Cobalt-catalyzed asymmetric hydrogenation of enamides enabled by single-electron reduction

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Science  25 May 2018:
Vol. 360, Issue 6391, pp. 888-893
DOI: 10.1126/science.aar6117

Reduction can make cobalt act precious

Enzymes rely on abundant metals such as iron and nickel to manipulate hydrogen. Chemists, on the other hand, have largely had to rely on precious metals such as platinum and rhodium for the task. Friedfeld et al. now report a simple trick to make cobalt act more like rhodium. Reduction of Co(II) to Co(I) by zinc reinforced binding of phosphine ligands to the metal to facilitate its use in asymmetric hydrogenation of alkenes. The cobalt catalysts tolerated alcohol solvents, unlike their rhodium congeners, and could be applied to a 200-gram-scale reduction at 0.08% loading.

Science, this issue p. 888