Divergent Synthesis of 1,2-Benzo[ e]thiazine and Benzo[ d]thiazole Analogues Containing a S-Trifluoromethyl Sulfoximine Group: Preparation and New Properties of the Adachi Reagent.

We report here the preparation of unprecedented analogues of 1,2-benzothiazine and benzoisothiazole incorporating the S-trifluoromethyl sulfoximine group in their core. Using a stable precursor to start, cyclization occurs via a catalytic controlled process. The choice of the catalyst is crucial for selectivity toward the five- or the six-membered ring. Interestingly, one of the benzothiazines can be converted on a gram scale into the trifluoromethylating Adachi reagent. We also disclose the first use of this reagent as a source of radical CF3 under photoredox catalysis. DFT calculations were performed to clarify the cyclization mechanism.