Copper-catalyzed cascade radical cyclization of alkynoates: construction of aryldifluoromethylated coumarins.

A mild and simple method is reported for the construction of 3-difluoroarylmethylated coumarins using α,α-difluoroarylacetic acids as an easily handled difluoromethyl source in reaction with ester 3-arylpropiolates under the promotion of copper. The reaction involves a proposed radical-triggered domino decarboxylative aryldifluoromethylation/5- cyclization/ester migration process that directly forms Csp-CFAr and C-C bonds with good functional group tolerance.