In our initial study, N-propyl sulfonimidoyl la and phenol 2a were chosen as the model substrates to investigate the optimal reaction conditions. In the presence of MS 4Å and 10 mol% of a stable NHC A, the desired sulfonimidate ester 3a was obtained in 15% yield (Table1, entry1). Pleasingly, with the addition of HOBt (10 mol%) as cocatalyst, the yield Catalyst and additives Solvent t (h) Yield(%) 1 A, 200 mg MS 4Å CH3CN 24 15