Decarbonylative Sonogashira Cross-Coupling: Fruitful Marriage of Alkynes with Carboxylic Acid Electrophiles.

The Sonogashira cross-coupling is one of the most fundamental C-C bond forming reactions, wherein the strategic value of the alkyne moiety has found widespread application at the frontiers of organic chemistry, materials science and drug discovery as the cornerstone building block of chemical synthesis. Although traditional variants of Sonogashira cross-coupling involve aryl halides and pseudohalides as electrophiles, recently, tremendous advances have been made in the unconventional disconnection exploiting common carboxylic acids by decarbonylation/transmetalation pathway. This manifold (1) permits to take advantage of carboxylic acids as a ubiquitous class of substrates in organic synthesis that are derived from an orthogonal pool of precursors to aryl halides and pseudohalides, (2) combines the benefits of the palladium catalyzed C(sp2)-C(sp) coupling of terminal alkynes with the inherent presence of the carboxylic acid moiety in pharmaceuticals, natural products and organic materials. In this highlight article, we summarize recent progress generated by the decarbonylative Sonogashira cross-coupling of carboxylic acid electrophiles to produce arylalkynes and conjugated enynes as a novel avenue for chemical synthesis, whereby a large number of chemical reactions critically rely on transformations of alkynes.