Josiphos-catalyzed asymmetric homodimerization of ketoketenes.

In this paper the development of a chiral phosphine-catalyzed homodimerization of ketoketenes that provides access to a variety of highly substituted ketoketene dimer β-lactones (11 examples) is reported. The Josiphos catalytic system displays good to excellent enantioselectivity (up to 96% ee). Ring-opening reactions of the enantioenriched ketoketene dimers were also carried out to access 1,3-diketones, enol esters, and β-hydroxyketones with good diastereoselectivity.