An Aminocatalyzed Stereoselective Strategy for the Formal α-Propargylation of Ketones.

A two-step reaction sequence is described for the asymmetric formal α-propargylation of ketones. This approach takes advantage of an aminocatalyzed conjugate addition of ketones to alkylidene isoxazol-5-ones, followed by a controlled nitrosative degradation event. The target compounds can be accessed in broad scope, in moderate to good yields, perfect diastereocontrol and good to excellent enantioselectivity.