Silver(I) Fluoride-Calcium Fluoride1

AgF/CaF2
(AgF)

[7775-41-9]  · AgF  · Silver(I) Fluoride-Calcium Fluoride  · (MW 126.87) (CaF2)

[7789-75-5]  · CaF2  · Silver(I) Fluoride-Calcium Fluoride  · (MW 78.08)

(fluorination reagent,2 useful for conversion of alkyl halides to alkyl fluorides and for halofluorination of alkenes)

Form Supplied in: white free-flowing granular powder.

Preparative Method: Silver(I) Fluoride is supported on calcium fluoride by slowly evaporating a mixture of silver carbonate, 50% aqueous Hydrofluoric Acid, and CaF2 in water to a dry granular powder.2

Handling, Storage, and Precautions: highly hydroscopic and light sensitive.

Halogen Exchange.

Silver fluoride dispersed on the surface of calcium fluoride shows improved fluoride nucleophilicity for halogen exchange with alkyl and benzyl halides. Thus treatment of 1-bromooctane with AgF/CaF2 in acetonitrile for 30 min at 75 °C affords 1-fluorooctane in 41% yield (eq 1).

This reagent also proves superior to KF/CaF2 and CsF/CaF2, although the presumably high cost of the reagent could outweigh the increase in yield when used on a large scale. A comparative example is shown in eq 2. In general, alkyl iodides give better yields than bromides, which in turn give better yields than chlorides.

Alkene Additions.

Silver fluoride has been used in the presence of a halogen or a suitable N-haloamide for the in situ generation of halogen fluorides XF (X = I, Br, Cl) which add to alkenes.3 Halofluorination of alkenes using the AgF/CaF2 reagent has also been reported.2 Bromofluorination is most effective with 1,3-Dibromo-5,5-dimethylhydantoin (DBH) (eq 3). N-Bromosuccinimide gives poor results, as dibromide byproducts are formed. Iodofluorination is equally effective using either Iodine or N-Iodosuccinimide with AgF/CaF2; the yield of ca. 50% is similar to the literature values (eq 4).3

Related Reagents.

Bromine Monofluoride; Cesium Fluoride; Iodine Monofluoride; Potassium Fluoride.


1. Wilkinson, J. A. CRV 1992, 505.
2. Ando, T.; Cork, D. G.; Fujita, M.; Kimura, T.; Tatsuno, T. CL 1988, 1877.
3. Hall, L. D.; Jones, D. L. CJC 1973, 51, 2902.

Bradley B. Brown

University of California, Berkeley, CA, USA



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