In an enantioselective reaction, we expect to obtain two types of chiral products through a controllable strategy in asymmetric catalysis. Herein, we develop Ru-catalysed asymmetric transfer hydrogenation of α-ketoimides to realise an enantioselective construction of chiral α-hydroxy imides or chiral α-hydroxy esters. The transformation of α-ketoimides catalysed by (S,S)-[RuCl(η⁶-mesitylene)diamine] can afford various chiral α-hydroxy imides with high yields and enantioselectivities, whereas that catalysed by (S,S)-[RuCl(η⁶-hexamethylbenzene)diamine] gives the desirable chiral α-hydroxy esters through a slight adjustment of the reaction conditions. The method described here is a controllable organic transformation with sodium formate as a hydrogen source under mild reaction conditions, and the benefit of this transformation is that various chiral α-hydroxy imides or α-hydroxy esters can be obtained selectively from α-ketoimides.

A cinchona alkaloid-functionalized heterogeneous catalyst is prepared through a thiol-ene click reaction of chiral N-(3,5-ditrifluoromethylbenzyl)quininium bromide and a mesostructured silica, which is obtained by co-condensation of 1,2-bis(triethoxysilyl)ethane and 3-(triethoxysilyl)propane-1-thiol. Structural analyses and characterizations disclose its well-defined chiral single-site active center, and electron microscopy images reveal its monodisperse property. As a heterogenous catalyst, it enables an efficient asymmetric epoxidation of achiral β-trifluoromethyl-β,β-disubstituted enones, the obtained chiral products can then be converted easily into enriched chiral β-trifluoromethyl-β-hydroxy ketones through a sequential epoxidation-relay reduction process. Furthermore, such a heterogeneous catalyst can be recovered conveniently and reused in asymmetric epoxidation of 4,4,4-trifluoro-1,3-diphenylbut-2-enone, showing an attractive feature in a practical construction of enriched chiral β-CF₃-substituted molecules.

An important challenge in asymmetric cascade reactions is solving the intrinsic incompatibility of two types of distinct organometallic complexes that participate in a one-pot reaction. Herein, we develop an organoruthenium-/organopalladium-bifunctionalized periodic mesoporous organosilica and realize one-pot cascade reactions of Ru-catalyzed asymmetric transfer hydrogenation and Pd-relay-catalyzed cross-coupling of haloacetophenones and arylboronic acids to various chiral biaryl alcohols, with quantitative conversions and up to 98 % enantioselectivity in an aqueous medium. This characteristics is attributed to the site-isolated, uniformly distributed, well-defined single-site palladium and ruthenium active species. Furthermore, the heterogeneous catalyst is conveniently recovered and reused repeatedly for eight times without loss of its catalytic activity, showing particular attractiveness for practicing organic transformation.

Phenylene-coated organorhodium-functionalized magnetic nanoparticles are developed through co-condensation of chiral 4-(trimethoxysilyl)ethyl)phenylsulfonyl-1,2-diphenylethylene-diamine and 1,4-bis(triethyoxysilyl)benzene onto Fe₃O₄ followed complexation with [{Cp*RhCl₂}₂]. This magnetic catalyst exhibits excellent catalytic activity and high enantioselectivity in asymmetric transfer hydrogenation in aqueous medium. Such activity is attributed to the high hydrophobicity and the confined nature of the chiral organorhodium catalyst. The magnetic catalyst can be easily recovered by using a small external magnet and it can be reused for at least 10 times without loss of its catalytic activity. This characteristic makes it an attractive catalyst for environmentally friendly organic syntheses.

Chiral organorhodium-functionalized hollow-shell-structured nanospheres were prepared by immobilization of a chiral N-sulfonylated diamine-based organorhodium complex within an ethylene-bridged organosilicate shell. Structural analysis and characterization reveal its well-defined single-site rhodium active center, and transmission electron microscopy images reveal a uniform dispersion of hollow-shell-structured nanospheres. As a heterogenous catalyst, it exhibits excellent catalytic activity and enantioselectivity in synthesis of chiral phthalides by a tandem reduction/lactonization of ethyl 2-acylarylcarboxylates in aqueous medium. The high catalytic performance is attributed to the synergistic effect of the high hydrophobicity and the confined chiral organorhodium catalytic nature. The organorhodium-functionalized nanospheres could be conveniently recovered and reused at least 10 times without loss of catalytic activity. This feature makes it an attractive catalyst in environmentally friendly organic reactions. The results of this study offer a new approach to immobilize chiral organometal functionalities within the hollow-shell-structured nanospheres to prepare materials with high activity in heterogeneous asymmetric catalysis.

