1-Alkyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane salts: a novel family of electrophilic fluorinating agents

The effect of the reaction conditions on the course of the reactions of hindered phenols with N-F reagents

“…We further investigated the effect of solvent polarity and the presence of an external nucleophile on the course of the reaction of hindered phenol 1 with F-TEDA-BF 4 or NFTh, and found that during reaction of the tested phenol in methanol at room temperature the reagent was ether derivative 6b was achieved when at least a five fold molar excess of methanol was present in the reacting mixture, while by lowering its concentration, the relative amount of fluorinated products 3, 4, and 5 increased. Under optimised reaction conditions 1 was readily transformed to the corresponding para quinol ethers also when ethanol (entry 3, Table), propanol (entry 4) or 1,2-ethanediol (entry 5) were present in the reaction mixture, while in the presence of water the selectivity of the reaction was found to be poor and only a moderate yield of the para quinol derivative was detected among other, mainly fluorinated reaction products 3, 4, and 5.…”

“…2 The introduction of organic molecules incorporating a reactive N-F bond as versatile mild fluorinating reagents 3 in the last decade has had a revolutionary influence on research in the field of the chemistry of organofluorine molecules. Derivatives of the N-fluoro-1,4-diazoniabicyclo[2.2.2] octane salts promoted by Banks 4 possess optimal stability/reactivity characteristics and as easy handling, cost effective, commercially available reagents are convenient for routine laboratory work as well as for large scale applications. 5 The oxidative power of Banks' reagents is lower in comparison with other types of »electrophilic« mild fluorinating reagents (fluoroxy derivatives or xenon fluorides), but is among the highest in the series of N-F reagents.…”

Selective fluorination of natural products

“…The advance in reagents that can react via electrophilic fluorination and embody a certain specificity of conditions has not only improved the selectivity of fluorination but has also improved the tolerance of functional groups. 13 The developments of reagents such as N-fluoropyridium salts (FP-T300) 14 , N-fluorobis(phenyl)sulfonimide (NFSI) 15 , 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo-[2.2.2] octane bis(tetrafluoroborate) (Selectfluor®, F-TEDA-BF4), 16 and derivative F-TEDA-PF6 17 have been great innovations to the introduction of a fluorine atom (Figure 3). …”

Selectfluor: Mechanistic Insight and Applications

“…Selectfluor, [15,17] an exceptionally stable, virtually nonhydroscopic crystalline solid, represents a significant improvement on traditional electrophilic fluorinating agents, which require special handling and tend to be synonymous with danger. In an extreme experiment to demonstrate its stability (and to satisfy the United States Department of Transportation regarding the risks associated with transporting a potentially dangerous compound), a self-accelerating decomposition temperature (SADT) test was performed, in which a 55-gallon drum filled with selectfluor was heated to 56 8C for 7 days; during this time the temperature remained constant within AE 5 8C.…”

“…[15,17,18] The procedure involves initial alkylation with dichloromethane, which also serves as the solvent, followed by the addition of lithium tetrafluoroborate, yielding 5 a upon filtration. A different counterion can be incorporated during fluorination by using one of three methods.…”