Substrate scope of various alcohols and aryl aldehydes^a.

^aReaction conditions: aryl aldehyde 1 (1.0 mmol), VB1 (0.2 mmol), and DABCO (2.0 mmol) in alcohol 2 (2.0 mL) at 80 °C (oil bath) for 12–24 h under air; isolated yields.