Fluorine Chemists Strike Again

Fluorine chemistry has flourished during the past few years as organic chemists have been pressed to find easy, safe, and affordable fluorination reactions for making drug and agrochemical candidates. In the latest example, Patrick S. Fier and John F. Hartwig of the University of California, Berkeley, have created a method for selective C–H fluorination of nitrogen heterocycles (Science 2013, DOI: 10.1126/science.1243759). Heterocycles such as 2-fluoropyridines are highly sought after because their electronic properties enable them to readily undergo further reactions to prepare more complex derivatives and to help improve the potency of drugs. But fluorinated pyridines haven’t been readily available. Fier and Hartwig took inspiration from the classic Chichibabin pyridine amination reaction, in which sodium in NaNH₂ binds to the ring nitrogen and then activates an adjacent C–H bond to add NH₂ to the carbon. In the new work, the researchers used AgF₂, whereby the silver binds to nitrogen and assists in installing fluorine on the adjacent carbon (shown). “This reaction will find immediate use because it is so easy to perform and provides access to high-value fluorinated heterocycles that are otherwise cumbersome to come by,” says organofluorine synthesis expert Tobias Ritter of Harvard University.