Enantioselective Synthesis of N-H-Free 1,5-Benzothiazepines.

An enantioselective sulfa-Michael-cyclization reaction was developed for the synthesis of 1,5-benzothiazepines with versatile pharmacological activities. The reaction between 2-aminothiophenol and α,β-unsaturated pyrazoleamides gave direct access to N-H-free 1,5-benzothiazepines in the presence of a chiral N,N'-dioxide/Yb(OTf)3 complex. Excellent enantioselectivities (up to 96 % ee) and high yields (up to 99 %) were obtained for a broad range of substrates under mild reaction conditions. This method provided a facile approach to the antidepressant drug (R)-(-)-Thiazesim.