Microwave fluorination: a novel, rapid approach to fluorination with Selectfluor®

N-Fluorobenzenaminium tetrafluoroborate generated in situ by aniline and Selectfluor as a reusable catalyst for the ring opening of epoxides with amines under microwave irradiation

“…1). The byproduct of this reaction, 1-(chloromethyl)-4-aza-1-azonia-bicyclo[2.2.2]octane tetrafluoroborate (2), was confirmed by the presence in the 1 H NMR spectrum of peaks at 3.23 (t, J = 8.0 Hz), 3.50 (t, J = 8.0 Hz) and 5.03 (s) ppm, the spectrum was identical to that of the separately synthesized pure compound 2 (see ESI †). The 1 H NMR spectra of in situ generated catalyst 1 and isolated N-fluorobenzenaminium tetrafluoroborate (1) (see ESI †) are also identical (Fig.…”

“…Selectfluor (1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2] octane bis(tetrafluoroborate)) is a commercially available, exceptionally stable and virtually nonhygroscopic crystalline solid which is widely used for the electrophilic fluorination of electron-rich carbon centers. 1,2 Its electrophilic and oxidative characteristics make it a useful catalyst for the cleavage of electron-rich protecting groups, such as p-methoxybenzylidene (PMP), tetrahydropyranyl (THP) ethers, 1,3-dithianes, the deprotection of silyl ethers and the ring opening of epoxides with ammonium thiocyanate (Scheme 1). [3][4][5] The ring opening of epoxide with an amine as a nucleophile is an important route for the synthesis of β-amino alcohols.…”

Solvent‐Free Fluorination of Electron‐Rich Aromatic Compounds with F‐TEDA‐BF4: Toward “Dry” Processes

“…[8a], [8b], The replacement of volatile organic solvents with more “green” alternatives is one of the most demanding areas of research , . Recent advances in “green” fluorination with NF reagents includes reactions in room‐temperature ionic liquids (ILs), IL/alcohol mixtures,, supercritical carbon dioxide, water,, poly(ethylene glycol) 400 (PEG‐400), and H 2 O/PEG‐400, as well as the use of microwave irradiation for low energy consumption . However, the most significant decrease of the environmental footprint of most industrial processes would be the complete elimination of the solvent.…”

Microwave-assisted rapid electrophilic fluorination of 1,3-dicarbonyl derivatives with Selectfluor®

“…Since significant rate acceleration for reactions carried out in a conventional microwave oven were first observed in 1986, microwave irradiation has found increasing application in organic synthesis [18][19][20]. Recently, microwave-assisted fluorination of aromatic rings using 1 was reported [21]. Considering the slow fluorination rates of some 1,3-dicarbonyls with 1, we were interested in examining the impact of microwave irradiation on yields and reaction times when mono and/or difluorinated compounds were the desired products.…”