Cross- and branched-selective hydroalkenylation by metal hydride selection

Controlled placement of branch points along carbon chains is a core capability in the synthesis of materials, agrochemicals, and pharmaceuticals. Metal hydride hydrogen atom transfer (MHAT) to alkenes represents a valuable elementary step because it accesses branched products directly from abundant α-olefins. MHAT catalysis can also be coupled to secondary transition metal catalytic cycles that would otherwise deliver nonbranched (linear) products. However, the hydridic reagents used in MHAT do not always discriminate between the MHAT catalyst and the secondary metal, leading to mixtures of metal hydrides and, therefore, mixtures of products. In this work, we show that a combination of a lutidinium acid and manganese, a weak reductant, selectively generates cobalt hydrides in the presence of a nickel catalyst. We applied these conditions to a cross-selective alkene-alkene coupling that produces valuable branched materials with exquisite selectivity.