Enantioselective Nickel-Catalyzed Si–C(sp2) Bond Activation and Migratory Insertion to Aldehydes: Reaction Scope and Mechanism

Copper-Catalyzed Asymmetric Synthesis of Silicon-Stereogenic Benzoxasiloles

A Cu-catalyzed asymmetric synthesis of silicon-stereogenic benzoxasiloles has been realized via intramolecular Si-O coupling of [2-(hydroxymethyl)phenyl]silanes. Cu(I)/difluorphos is found to be an efficient catalytic system for enantioselective Si-C bond cleavage and Si-O bond formation. In addition, kinetic resolution of racemic substituted [2-(hydroxymethyl)phenyl]silanes using Cu(I)/ PyrOx (pyridine-oxazoline ligands) as the catalytic system is developed to afford carbon- and silicon-stereogenic benzoxasiloles. Ring-opening reactions of chiral benzoxasiloles with organolithiums and Grignard reagents yield various enantioenriched functionalized tetraorganosilanes.

Rhodium-Catalyzed Addition of (Trialkylsilyl)arenes to Electrophiles via π-Coordination-Driven C-Si Bond Activation

Aromatic organosilicon compounds serve as valuable synthons due to their diverse reactivities, excellent compatibility with various functional groups, and ready availability. However, (trialkylsilyl)arenes, despite their potential utility, are generally considered unsuitable substrates for transition-metal-catalyzed cross-coupling due to the low polarity of their covalent C(aryl)-Si bonds and the significant steric hindrance imposed by alkyl substituents. These factors render them inert toward reactions with transition metals, such as transmetalation and oxidative addition. In this study, we present a method for the rhodium-catalyzed addition of (trialkylsilyl)arenes to electrophiles via π-coordination-driven desilylation. We propose that a dicationic rhodium species activates the unbiased C(aryl)-Si bond, increasing its polarity by forming an η6-arene complex, thereby facilitating heterolysis. The resulting phenyl anion complex readily engages in addition reactions with external electrophiles, effectively forming C-C bonds. Through comprehensive computational studies, we have unraveled an unexpected stepwise pathway for desilylation with fluoride. This pathway involves the addition of fluoride to the aromatic ring, followed by a 1,2-migration of fluoride, ultimately culminating in the departure of fluorotrimethylsilane.

Rhodium-Catalyzed Hydrolytic Cleavage of the Silicon-Carbon Bond of Silacyclobutanes to Access Silanols

Herein, we report the first rhodium-catalyzed hydrolytic cleavage of the silicon-carbon bond in silacyclobutanes using water as the reactant. A series of silacyclobutanes could be employed in this reaction in the presence of the Rh/BINAP complex, resulting in the corresponding silanols in good yields. Additionally, a chiral 1,1,4,4-tetraaryl-2,3-O-isopropylidene-l-threitol-derived phosphoramidite ligand could be used in this reaction to yield Si-stereogenic silanol with promising enantioselectivity.

Catalytic Asymmetric Dehydrogenative Si-H/N-H Coupling: Synthesis of Silicon-Stereogenic Silazanes

Despite growing progress in the construction of silazanes, the catalytic asymmetric synthesis of silicon-stereogenic silazanes is significantly less explored and remains a considerable challenge. Herein, we report a highly enantioselective synthesis of silicon-stereogenic silazanes via catalytic dehydrogenative coupling of dihydrosilanes with anilines. The reaction readily produces a wide range of chiral silazanes and bis-silazanes in excellent yields and stereoselectivities (up to 99% ee). Further utility of this process is demonstrated by the construction of polycarbosilazanes featuring configurational main chain silicon-stereogenic chirality. In addition, the straightforward transformation of the enantioenriched silazanes delivers various chiral silane compounds in a stereospecific fashion, illustrating their potential utilities as synthons for the synthesis of novel silicon-containing functional molecules.

An unusual autocatalysis with an air-stable Pd complex to promote enantioselective synthesis of Si-stereogenic enynes

Given the powerful potential of chiral-at-silicon chemistry, enantioselective synthesis of Si-stereogenic centers has attracted substantial research interest in recent years. However, the catalytic asymmetric synthesis of Si-stereogenic organosilicon compounds remains an appealing venture and is a challenging subject because of the difficulty in achieving high reactivity and stereoselectivity for "silicon-center" transformations. Herein, we disclose a highly enantioselective palladium-catalyzed hydrosilylation of 1,3-diynes with dihydrosilanes, which enables the facile preparation of Si-stereogenic enynes and an enyne-linked chiral polymer (polyenyne) in good yields and excellent ees (up to >99%) by desymmetrization. The unusual stereoselectivity in this reaction is achieved by precisely controlling the steric hindrance and electronic effect of the newly developed chiral ligands, resulting in a wide range of chiral silanes and a Si-containing polymer bearing a Si-stereogenic center which is otherwise difficult to access. The key to the high enantioselectivity relies on catalyst aggregation-induced non-covalent interaction, which exerts a remarkably positive influence on the Si-H bond activation and enhancement of enantioselectivity, in which the palladium/P-ligand complex was proved to be air-stable and moisture-insensitive in this reaction.

Recent advance in the reactions of silacyclobutanes and their applications

Silacyclobutanes (SCBs), as a key member of organosilicon family, have received considerable attention in synthetic chemistry since the silicon-carbon bond can be activated. Followed by ring-opening and ring expansion process,...