Copper-Catalyzed Nondecarboxylative Cross Coupling of Alkenyltrifluoroborate Salts with Carboxylic Acids or Carboxylates: Synthesis of Enol Esters

A mild copper-catalyzed Chan–Lam–Evans type cross-coupling reaction for the regioselective and stereospecific preparation of (<i>E</i>)- or (<i>Z</i>)-enol esters is described. The method couples carboxylate salts or carboxylic acids with potassium alkenyltrifluoroborate salts in the presence of catalytic CuBr and DMAP with 4 Å molecular sieves under O₂ at 60 °C. Overall, this method demonstrates carboxylic acids as suitable reaction partners for nondecarboxylative copper-catalyzed cross-couplings to form C–O bonds in an Ullmann-like reaction