Copper-catalyzed direct synthesis of furans and thiophenes via decarboxylative coupling of alkynyl carboxylic acids with H2O or Na2S

2,5-Diaryl-substituted furans were synthesized from the copper-catalyzed decarboxylative coupling of aryl-substituted aryl propiolic acids in the presence of H2O. The homocoupling of alkynyl carboxylic acids provided 1,4-diaryldiynes, which then reacted with H2O to give the desired furans through cyclization. Addition of the copper catalyst was critical, and the addition of a ligand increased the yield of products in both the homocoupling and cyclization reactions. In addition, thiophenes could be obtained when the reaction was conducted in the presence of Na2S.

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