Highly Improved Copper-Mediated Michael Addition of Ethyl Bromodifluoroacetate in the Presence of Protic Additive

Copper-mediated Michael addition of ethyl bromodi­fluoroacetate to Michael acceptors is accompanied by the formation of a substantial amount of byproducts. Elucidation of their structure hinted the cause of their formation, from which we discovered a highly improved and robust protocol by treatment with protic additives such as H₂O and AcOH. This modification led to significant increase of yield with concomitant decreased use of reagent.