This tutorial review provides a comparison between the concepts of catalytic decarboxylative and decarbonylative couplings for the ipso-substitution of carboxylate groups, and illustrates their potential benefits over alternative C-C bond-forming reactions. Redox-neutral decarboxylative reactions allow generating organometallic species with nucleophilic reactivity via the extrusion of carbon dioxide from metal carboxylates. Such C-C bond activating processes provide a way of employing carboxylate salts as substitutes for the traditional sources of carbon nucleophiles, i.e. stoichiometric organometallic reagents. If the decarboxylation of carboxylic acids is performed under oxidative conditions, organometallic species with electrophilic reactivity are obtained instead. These can alternatively be accessed via the extrusion of carbon monoxide from acyl-metal species generated via the oxidative addition of activated carboxylic acid derivatives (e.g. acid chlorides, anhydrides or esters) to metal complexes. In the latter two reaction types, carboxylic acids thus become substitutes for organohalides. The complementary redox-neutral and oxidative decarboxylative and decarbonylative reaction modes allow the broad use of carboxylic acids as substrates in C-C bond-forming reactions. Their applicability, scope and limitations are discussed using the examples of Heck reactions, cross-couplings and direct arylations.

A silver-based catalyst system has been discovered that effectively promotes the protodecarboxylation of various carboxylic acids at temperatures of 80-120 degrees C--more than 50 degrees C below those of the best known copper catalysts.

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 °C—more than 50 °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.

A highly effective

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