Metal-Catalyzed Ionic Decarboxylative Cross-Coupling Reactions of C(sp3) Acids: Reaction Development, Mechanisms and Application

The direct transition metal-catalyzed conversion of carboxylic acid groups into other C–C or C–X bonds provides a complementary bond disconnection to traditional cross-coupling manifolds. Decarboxylative coupling strategies can be divided into two mechanistic frameworks: decarboxylative homolysis processes that generate radicals and decarboxylative heterolysis processes that generate carbanions. The challenge of both inducing decarboxylation with unmodified substrates and enabling efficient interception by a suitable transition metal complex has made achieving general approaches to catalytic cross-couplings of carboxylic acids elusive. Thus, more wasteful indirect strategies involving pre-activation of the acid unit are more common. This perspective article highlights recent work in the area of metal-catalyzed ionic decarboxylative cross-coupling reactions of unmodified C(sp3) carboxylic acids. In these processes, the carboxylic acid unit serves as a surrogate for nucleophiles normally generated by deprot...