Enantioselective Synthesis of Chiral-at-Sulfur 1,2-Benzothiazines by Cpx RhIII -Catalyzed C-H Functionalization of Sulfoximines.

Sulfoximines with stereogenic sulfur atoms are attractive structural motifs in drug discovery. A direct catalytic enantioselective method for the synthesis of sulfur-chiral 1,2-benzothiazines from readily accessible diaryl sulfoximines is presented. Rhodium(III) complexes equipped with chiral cyclopentadienyl ligands and paired with suitable carboxylic acid additives engage in an enantiodetermining C-H activation directed by the sulfoximine group. Subsequent trapping of the rhodacycle with a broad range of diazoketones gives access to S-chiral 1,2-benzothiazines with synthetically highly attractive substitution patterns in good yields and enantioselectivities.