Scheme 2.

Substrate scope of chiral CF₂-substituted aziridines from PhSO₂CF₂CHN₂. General reaction conditions: Aryl glyoxal monohydrate (1, 0.3 mmol), 2a (41 mg, 0.33 mmol), COOH-BA (4 mg, 0.024 mmol), and Na₂SO₄ (200 mg) were stirred in toluene (2 mL) at rt for 30 min, then CDSI-4 (12 mg, 0.015 mmol) and Ps-DFA 3 (105 mg, 0.45 mmol) were added and the mixture was reacted at rt for 24 hours unless otherwise annotated. The yields are those of isolated products, and the dr was determined by ¹⁹F NMR analysis of the crude mixture. The results in parentheses are those of isolated products after the dissolution–filtration process: The corresponding CF₂-functionalized aziridine 4 was dissolved in isopropanol (0.05–0.2 mL/mg) with the help of ultrasound, followed by filtration, and the obtained solution was concentrated to give 4 with increased ee and dr values. ^a0.006 mmol of COOH-BA was employed. ^bThe reaction was operated at 45 °C for 24 h.