Sulfur hexafluoride is added to the fluorination tool box

In the ongoing quest for developing milder, safer, and more versatile fluorinating reagents, chemists at Massachusetts Institute of Technology have developed the first general strategy for using sulfur hexafluoride in organic synthesis (Angew. Chem. Int. Ed. 2016, DOI: 10.1002/anie.201608792). Sulfur hexafluoride, SF₆, is a colorless, odorless, inert gas that is widely used as an insulator in electrical equipment such as high-voltage circuit breakers and as a tracer gas to check ventilation systems. But because SF₆ has the highest known global warming potential for any compound, these applications are being phased out. The cheap gas could still be used to an advantage in large-scale syntheses in which SF₆ is destroyed. MIT’s T. Andrew McTeague and Timothy F. Jamison may have found one option. The team created a process in which an iridium photocatalyst transfers an electron to SF₆ to create a reactive radical species. The radical subsequently disintegrates, providing a source of nucleophilic fluorine. In a test reaction, the researchers used SF₆ for the deoxyfluorination of allylic alcohols to form linear and branched fluorinated olefins. To improve upon the yield and product throughput, McTeague and Jamison further devised a continuous-flow process—a specialty of the Jamison lab—for the SF₆ deoxyfluorinations. Overall, the results suggest that SF₆ could replace some costly and/or hazardous fluorinating reagents.