A wide variety of chiral ligands reported in asymmetric NHK reactions were evaluated (Table , top right, see SI for full listing), including salen ligand L1, Nakada's ligand L2 and BOX ligand L3. We were pleased to determine that the chiral sulfonamide ligands (L4-L9) initially introduced by Kishi et al., gave the most promising asymmetric induction. As a result of extensive screening of Kishi-type ligands (>40 ligands, See SI), the R substituent on the aniline was found to play a crucial role wherein the (+)-menthol substituent (L6) enhanced the ee value to 67% compared to a simple methyl group (L4, 1% ee) or a cyclohexyl group (L5, 16% ee). Thus, we evaluated several larger substituents at this position including (+)-8-phenylmenthol 21 (L7), which dramatically improved the ee value to 90%. However, an even more hindered variant containing a 2-naphthyl substituent (L8) did not form the required complex presumably due to its inability to coordinate to the Cr(II) center.