Table 2. Enantioselective coupling of various indoles to aldehyde 1a applying DDQ as the oxidant ^a .

^aPerformed on a 0.10 mmol scale under Ar: 1.0 equiv. 1a, 5.0 equiv. 2, 0.20 equiv. 3f, 1.5 equiv. acid, 1.1 equiv. DDQ (in two portions), and 0.4 mL CH₂Cl₂.

^bAfter 3 h, another 0.50 equiv. of DDQ was added and stirred overnight.