Nitrogen-Based Fluorinating Agents
Mechanism + Description

N–F reagents provide a source of F+ and essentially react as electrophilic sources of fluorine reacting with electron-rich unsaturated bonds.
General comments
A range of N centred F+ reagents are available to use in electrophilic fluorination as alternatives to F2. These reagents will attack neutral electron-rich unsaturated bonds. Less reactive centers can be converted to carbanions prior to reaction with the fluorinating agent. N-F reagents can be used in conjunction with Pd catalysis to fluorinate aryl C-H bonds in C-H activation chemistry.
Selectfluor fluorinates a variety of ketones, thioethers, alkenes and aromatic substrates. It can also be used in decarboxylative fluorinations of aliphatic carboxylic acids. Selectfluor may also serve as effective sources of atomic fluorine in the free radical hydrofluorination of unactivated alkenes.
Key references
In the presence of chiral ligands/complexes, construction of chiral C-F bonds is feasible:
Relevant scale up example
Königsberger, K. Chen, G.-P.; Vivelo, J.; Lee, G.; Fitt, J.; McKenna, J.; Jenson, T.; Prasad, K.; Repič, O. Org. Process Res. Dev. 2002, 6, 665-669.
Experimental
270g scale
Umemoto, T.; Tomita, K.; Kawada, K. Org. Synth. 1990, 69, 129.
Experimental
7g scale
Briner, P. H.; Fyfe, M. C. T.; Martin, P.; Murray, P. J.; Naud, F.; Procter, M. J. Org. Process Res. Dev. 2006, 10, 346-348.
Experimental
1kg scale
Green Review
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Atom efficiency (by-products Mwt)
Poor atom economy reagents being surrogates for F2. However, being stable crystalline substances they offer reduced reactivity and operational simplicity compared to F2 gas. The byproducts are conjugate acids of the nitrogen base. Fluoropyridinium salts offer the best atom efficiency in this class. - Safety Concerns
These materials require less specialised handling and containment compared to F2. With these reagents, materials compatibility can be an issue, and these F+ reagents can react violently with certain solvents and other organic materials. - Toxicity and environmental/aquatic impact
High concentrations are damaging to all lifeforms, but these materials are too reactive to persist in the environment. Any long term issues would reflect the ecotoxicity of the conjugate nitrogen bases and any anions used. Trifluoromethanesulphonate (triflate) is persistent. - Cost, availability & sustainable feedstocks
Most are available in bulk but are expensive reagents. - Sustainable implications
These are poor atom efficiency reagents that come from F2. They are high LCI materials.