The hydroamination of alkenes with sulfonamides catalyzed by the recyclable silica gel supported triflic acid

The vast applications of triflic acid (TfOH) in catalysis are severely limited by its corrosive and fuming properties. Immobilization of TfOH on silica gel well solves these problems and affords efficient recovery and reusability of TfOH. Two types of supported TfOH, the prepared silica gel supported TfOH and the in situ silica gel adsorbed TfOH, both exhibit good catalytic activity and reusability in the hydroamination of alkene with sulfonamide. The in situ silica gel adsorbed catalyst has been used for 5 runs with maintained reactivities and yields, which are superior to the performance of the prepared silica gel supported TfOH. For a series of alkenes and various sulfonamides, the heterogeneous hydroamination reactions catalyzed by both types of silica gel supported TfOH to afford similar moderate to excellent yields.