Comparative Study of Copper- and Silver-Catalyzed Protodecarboxylations of Carboxylic Acids

The protodecarboxylation of aromatic carboxylic acids by various copper and silver catalysts is investigated with the help of density functional calculations and experimental studies. The computational results reveal that the catalytic activity of copper(I)-1,10-phenanthroline catalysts increases with the introduction of electron-rich substituents at the phenanthroline ligand. They also predicted that for some substrates, silver complexes should possess a substantially higher decarboxylating activity than copper, which is confirmed by experimental studies, leading to the discovery of a silver(I) catalyst that effectively promotes the protodecarboxylation of various carboxylic acids at temperatures in the range of 80-120 degrees C more than 50 degrees C below those of the best known copper(I) catalyst. The scope of the new system complements that of the copper(I)-based method as it includes benzoates for example, with halogen or ether groups in the ortho positions.