Synthesis of 3-(Arylsulfonyl)-3-pyrrolines from Allenyl Sulfonamides by Silver Ion Catalysis

Treatment of allenyl sulfonamides with catalytic amounts of silver fluoride in acetonitrile at reflux afforded the corresponding 3-sulfonyl-3-pyrrolines in excellent yields by intramolecular hydroamination via a 5-endo-trig cyclization. The starting allenyl sulfonamides were prepared by lithiation of allenic sulfones and trapping with various N-sulfonylimines.