Catalytic Carbocupration of Alkynoates

Significance

The synthesis of stereodefined, substituted alkenes through a copper-catalyzed carbocupration of propiolates and subsequent O-to-C silyl migration of TMS allenolates is described. Addition of cuprates across propiolates and other Michael acceptors is a well-known strategy (see Review below), although catalytic variants of this reaction are less common. This work follows up on the authors’ studies of similar carbocuprations of alkynoates usually followed by trapping with external electrophiles (Org. Lett. 2008, 10, 1649), and herein the silane rearrangement is explored in more detail. The use of catalytic copper and the compatibility of TMSOTf and RMgBr under the reaction conditions are note­worthy.