Scientists have developed a method for cross and branched selective hydroalkenylation of alkenes by selecting a metal hydride.[1] This reaction uses a cobalt hydride catalyst for the enantioselective hydroalkenylation of alkenes with potassium organotrifluoroborates.[1] The process takes place via the MHAT (metal hydride hydrogen atom transfer) mechanism and radical-polar crossover, which begins with the formation of cationic cobalt(III) and Co(III)–F complexes, followed by transmetalation.[1] The method produces a series of α-chiral alkenes in good yields, excellent regio- and enantioselectivity and good functional group compatibility.[1] Alkenyl nucleophiles with electron-donating or -withdrawing groups in the para- and meta-positions of phenyl provide chiral products with high efficiency.[1] The O-methyl group in the ortho-position of the aryl reduces the enantioselectivity.[1] The reaction serves as a new efficient way to synthesize valuable α-chiral olefins using nucleophilic alkenyl reagents.[1]