Rhodium-Catalyzed Dynamic Kinetic Asymmetric Hydrosilylation to Access Silicon-Stereogenic Center.

Strategies on the construction of enantiomerically pure silicon-stereogenic silanes generally relies on desymmetrization of prochiral and symmetric substrates. However, dynamic kinetic asymmetric transformations of organosilicon compounds have remained underdeveloped and unforeseen owing to a lack of an effective method for deracemization of the static silicon stereocenters. Here we report the first Rh-catalyzed dynamic kinetic asymmetric intramolecular hydrosilylation (DyKAH) with "silicon-centered" racemic hydrosilanes that enables the facile preparation of silicon-stereogenic benzosiloles in good yields and excellent enantioselectivities. The special rhodium catalyst controlled by non-diastereopure-type mixed phosphine-phosphoramidite ligand with axial chirality and multiple stereocenters can induce enantioselectivity efficiently in this novel DyKAH reaction. Density functional theory (DFT) calculations suggest that the amide moiety in chiral ligand plays important role in facilitating the SN 2 substitution of chloride ion to realize the chiral inversion of silicon center.

Long-Distance Chirality Transfer from P-Ligand to Prochiral Dihydrosilanes via Pd(II) Aryl Iodide Complex in Pd-Catalyzed Silylation of Aryl Iodide: A DFT Study.

The mechanism of Pd-catalyzed desymmetric monoarylation of dihydrosilanes with aryl iodides in the presence of chiral TADDOL-derived phosphoramidite ligand toward deeper understanding of the stereoselectivity has been investigated using hybrid density functional theory (DFT) methodology. The full catalytic cycle for the favorable reaction pathway, which is initiated by the oxidative addition of aryl iodide to monoligated Pd0 leading to the silylation product, was calculated. The DFT calculation results indicate that the enantio-discriminating transmetalation between Pd-Ar bond of the Pd(II) aryl iodide complex and Si-H bond of the prochiral dihydrosilane was the enantioselectivity-determining step. On the basis of the structure of the transition state, the attractive aryl-aryl interactions between the aryl group of ligand, aryl iodide, and dihydrosilane were found to play an important role for the chiral transference from the chiral ligand to asymmetric cleavage of the Si-H bond of the prochiral dihydrosilane.

Catalytic asymmetric oxidative carbonylation-induced kinetic resolution of sterically hindered benzylamines to chiral isoindolinones.

A highly enantioselective kinetic resolution of sterically hindered benzylamines has been achieved for the first time through transition-metal-catalyzed oxidative carbonylation, in which the new KR strategy offered a new approach to afford chiral isoindolinones (er up to 97 : 3) and the origin of chemoselectivity and stereoselectivity was confirmed by density functional theory (DFT) calculations.

Catalytic Asymmetric trans-Selective Hydrosilylation of Bisalkynes to Access AIE and CPL-Active Silicon-Stereogenic Benzosiloles.

Chirality widely exists in a diverse array of biologically active molecules and life forms, and the catalytic constructions of chiral molecules have triggered a heightened interest in the fields of chemistry and materials and pharmaceutical sciences. However, the synthesis of silicon-stereogenic organosilicon compounds is generally recognized as a much more difficult task than that of carbon-stereogenic centers because of no abundant organosilicon-based chiral sources in nature. Herein, we reported a highly enantioselective rhodium-catalyzed trans-selective hydrosilylation of silicon-tethered bisalkynes to access chiral benzosiloles bearing a silicon-stereogenic center. This protocol featured with chiral Ar-BINMOL-Phos bearing hydrogen-bond donors as a privileged P-ligand for catalytic asymmetric hydrosilylation that is operationally simple and has 100% atom-economy with good functional group tolerability as well as high enantioselectivity (up to >99:1 er). Benefiting from the trans-selective hydrosilylation with the aid of Rh/Ar-BINMOL-Phos-based asymmetric catalysis, the Si-stereogenic benzosiloles exhibited pronounced aggregation-induced emission (AIE) and circularly polarized luminescence (CPL) activity.

Tertiary amine-directed and involved carbonylative cyclizations through Pd/Cu-cocatalyzed multiple C-X (X = H or N) bond cleavage.

A novel Pd/Cu-cocatalyzed carbonylative cyclization by C-H activation and N-dealkylative C-N bond activation has been developed for the chemoselective construction of synthetically useful heterocycles. The N,N-dimethylamine group on o-indolyl-N,N-dimethylarylamines was found to act as both the directing group and reactive component in this C-H carbonylative cyclization reaction. Furthermore, a unique C-H oxidation/carbonylative lactonization of diarylmethylamines is firstly demonstrated under modified reaction conditions, which could be easily applicable to the one-step synthesis of multi-substituted phthalides bearing an N,O-ketal skeleton that is difficult to access by previously reported methods. Mechanistic studies implicate that Pd/Cu-cocatalyzed C-H oxidation/carbonylative lactonization is a sequential reaction system via Cu-catalyzed C(sp3)-H oxidation and Pd-catalyzed oxidative carbonylation of the C(sp2)-H bond. It was found that trace amounts of water are essential to promote the Cu-catalyzed C(sp3)-H oxidation of diarylmethylamine for the formation of the hydroxyl group, which could act as an in situ-formed directing group in the intramolecular carbonylative lactonization step.