Asymmetric Synthesis of Highly Substituted β-Lactones through Oxidative Carbene Catalysis with LiCl as Cooperative Lewis Acid

The reaction of enals with beta-diketones, beta-ketoesters, and malonates bearing a beta-oxyalkyl substituent at the alpha-position by oxidative NHC catalysis to provide highly substituted beta-lactones is described. Reactions occur with excellent diastereo- and enantioselectivity. The organo cascade comprises two C-C bond formations and one C-O bond formation. Up to four contiguous stereogenic centers including two fully substituted stereocenters are formed in the cascade.