Notably, the alkynyl group on the chiral N-propargyl indoles prodvided a useful and versatile handle for derivatizations (Figure ). For exmple, desilylation of 6a provided the enantioenriched terminal alkyne 8, which subsequently underwent the Sonogashira coupling to afford the aryl-substituted alkynye product 9. Terminal alkyne 8 underwent a click reaction to give chiral triazole 10. Reduction of 8 with Lindar Pd and H 2 afforaded chiral N-allylic indole 11, while reduction of 6a with DIBAL-H produced chiral vinylsilyl compound 12. Mechanistic studies. To gain insight into the mechanism and origin of selectivity, a series of experiments well conducted. Generally, the hydrocarbonation process consists of π-bond insertion into L*Ni-H species, oxidative addition of the resulting L*Ni-alkyl intermediate, and reductive elimination to form product and the L*Ni-H catalyst. Take the hydroarylation as an example, competition experiments were performed to compare the reactivity between different aryl halides, indicating that i) electron-deficent aryl bromide is more reactive than an electronrich one (Figure ), and ii) aryl bromide is more reactive than aryl iodide (Figure -ii). In fact, a competing reductive hydrodehalogenation event was observed when an aryl iodide was uesd as the electrophile (Figure -iii), suggesting it is disadvantaged for the final product formation that oxidative addition of L*Ni complex prior to generation of L*Ni-alkyl intermediate. Next, the hydroarylation of 1a was chosen for kinetic studies, and the reaction progress was monitored by F and 1 H NMR. Initial rate experiments disclosed that the reaction was zero-order in N-alkenyl indole, first-order in catalyst and aryl bromide, and fractional-order in diethoxymethylsilane (Figure , see the Supplementary Information for details). Moreover, Hammett studies were also performed to evaluate the influence that electronic variation of the aryl electrophiles had on the rate of hydroarylation (Figure ). As a result, a variety of parasubstituted aryl bromides reacted with N-vinylindole 1a at different rates, indicating that electronic variation of the aryl electrophile had a remarkable impact on the rate of N-vinylindole hydroarylation. A linear relationship was further observed through a Hammett plot. The positive slope (ρ = 0.67) suggests negative charge accumulation in the rate-determining transition state, which is stabilized by electron-withdrawing substituents. Taken together, the above results reveal that oxidative addition is most likely the turnover-limiting step. Furthermore, a linear correlation was observed by nonlinear effect studies on the enantiomeric composition of chiral ligand L*1 and N-alkylindole product 3o (Figure ), which is consistent with a ligated nickel catalyst being of a monomeric nature. To identify the enantiodetermining step of the N-vinylindole hydroarylation reaction, we next investigated linear free energy relationships (LFERs) between the Hammett electronic parameters of various parasubstituted aryl bromides and the enantioselectivities of the corresponding products (Figure ). 24 A linear correlation was observed with para-substituted aryl bromides as enantioselectivity increased with the introduction of electron-withdrawing groups (ρ = 1.07): 56% ee and 92% ee were observed for 4-methoxyphenyl bromide (σ = -0.27) and 4-acetylphenyl bromide (σ = 0.50), respectively, implying that the enantioselectivity of the process is not solely under catalyst control. In addition, the silane did essentially not affect the enantioselectivity of the reaction. On the basis of these results, oxidative addition is most likely the enantiodetermining step.