Experimental analysis of Cl−Ni−SAC indicated the uniform distribution of Ni and Cl in the N-rich carbon support, which can have the advantage of homogenous catalyst and heterogenous catalyst. The obtained Cl−Ni−SAC mediated a fast and efficient ring-opening reaction of epoxides with high recyclability, thereby demonstrating its applicability to a continuous-flow reaction.
Nickel single-atom-catalysts (Ni−SACs), which are known for their unique catalytic activity, are mainly used in electrocatalytic reactions that focus on high metal loading in carbon support to improve their performance. However, we attempted to modify the Ni species to find new catalytic properties by hypothesizing that functionalized Ni−SACs can exhibit strong Lewis acidic properties in organic reactions. Herein, a low-temperature salt-assisted synthesis of highly Lewis acidic chlorine-bound nickel SAC (Cl−Ni−SAC) is established and the synthesized catalyst is applied to the ring-opening reaction of epoxides with alcohol. The obtained Cl−Ni−SAC facilitates a fast and efficient ring-opening reaction of epoxides with high recyclability. In addition, the highly active Cl−Ni−SAC was applied to the continuous flow set-up for sustainable transformation for 24 h, yielding 9.7 g of the desired product. Stereochemical experiments and density functional theory calculations demonstrated the importance of MeOH⋅⋅⋅Cl hydrogen bonding, N−H⋅⋅⋅Ni agostic interaction, and π-stacking in the transition state.Zum Volltext