Pentafluorosulfanylbenzene

Pentafluorosulfanylbenzene, or phenylsulfur pentafluoride, is an organosulfur compound with the formula C₆H₅SF₅. It is colorless liquid with high chemical stability.

Reactivity

Pentafluorosulfanylbenzene possesses high chemical stability under a wide range of conditions including oxidizing, reducing, strongly acidic and strongly basic environments. For example, it does not react with a refluxing solution of sodium hydroxide in aqueous ethanol, but it can react with concentrated sulfuric acid at elevated temperatures.
The pentafluorosulfanyl group is a strong electron withdrawing group, and leads to electrophilic aromatic substitution reactions at the meta position.

Synthesis

Pentafluorosulfanylbenzene was originally synthesized by fluorination of diphenyl disulfide by AgF₂. Even with xenon difluoride, the method suffers from low yield. Contrariwise, using dichlorine as oxidant and a fluoride salt as fluorine source generally gives excellent yields.
Better techniques add the pentafluorosulfur moiety, then aromatize the ring. The simplest case dehydrogenates the corresponding dihydrobenzene from a Diels-Alder cycloaddition: H2C=CH-CH=CH2 + F5SC#CH -> F5SC6H7F5SC6H7 -> F5SC6H5 + H2 A more modern technique instead adds SF₅Cl radically to a dichlorocyclohexene, then dehydrohalogenates.