Issue Date: October 10, 2016
Fluoroamide fluorinates itself
When it comes to fluorination of C–H bonds, chemists typically select one reagent to supply the fluorine and must decide whether the target substrate molecule requires a directing group or not to help activate the desired C–H bond and point the fluorine in the right direction. Brian J. Groendyke, Deyaa I. AbuSalim, and Silas P. Cook of Indiana University, Bloomington, have reduced the number of decisions to be made by developing a fluoroamide reagent that acts as the fluorine source and provides its own directing group to fluorinate itself (J. Am. Chem. Soc. 2016, DOI: 10.1021/jacs.6b08171). Undirected C–H fluorinations generally are catalyzed radical reactions that don’t provide optimal C–H bond selectivity, the researchers point out. Directed approaches offer precise targeting, but they remain limited in the types of functionalized molecules that can be used as the substrates and typically require a costly palladium catalyst. The researchers found they could overcome those limitations with fluoroamides made by simply treating a parent amide with N-fluorobenzenesulfonimide. Adding low-cost iron triflate to functionalized benzylic fluoroamides promotes iron-mediated fluorine transfer under mild conditions to make fluorinated benzylic amides. The team suggests this new method could be beneficial in selectively fluorinating molecules during the late stages of complicated pharmaceutical syntheses.
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