Mild Decarboxylative Allylation of Coumarins

Allyl esters of 3-carboxylcoumarins undergo facile decarboxylative coupling at just 25-50 degrees C. This represents the first extension of decarboxylative C-C bond-forming reactions to the coupling of aromatics with sp(3)-hybridized electrophiles. Finally, the same concept can be applied to the sp(2)-sp(3) couplings of pyrones and flavones. Thus, a variety of biologically important heteroaromatics can be readily functionalized without the need for strong bases or stoichiometric organometallics that are typically required for more standard cross-coupling reactions.