Ligands strongly promote the copper-mediated oxidative coupling (modern Ullmann) reaction of vinylboronate esters and alcohols for the synthesis of vinyl ethers. We found that alkenes and alkynes have a p-ligand effect that enhances this reaction. Furthering this unusual application of p-ligands, allenes were found to facilitate the desired transformation with improved yields as well as overcome limitations in reaction scope. Allenes are proposed to assist the disproportionation and reductive elimination mechanistic steps by acting as p-Lewis bases to Cu(I) and Cu(III) intermediates. Experimental observations correlated exceptionally well with computational studies.

Allene ligands in copper-mediated cross-coupling reactions

243rd National Meeting (2012)

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