Abstract

Aims: Using Selectorfluor® for the oxidation of urazoles and sulfides as well as the oxidation of alcohols under mild conditions.

Background: [1-Chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane-bis(tetrafluoroborate)] so-called Selectorfluor®, is a reagent/catalyst that is donor of the electrophilic fluorine atom. Selectorfluor ® is a colorless salt which was first introduced in 1992. This year, Banks et al. prepared a salt from the reaction of dichloromethane with dabco and sodium tetrafluoroborate, and then reacted it with fluorine gas to prepare the Selectorfluor®.

Objective: Unlike the highly hazardous F2, the Selectorfluor® is a stable, non-hygroscopic, easy to handle and commercially available reagent that has many applications in organic reactions.

Methods: Substrate [alcohols, urazoles or sulfides (1 mmol)] was added to the mixture of Selectorfluor ® (0.708 g, 2 mmol), KBr (0.236 g, 2 mmol), and 0.2 g wet SiO₂ (50%). The mixture was ground with a mortar and pestle for 10-15 minutes. Then, the product was extracted with CH₂Cl₂ (2×10 mL). The solution was dried with anhydrous sodium sulfate and filtered again. Simple distillation of the CH₂Cl₂ gave the crude product. Aldehyde/ketones and sulfoxides were purified by short column chromatography on silica gel with EtOAc/n-hexane (1:3 to 1:5). Urazoles were purified by the sublimation method.

Results: Some advantages of these oxidation reactions using the Selectorfluor®/KBr system are: a) both reagent and catalyst are safe and easy to handle; b) the procedure is solvent-free; c) the reaction is carried out at room temperature; d) yields are good to excellent; e) work-up is convenient since the reagent/catalyst residue is ionic and insoluble in the organic solvents.

Conclusion: Selectorfluor® is a safe and stable reagent that is easy to work with, although it is slow and lazy in reaction, and it cannot react well at room temperature. The literature survey shows that the best conditions for a reaction are acetonitrile reflux and that the solvent-free is not very desirable conditions.

Keywords: Selectfluor, oxidation, urazoles, alcohols, sulfides, solvent free.