Phase-transfer featured, imidazolium-based, organic-inorganic hybrid silica represents a novel functionalized platform with particularly attractive features in asymmetric catalysis. Herein, we report a chiral organorhodium-functionalized heterogeneous catalyst. As demonstrated in the studies, it displays comparable or higher catalytic activity and enantioselectivity than its homogeneous counterpart in asymmetric transformations. The superior catalytic performance is attributed to the synergistic effect of the salient imidazolium phase-transfer character and the confined chiral organorhodium catalytic nature in addition to the merits of mesoporous silica. Furthermore, it is more robust than other silica-derived heterogeneous systems and can be conveniently recovered and reused at least 10 times without loss of its catalytic efficiency. These features render the catalyst particularly attractive in practice of organic synthesis. The outcomes from the study clearly show that the strategy described here offers a general approach to immobilization of chiral ligand-derived silane onto the phase-transfer featured imidazolium-based organic-inorganic hybrid silica materials with significant improving catalyst efficiency.

A chiral diamine-based homogeneous cationic rhodium catalyst was developed and two heterogeneous cationic rhodium catalysts were obtained via the encapsulation of the homogeneous cationic rhodium catalyst within Me-SBA-15 and Me-SBA-16. All these catalysts presented excellent catalytic activities and high enantioselectivities in ultrasound-promoted asymmetric transfer hydrogenation of aromatic ketones and represent a successful use of the ion-pair immobilization strategy. More importantly, the encapsulation of the cationic rhodium functionality within Me-SBA-16 had an obvious high recyclability, in which the recycled catalyst could be reused nine times without significantly affecting its enantioselectivity, showing good potential in industrial application.

A periodic mesoporous organosilica (PMO) with chiral cyclohexyldiamine-based nickel(II) complexes incorporated within the silica framework was prepared through a co-condensation of (1R,2R)-cyclohexyldiamine-derived silane and Ph-bridged silane followed by complexation of nickel(II) bromide in the presence of (1R,2R)-N,N′-dibenzylcyclohexyldiamine. Structural analyses by X-ray powder diffraction, nitrogen sorption and transmission electron microscopy disclosed its orderly mesostructure while characterization by solid-state NMR and X-ray photoelectron spectroscopy demonstrated the well-defined single-site chiral bis(cyclohexyldiamine)-based nickel(II) active centers incorporated within the PMO material. In particular, as a heterogeneous chiral catalyst, this periodic mesoporous organosilica showed high catalytic activity and excellent enantioselectivity in asymmetric Michael addition of 1,3-dicarbonyl compounds to nitroalkenes (more than 92% conversions and up to 99% ee values). More importantly, this heterogeneous catalyst could be recovered easily and reused repeatedly nine times without obviously affecting its ee value, showing good potential for industrial applications.

A functionalized periodic mesoporous organosilica with incorporated chiral bis(cyclohexyldiamine)-based Ni^II complexes within the silica framework was developed by the co-condensation of (1R,2R)-cyclohexyldiamine-derived silane and ethylene-bridge silane, followed by the complexation of NiBr₂ in the presence of (1R,2R)-N,N′-dibenzylcyclohexyldiamine. Structural characterization by XRD, nitrogen sorption, and TEM disclosed its orderly mesostructure, and FTIR and solid-state NMR spectroscopy demonstrated the incorporation of well-defined single-site bis(cyclohexyldiamine)-based Ni^II active centers within periodic mesoporous organosilica. As a chiral heterogeneous catalyst, this functionalized periodic mesoporous organosilica showed high catalytic activity and excellent enantioselectivity in the asymmetric Michael addition of 1,3-dicarbonyl compounds to nitroalkenes, comparable to those with homogeneous catalysts. In particular, this heterogeneous catalyst could be recovered easily and reused repeatedly up to nine times without obviously affecting its enantioselectivity, thus showing good potential for industrial applications.

Two magnetic chiral iridium and rhodium catalysts were prepared via directly postgrafting 1,2-diphenylethylenediamine-derived organic silica or 1,2-cyclohexanediamine-derived organic silica onto the silica-coated iron oxide nanoparticles followed by complexation with iridium(III) or rhodium(III) complexes. During the asymmetric transfer hydrogenation of aromatic ketones in aqueous medium, the magnetic chiral catalysts exhibited high catalytic activities (up to 99% conversion) and enantioselectivities (up to 92% ee). Both catalysts could be recovered easily by magnetic separation and be reused ten times without significantly affecting their catalytic activities and enantioselectivities.

A mesoporous, silica-supported, chiral iridium catalyst with a highly ordered dimensional-hexagonal mesostructure was prepared by postgrafting the organometallic complex (1-diphenylphosphino-2-triethylsilylethane)[(R,R)-1,2-diphenylethylenediamine]iridium chloride {IrCl[PPh₂(CH₂)₂Si(OEt)₃]₂[(R,R)-DPEN] (DPEN=1,2-diphenylethylenediamine)} on SBA-15 silica. During the asymmetric hydrogenation of various aromatic ketones under 40 atm of hydrogen, the mesoporous, silica-supported, chiral iridium catalyst exhibited high catalytic activity (more than 95% conversions) and excellent enantioselectivity (up to more than 99% ee). The catalyst could be recovered easily and used repetitively seven times without significantly affecting the catalytic activity and the enantioselectivity.