Phosphine-Catalyzed Asymmetric Synthesis of β-Lactones from Arylketoketenes and Aromatic Aldehydes

In this paper, the development of a chiral phosphine-catalyzed formal [2 + 2] cycloaddition of aldehydes and ketoketenes that provides access to a variety of highly substituted β-lactones (14 examples) is reported. The BINAPHANE catalytic system displays excellent enantioselectivity (seven examples with ee ≥90%) and high diastereoselectivity favoring formation of the trans-diastereomer (nine examples with dr ≥90:10).