Highly Stereoselective Catalytic Carbocupration of Alkynoates

Significance

While stoichiometric carbocupration of alkynes was first reported by E. J. Corey about 40 years ago, this publication describes the first both diastereoselective and catalytic method for the addition of Grignard reagents to alkyno­ates. By choosing the additive (TMSCl or TMSOTf) and the proton source (NH₄Cl or TFA), the reaction can be switched to the formation of Z- or E-products with high stereoselectivity. Addition of an electrophile allows the preparation of stereodefined trisubstituted acrylates.