methodology readily converts both heteroaryl chlorides and aryl triflates to their corresponding (hetero)aryl fluorides in high yields and purities.