Reactions of Alkylidenetriphenylphosphoranes with Sulfur

Reaction of diarylmethylenetriphenylphosphoranes with sulfur gave thiobenzophenones and triphenylphosphine sulfide in good yields. Reaction of benzylidenetriphenylphosphoranes with sulfur gave triphenylphosphine sulfide and 5,7-diphenyl-l,2,3,4,6-pentathiepane. More active alkylidenetriphenylphosphoranes such as isopropylidene- or sec-butylidenetriphenylphosphorane gave the corresponding phosphonium betaine containing sulfur atoms or phosphonium salt produced through air oxidation and hydrolysis of the betaine. α-Benzoylbenzylidenetriphenylphosphorane did not react with sulfur. Reactivity of alkylidenephosphoranes toward sulfur was briefly discussed.