We followed the initial catalyst hit identification campaign by exploring accessible phosphinate derivatives in an attempt to further improve the catalytic asymmetric reaction (Figure ). Electron-poor (3b), electron-rich (3c), and sterically hindered (3d) aryl derivatives did not influence the catalyst selectivity. Conversely, the relative substituent size of alkyl derivatives significantly impacted enantioselectivity (3e-3g, 69:31 to 96:4 er), with the optimal catalyst being the dicyclohexylphosphinate derivative 3e (96:4 er). Modifications of the C6′-position on the quinoline fragment were also evaluated. The protio derivative 3h gave only moderate enantioselectivity (81:19 er) despite its distal location from the identified key phosphinate group. Installation of bulkier i-PrO or Ph substituents (3i and 3j, respectively), had little impact on enantioselectivity (95:5 to 96:4 er, respectively). Two other aryl substituents gave unpredictable results, with the electron-withdrawing Figure . Exploration of sulfonimidamide substrate scope. (A) Sulfonimidamide substrate scope. Reaction conditions: substrate 1 (1.00 mmol, 1.0 equiv), 2a (3.00 mmol, 3.0 equiv), and catalyst 3e (0.20 mmol, 20 mol %) in THF (20.0 mL, 0.05 M) at -35 °C. a Isolated yield after purification. b er of the isolated product as determined by chiral SFC analysis. c Absolute configuration determined by X-ray crystallographic analysis. (B) PCA of synthetically feasible sulfonimidamides (43.5% of the total variance depicted with two principal components), selected substrates are labeled, and black crosses indicate substrates screened using HTE.