1,4-Benzothiazepines via Nucleophilic Catalysis

Significance

A new methodology utilizing fluoride ion as a nucleophilic catalyst was applied in the synthesis of 1,4-benzothiazepines starting from enantiopure cyclic sulfenamides and electron-deficient acetylenes. The reaction was reported to function also with phosphine catalysts (Ph₃P being the best), but in this case one needs equimolar amounts of the phosphine and the yields are slightly lower than those catalyzed with CsF (70% for the former [100 mol%], 81% for the latter [10 mol%]). The yields could be slightly (92% vs. 81%) improved by using 200 mol% CsF, but this is not economically useful and all the reported reactions were conducted with 10 mol% of catalyst. Even though only apparent from the supporting information, the enantiopurity of the starting materials is retained in the reaction. Yields in the reaction range from moderate to good and the substrate scope was limited.