Highly recoverable organoruthenium-functionalized mesoporous silica boosts aqueous asymmetric transfer hydrogenation reaction

Exploring functionalized mesoporous silica to achieve enhanced catalytic activity and enantioselectivity in heterogeneous asymmetric catalysis presents a significant challenge that is critical for understanding the function of support and controlling chiral complexation behavior. In this contribution, by cooperative assembly of chiral 4-(trimethoxysilyl)ethyl)phenylsulfonyl-1,2-diphenylethylene-diamine and tetraethoxysilane followed by complexation with organoruthenium complex, we report a unique three-dimensional chiral organoruthenium-functionalized chrysanthemum-like mesoporous silica (CMS). As demonstrated in the studies, taking advantage of the active site-isolated chiral organoruthenium catalytic nature, this heterogeneous catalyst ArRuTsDPEN-CMS (Ar = hexamethylbenzene, TsDPEN = 4-methylphenylsulfonyl-1,2-diphenylethylene-diamine) displays enhanced catalytic activity and enantioselectivity in aqueous asymmetric transfer hydrogenation with extensive substrates. Furthermore, this heterogeneous catalyst can be conveniently recovered and reused at least 10 times without loss of its catalytic efficiency. These features render this catalyst particularly attractive in practice of organic synthesis in an environmentally friendly manner. Also, this outcome from the study clearly shows that the strategy described here offers a general approach to immobilization of chiral ligand-derived silane onto a functionalized mesoporous material with significant improving catalytic activity.