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Asymmetric arylation of aldimines catalyzed by heterogeneous chiral rhodium nanoparticles has been developed. The reaction proceeded in aqueous media without significant decomposition of the imines by hydrolysis to afford chiral (diarylmethyl)amines in high yields with outstanding enantioselectivities. This catalyst system exhibited the highest turnover number (700) in heterogeneous catalysts reported to date for these reactions. The reusability of the catalyst was also demonstrated.

Heterogeneous catalysts for fine chemical synthesis play a crucial role in establishing an efficient chemical process. Immobilization of homogeneous catalysts is an important method for the preparation of heterogeneous catalysts; however, it is often accompanied by a loss of catalytic activity due to limited mass transport in the support matrix. Here, we have designed core/shell type polystyrene shell supports on silica with low degrees of cross-linking to improve accessibility to reaction sites. It was found that rhodium–chiral diene complexes on core/shell particles showed higher catalytic activity in comparison those on conventional supports and even better catalytic activity than the corresponding homogeneous catalyst in asymmetric 1,4-addition reactions. Our results may provide a general strategy to obtain many other heterogeneous catalysts with high activities.

A ligand library containing 31 chiral diamines was synthesized using a flow-based semiautomatic reductive amination system. These ligands were evaluated in a continuous-flow asymmetric 1,4-addition reaction with a heterogeneous Ni catalyst. Based on the experimental results of ab initio DFT calculations, a prediction model for enantioselectivities was successfully constructed. Furthermore, virtual screening of possible ligands was conducted to identify promising structures, which showed good enantioselectivities in experiments.

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