Enantioselective Acylphosphonylation—Dual Lewis Acid–Lewis Base Activation of Aldehyde and Acylphosphonate

Acetoxyphosphonates were obtained by a one-step procedure consisting of reaction of diethyl acetylphosphonate with prochiral aldehydes in the presence of a catalytic system comprising a chiral Lewis acid, an achiral Lewis base, and a Brønstedt base. Best results were obtained using a tridentate Schiff base aluminum(III) Lewis acidic complex, 1H-1,2,3-benzotriazole, and a tertiary amine such as DBU. The target compounds were in most cases obtained in high yields, but with moderate enantiomeric ratios (up to 78:22).