Table 3. Substrates scope of aldehydes*.

*Unless otherwise specified, the reaction of 1a (0.1 mmol), 2a (2.0 mmol), DDQ (1.4 equiv), CP3 (10 mol%) and 4 Å MS was carried out in 4.0 ml CHCl₃ at 0 °C for 96 h under Ar.

†At 25 °C.