A new methodology, using fluoride ion as a nucleophilic catalyst, was applied for the synthesis of enantiopure 1,4-benzothiazepine from cyclic sulfenamide and electron-deficient acetylene, with high efficiency and atom economy. ... However, no reaction occurred when sulfenamide 1a was submitted to DMAD in acetonitrile by heating (Table 1, entry 1) or in the presence of Lewis acids (entry 2). ... Unless otherwise indicated, all reactions were performed at 0.1 M ...