Progress in the trans-Reduction and trans-Hydrometalation of Internal Alkynes. Applications to Natural Product Synthesis

The classical repertoire of synthetic organic chemistry is short of methods that allow triple bonds to be transformed into (E)-alkenes with high selectivity in the presence of other reducible sites. Recent advances, most notably in ruthenium catalyzed trans-hydrogenation, trans-hydrosilylation, transhydrogermylation, trans-hydrostannation, and even transhydroboration hold the promise of filling this gap. This review illustrates the state-of-the-art in the field by summarizing applications of these emerging methodologies to natural product synthesis. A comparison of ruthenium-catalyzed and radical induced trans-hydrostannations provides further insights into the application profile of these transformations.