Backdoor approach to SF₅ furans

The first examples of pentafluorosulfanyl-substituted furan compounds have been made by two retro-Diels-Alder strategies developed by William R. Dolbier Jr. and his coworkers at the University of Florida (Org. Lett., DOI: 10.1021/ol0622662). Although inorganic SF₅-containing compounds have been known for some time, synthesis of organic SF₅ compounds has been slow to develop because the chemistry of the most useful sources of the SF₅ group, SF₅Cl and SF₅Br, is limited to free-radical addition reactions. In one approach, the researchers added SF₅Cl to a furan-acrylonitrile Diels-Alder adduct and used LiOH to eliminate HCl. They then took advantage of the known reversibility of furan Diels-Alder reactions to thermally dissociate the adduct to form the substituted furan, as shown. In the second approach, an adduct was prepared by adding an SF₅ acetylene compound, CH₃(CH₂)₃C≡CSF₅, to 4-phenyloxazole, a common starting material used to synthesize furans. The researchers believe the two strategies can be used to prepare a variety of SF₅-substituted heterocycles that will be of "special interest" as potential building blocks for pharmaceuticals and agrochemicals.