Alkyne Metathesis

Although alkyne metathesis had already been discovered in the late 1960s, the reaction gained preparative significance only much later. Key to success was the design of novel catalyts, which evolved over the years from ill-defined species generated in situ to mechanistically well-understood chemical entities. The latest generation of alkyne metathesis catalysts combines excellent activity with outstanding chemoselectivity and functional group tolerance. The most noticeable catalysts in this regard are molybdenum alkylidynes endowed with triarylsilanolates as ancillary ligands, which can be readily prepared on multigram scale. These complexes are rendered bench-stable by complexation with 1,10-phenanthroline or 2,2′-bipyridine and are hence easy to work with. This chapter summarizes the evolution of the field from the very beginnings to its current mature state. To this end, a brief overview over the organometallic background is presented, followed by a detailed discussion of the preparative significance of alkyne metathesis in general. A host of comparative data allows the different catalysts available to the practitioner to be properly assessed, whereas selected applications to material science and natural product synthesis showcase the remarkable scope, performance, and reliability of this transformation even in very challenging settings