Table 4. Enantioselective coupling of indoles to aldehydes using O₂ as the terminal oxidant ^a .

^aPerformed on a 0.10 mmol scale under O₂: 0.20 equiv. tBuONO, 2.0 equiv. H₂-DDQ in 0.4 mL CH₂Cl₂. After 1.5 h, the solvent was removed via evaporation and added portion-wise to a second vial containing 1.0 equiv. 1, 5.0 equiv. 2, 0.20 equiv. 3f, 1.5 equiv. acid, and 0.4 mL CH₂Cl₂ under Ar. Reactions were run for 3 h.