Phosphine-catalyzed asymmetric synthesis of beta-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 beta-lactones (14 examples) is reported. The BINAPHANE catalytic system displays excellent enantioselectivity (seven examples with ee >or=90%) and high diastereoselectivity favoring formation of the trans-diastereomer (nine examples with dr >or=90:10).