Selectivity Enhancement in Dynamic Kinetic Resolution of Secondary Alcohols through Adjusting the Micro-Environment of Metal Complex Confined in Nanochannels: A Promising Strategy for Tandem Reactions

Dichloro­(η⁶-<i>p</i>-cymene) (1-butyl-3-cyclohexyl-imidazolin-2-ylidene) ruthenium­(II) (<b>RuL</b>) was synthesized and confirmed. Five heterogeneous catalysts with similar ruthenium cores were prepared by chemical immobilization method using various silica-based supports, including mesoporous silica SBA-15 of different pore sizes (<b>Ru/Si-9</b>, <b>Ru/Si-8</b>, and <b>Ru/Si-7</b>), nonporous silica particles (<b>Ru/SiO</b>_<b>2</b>), and surface trimethylsilylated SBA-15 (<b>Ru/SiMe</b>). The dynamic kinetic resolution (DKR) of 1-phenylethanol, which includes metal–enzyme bicatalytic racemization in tandem with stereoselective acylation, gave product in 99% yield and 0% ee with homogeneous catalyst <b>RuL</b>, whereas the heterogeneous <b>Ru/Si-8</b> exhibited high catalytic activity and enantioselectivity (up to 96% yield and 99% ee). The racemization and acylation abilities of different catalysts were analyzed. The influences of pore size and surface properties for heterogeneous catalysts were investigated, and the nanocage effect was found to be the key factor in stereoselectivity. The catalyst <b>Ru/Si-8</b> performed well in reactions with various substrates and can be reused for at least seven times

An Interface-Directed Coassembly Approach To Synthesize Uniform Large-Pore Mesoporous Silica Spheres

A facile and controllable interface-directed coassembly (IDCA) approach is developed for the first time to synthesize uniform discrete mesoporous silica particles with a large pore size (ca. 8 nm) by using 3-dimensional macroporous carbon (3DOMC) as the nanoreactor for the confined coassembly of template molecules and silica source. By controlling the amount of the precursor solution and using Pluronic templates with different compositions, we can synthesize mesoporous silica particles with diverse morphologies (spheres, hollow spheres, and hemispheres) and different mesostructure (e.g., 2-D hexagonal and 3D face centered cubic symmetry), high surface area of about 790 m²/g, and large pore volume (0.98 cm³/g). The particle size can be tunable from submicrometer to micrometer regimes by changing the macropore diameter of 3DOMC. Importantly, this synthesis concept can be extended to fabricate multifunctional mesoporous composite spheres with a magnetic core and a mesoporous silica shell, large saturated magnetization (23.5 emu/g), and high surface area (280 m²/g). With the use of the magnetic mesoporous silica spheres as a magnetically recyclable absorbent, a fast and efficient removal of microcystin from water is achieved, and they can be recycled for 10 times without a significant decrease of removal efficiency for microcystin