Switchable Catalysts Used To Control Suzuki Cross-Coupling and Aza–Michael Addition/Asymmetric Transfer Hydrogenation Cascade Reactions

The development of a switchable strategy to control the catalytic action of dual active species is of great significance toward the precise manipulation of a cascade reaction. Herein, by combining water-soluble thermoresponsive polymer and hollow-shell-structured mesoporous silica as an integrated support, we develop a form of switchable-type supported molecule catalysts by tethering the achiral organic functionality in the outer polymer coating layers and anchoring the chiral ruthenium/diamine functionality in the inner mesoporous silica's nanochannels. As presented in this study, the created on and off modes of water-soluble thermoresponsive polymer coating layers on the external surface of silica shell can open and close the entrances of the nanochannels, thereby selectively initiating or terminating the catalytic action of the chiral ruthenium/diamine species within the nanochannels. As we envisaged, the switchable bifunctional catalysts are able to manipulate catalytic cascade sequences for the Suzuki cross-coupling/asymmetric transfer hydrogenation of iodoacetophenones and aryl boronic acid, and the aza–Michael addition/asymmetric transfer hydrogenation of enones and arylamines.