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• Density functional theoretical (DFT) calculations were performed to reveal the mechanism for nickel-catalyzed hydroaminomethylation reaction of alkyne with imine. • An alternative Ni(I) mechanism, without a redox reaction, was proposed by DFT calculations. The mechanism based on these calculations is favorable compared with the previously proposed redox Ni(0)-Ni(II) pathway. • AIM analysis shows that the dissociation of the amine ligand to provide a vacancy would lead to a higher free-energy barrier for the Ni(0)-Ni(II) pathway. Herein, we report a theoretical investigation on the nickel-catalyzed hydroaminomethylation reaction of alkyne with imine. In this work, an alternative Ni(I) mechanism, without a redox reaction, was proposed by DFT calculations. The mechanism based on these calculations is favorable compared with the previously proposed redox Ni(0)-Ni(II) pathway. A Ni(I)-amino complex is considered to be the active species, which can be obtained from hydrogen transfer between an imine-coordinated Ni(0) complex and an amine. A Meerwein-Ponndorf type hydride transfer takes place between an amino group and a coordinated alkyne. Then an imine insertion affords Ni(I)-allylamino. Proton transfer with the approaching imine yields the hydroaminomethylation product and regenerates the Ni(I)-amino active species. Throughout the catalytic cycle, the oxidative state of Ni remains at +1. Furthermore, AIM analysis shows that the dissociation of the amine ligand to provide a vacancy would lead to a higher free-energy barrier for the Ni(0)-Ni(II) pathway. An alternative Ni(I) mechanism, without a redox reaction, was proposed by DFT calculations. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The mechanism and origin of selectivities of NHC-catalyzed hydroacylation-Stetter reaction has been systematically studied. • The role of NHC has been disclosed by using global reactivity index analysis. • ELF and IRC analyses are performed to clarify the bonding modes of hydroacylation and Stetter reaction. The regioselectivity of hydroacylation mediated by transition metal and organocatalyst has been and continues to be one of the most challenging questions in the synthesis field. To explore the possible mechanisms and origin of the regio-/enantioselectivity, the density functional theory (DFT) calculations were performed for studying intramolecular hydroacylation-Stetter reaction of alkynyl bisbenzaldehyde catalyzed by N-heterocyclic carbene (NHC). Computational results show that the hydroacylation process was the rate-determining step and irreversible. Four different stereoisomers (RR, RS, SR, and SS) were considered and the lowest energy mode agreed with the reported enantioselectivity in experiment. Global reaction index (GRI) analysis showed that NHC catalyst can convert alkynyl bisbenzaldehyde electrophilic carbonyl carbon into nucleophilicity to initiate the reaction. Moreover, electron localization function (ELF) and intrinsic reaction coordinate (IRC) analyses were performed to characterize the manner difference between the process of hydroacylation and Stetter reaction. [ABSTRACT FROM AUTHOR]