A series of conventional deuterium labelling experiments further improved our understanding of the detailed reaction mechanism. The migratory hydroalkylation of the alkene 1a was conducted under both method A and method B using Ph2SiD2 (Figure ). We observed the incorporation of deuterium at the γ and δ positions of the amide group, and no H/D exchange was observed at the α or β position of the amide group. The deuterium content at the δ position is always higher than that at the γ position, indicating that Markovnikov-(rather than anti-Markovnikov-) hydrometallation is favoured. No α-or β-deuterium atom was observed, thus excluding the possibility of nickel walking back and forth along the alkyl chain. Furthermore, β-located alkyl-nickel could participate in cross-coupling or migrate to the α position but could not migrate to the outer γ-position. A δ,δdideuterated alkene (δ,δ-d2-1a) was reacted with the alkyl halide 2a under method A and method B separately (Figure ). It is interesting to note that the deuterium content at the δ-position decreased slightly, and no H/D exchange was observed along the chain. This phenomenon indicated that the γ-located nickel prefers chain walking toward the amide group to from α-or β-located alkyl-nickel species. A β,β-dideuterated alkene (β,β-d2-1a) was reacted with alkyl halides 2k and 2H (Figure ). The β-and γ-position deuterated products d2-4ak and d2-5aH were obtained, respectively, and no deuteration was observed at the α position of the amide group. This conclusion was similar to that obtained from Figure ; nickel walking back and forth along the alkyl chain was less likely; in particular, α-located alkyl-nickel could not migrate to the outer β-or γ-position. We studied the stereochemistry of the asymmetric catalytic process using Ph2SiD2 to conduct deuterium-labelling experiments (Figure ). Under method C, 3a smoothly reacted with 2k to deliver the deuterated product d1-6ak using Ph2SiD2. Deuterium was incorporated exclusively at the γ-position of the amide substituent. Thus, in this case, anti-Markovnikov-hydrometallation was completely forbidden. We observed a highly matched Z/E ratio of the starting material alkene (3g) and diastereoselectivity of products (6gI and 6gI') using either optically pure ligand or racemic ligand. We suggested that irreversible syn-hydrometalation was the regio-and enantio-determining step. In total, we could conclude that nickel chain walking was not in a back-and-forth modality but in a unidirectional modality, i.e., toward the amide group and to form the α-or β-located alkyl-nickel species. Catalyst characterization and reaction kinetics. More information about the asymmetric catalytic process was obtained through catalyst characterization and reaction progress kinetic analysis. The enantiopurities of the ligands used and the obtained hydroalkylation products exhibited a linear relationship (Figure ). Therefore, a monomeric nickel complex and a single bisoxazoline ligand were involved in alkene hydrometalation as the enantio-determining step. In addition, the enantiomeric excess of the desired product would not be expected to change during the reaction process (Figure ). Reaction progress kinetic analysis (RPKA) of the model reaction (Figure , see Supplementary Figures for more details) was conducted. Different initial concentrations of alkene 1a, alkyl iodide 2b and hydrosilane (EtO)3SiH could barely affect the reaction rate under both method A and method B conditions, indicating zero-order kinetics. We employed the Burés graphical rate analysis to compare the relationship of the reaction rate and catalyst concentration. The alkene migratory hydroalkylation has a rate order of 0.58 for nickel catalyst under method A conditions, while has a rate order of 1.05 for nickel catalyst under method B conditions (see Supplementary Figures 6 & 14 for more details). These observations indicated that both the oxidation addition of alkyl iodide and the hydrometallation were nonrate-determining steps. →IN10→TS8→IN11 made it an irreversible step. This result was consistent with the outcomes in Figure that α-located alkyl-nickel could not migrate to the outer β-or γ-position. In total, the thermodynamic stability of IN12 over IN8 was responsible for the α-selective hydroalkylation, while the kinetics advantage of IN8→TS6 over IN8→TS7 was responsible for the β-selective hydroalkylation. In addition, the computational results reasonably explained our conclusion in Figure that the chain walking of nickel was not in a back-and-forth modality but in a unidirectional modality, i.e., toward the amide group and to form the α-or β-located alkyl-nickel species.