(Diethylamino)difluorosulfonium tetrafluoroborate(Xtalfluor-E,DAST difluorosulfinium salt) is a convenient crystalline highly chemoselective reagent for nucleophilic (deoxo)fluorination with a broad substrate scope and better safety profile like: air stable solid, enhanced thermal stability than DAST or DeoxoFluor, compatibility with glass due to no-generation of free HF under anhydrpous conditions, and simple work-up procedure, etc..
Aminodifluorosulfinium Tetrafluoroborate Salts as Stable and Crystalline Deoxofluorinating Reagents. 
Aminodifluorosulfinum Salts: Selective Fluorination Reagents with Enhanced Thermal Stability and Ease of Handling. 
 F. Beaulieu, et al, Org. Lett. 2009, 11(21), pp 5052-5053.
 A. L'Heureux, et al, J. Org. Chem. 2010, 75(10), pp 3401-3411.