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

Classical metalation reactions such as the metal-halogen exchange have had a transformative impact on organic synthesis owing to their broad applicability in building carbon-carbon bonds from carbon-halogen bonds. Extending the metal-halogen exchange logic to a metal-carbon exchange would enable the direct modification of carbon frameworks with new implications in retrosynthetic analysis. However, such a transformation requires the selective cleavage of highly inert chemical bonds and formation of stable intermediates amenable to further synthetic elaborations, hence its development has remained considerably challenging. Here we introduce a skeletal metalation strategy that allows lactams, a prevalent motif in bioactive molecules, to be readily converted into well-defined, synthetically useful organonickel reagents. The reaction features a selective activation of unstrained amide C–N bonds mediated by an easily prepared Ni(0) reagent, followed by CO deinsertion and dissociation under mild room temperature conditions in a formal carbonyl-to-nickel-exchange process. The underlying principles of this unique reactivity are rationalized by organometallic and computational studies. The skeletal metalation is further applied to a direct CO excision reaction and a carbon isotope exchange reaction of lactams, underscoring the broad potential of metal-carbon exchange logic in organic synthesis.