Copper-catalyzed nondecarboxylative cross coupling of alkenyltrifluoroborate salts with carboxylic acids or carboxylates: synthesis of enol esters

Org Lett. 2013 Jun 21;15(12):3150-3. doi: 10.1021/ol4013712. Epub 2013 Jun 4.

Abstract

A mild copper-catalyzed Chan-Lam-Evans type cross-coupling reaction for the regioselective and stereospecific preparation of (E)- or (Z)-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.