Treatment of cis‐[Ru(bpy)2Cl2]⋅2 H2O or Δ/Λ‐[Ru(bpy)2(py)2]2+ (bpy=2,2′‐bipyridine, py=pyridine) with the prochiral thioether ligands 2‐alkylthiobenzoic acid (HOSR) produces the corresponding thioether complexes rac‐[Ru(bpy)2(OSR)](PF6) (R=Me (rac‐1), iPr (rac‐2), 2‐benzylthiobenzonate (Bn) (rac‐3)) and Δ/Λ‐[Ru(bpy)2(OSR)](PF6) (R=Me (Δ‐1/Λ‐1), iPr (Δ‐2/Λ‐2), Bn (Δ‐3/Λ‐3)) with retention of the configurations at chiral metal centers. In situ oxidation of the thioether complexes by meta‐chloroperoxybenzoic acid provides the corresponding sulfoxide complexes rac‐[Ru(bpy)2(OSOR)](PF6) (OSOR is 2‐alkylsulfinylbenzonate, R=Me (rac‐1 a), iPr (rac‐2 a), Bn (rac‐3 a)), Δ‐[Ru(bpy)2{(R)‐OSOR}](PF6) (R=Me (Δ‐1 a), iPr (Δ‐2 a), Bn (Δ‐3 a)), and Λ‐[Ru(bpy)2{(S)‐OSOR}](PF6) (R=Me (Λ‐1 a), iPr (Λ‐2 a), Bn (Λ‐3 a)) in yields of 95 % with 98 % ee values. The absolute configurations at the metal centers and sulfur atoms were determined by means of X‐ray crystallography. The results indicate that the configurations of the metal centers are retained and have the function of controlling sulfoxide chirality during the oxidation process. The Δ metal‐centered configuration enantioselectively generates an R‐configuration sulfoxide, and the Λ configuration enantioselectively forms an S‐configuration sulfoxide in the course of the in situ oxidation reaction, thereby resulting in a predetermined chirality of the sulfoxide ligands. The predetermined chirality of sulfoxides (S)‐HOSOR and (R)‐HOSOR were obtained by the treatments of the corresponding sulfoxide complexes Δ‐[Ru(bpy)2{(R)‐OSOR}](PF6) and Λ‐[Ru(bpy)2{(S)‐OSOR}](PF6) with trifluoroacetic acid in yields of 90 % with 83.5–92.9 % ee values.

The enantioselective oxidation synthesis of chiral modafinil acid and its analogues with high enantiomeric excess has been developed by means of a chiral‐at‐metal strategy. Treatment of ruthenium complexes cis‐[Ru(bpy)2Cl2] or Δ/Λ‐[Ru(bpy)2(MeCN)2](PF6)2 (bpy is 2,2′‐bipyridine) with the appropriate prochiral thioether ligands afforded thioether complexes rac‐1, Δ/Λ‐1, rac‐2, Δ/Λ‐2, rac‐3, and Δ/Λ‐3. Diastereoselective oxidation of the thioether complexes in situ produced the corresponding sulfoxide complexes rac‐1a, Δ/Λ‐1a, rac‐2a, Δ/Λ‐2a, rac‐3a, and Δ/Λ‐3a. The configuration at the metal center in each case is stable during the coordination and oxidation reactions, and dictates the chirality of the sulfoxide ligand in the oxidation process. The chiral modafinil acids were obtained with ee values greater than 98 % upon their removal from the corresponding sulfoxide complexes in the presence of TFA/MeCN. Moreover, the chiral ruthenium precursors Δ/Λ‐[Ru(bpy)2(MeCN)2](PF6)2 are recyclable and reusable with complete retention of the configurations.