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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