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The stereodefined and highly substituted vinylsilanes are essential building blocks for constructing complex organic molecules. Transition metal‐mediated silylmetalation of alkynes was developed to overcome the limitations of conventional hydrosilylations; however, a very limited study was carried out to utilize transient vinylmetal species in cross‐coupling reactions. Moreover, they produce syn‐adduct, and the anti‐selective cross‐coupling is still unknown and highly desired. Silylzinc reagents are highly functional group tolerant, however, their synthesis from pyrophoric silyllithium and dissolved lithium salts hampers cross‐coupling reactions. Our novel solid silylzinc reagents circumvent these constraints are employed in the anti‐selective synthesis of vinylsilanes via a multi‐component reaction involving Me3SiZnI, terminal alkynes, and activated alkyl halides. An intensive computational and experimental investigation of the mechanism reveals an equilibrium between the intermediate syn‐ and anti‐adducts; the greater barrier at the single electron reduction of alkyl halides and the thermodynamic stability of the Ni(III) adduct determine the anti‐selectivity. [ABSTRACT FROM AUTHOR]

The nuanced role of spin effects remains a critical gap in designing proficient open‐shell catalysts. This study elucidates an iron‐catalyzed allylic C(sp3)−H silylation/alkyne hydrosilylation reaction, in which the spin state of the open‐shell iron catalyst dictates the reaction kinetics and pathway. Specifically, spin crossover led to alkyne hydrosilylation, whereas spin conservation resulted in a novel allylic C(sp3)−H silylation reaction. This chemoselectivity, governed by the spin‐crossover efficiency, reveals an unexpected dimension in spin effects and a first in the realm of transition‐metal‐catalyzed in situ silylation of allylic C(sp3)−H bonds, which had been previously inhibited by the heightened reactivity of alkenes in hydrosilylation reactions. Furthermore, this spin crossover can either accelerate or hinder the reaction at different stages within a single catalytic reaction, a phenomenon scarcely documented. Moreover, we identify a substrate‐assisted C−H activation mechanism, a departure from known ligand‐assisted processes, offering a fresh perspective on C−H activation strategies. [ABSTRACT FROM AUTHOR]

We report a highly enantioselective intermolecular C−H bond silylation catalyzed by a phosphoramidite‐ligated iridium catalyst. Under reagent‐controlled protocols, propargylsilanes resulting from C(sp3)−H functionalization, as well the regioisomeric and synthetically versatile allenylsilanes, could be obtained with excellent levels of enantioselectivity and good to excellent control of propargyl/allenyl selectivity. In the case of unsymmetrical dialkyl acetylenes, good to excellent selectivity for functionalization at the less‐hindered site was also observed. A variety of electrophilic silyl sources (R3SiOTf and R3SiNTf2), either commercial or in situ‐generated, were used as the silylation reagents, and a broad range of simple and functionalized alkynes, including aryl alkyl acetylenes, dialkyl acetylenes, 1,3‐enynes, and drug derivatives were successfully employed as substrates. Detailed mechanistic experiments and DFT calculations suggest that an η3‐propargyl/allenyl Ir intermediate is generated upon π‐complexation‐assisted deprotonation and undergoes outer‐sphere attack by the electrophilic silylating reagent to give propargylic silanes, with the latter step identified as the enantiodetermining step. [ABSTRACT FROM AUTHOR]

Enantioselective reactions that install functional groups at the positions of unactivated C-H bonds can be envisioned to produce intermediates for the synthesis of the active ingredients in pharmaceuticals and agrochemicals directly from simple feedstocks. Among these C-H bond functionalization reactions, those that form carbon-silicon (C-Si) and carbon-boron (C-B) bonds have been pursued because the products of these reactions can be converted to those containing a wide range of functional groups and because compounds containing silicon and boron possess unique properties that can be valuable for medicinal and materials chemistry. Although the silylation and borylation of C-H bonds have undergone extensive development during the past two decades, enantioselective versions of these reactions were not known until a few years ago. In this Minireview, we present the rapid development of enantioselective silylation and borylation of C-H bonds, with an emphasis on the design and development of the types of chiral ligands needed to achieve these reactions and an intention to inspire an expansion of these types of transformations.

Catalytic enantioselective intermolecular C−H silylation offers an efficient approach for the rapid construction of chiral organosilicon compounds, but remains a significant challenge. Herein, a new type of chiral silyl ligand is developed, which enables the first iridium‐catalyzed atroposelective intermolecular C−H silylation reaction of 2‐arylisoquinolines. This protocol features mild reaction conditions, high atom economy, and remarkable yield with excellent stereoselectivity (up to 99 % yield, 99 % ee), delivering enantioenriched axially chiral silane platform molecules with facile convertibility. Key to the success of this unprecedented transformation relies on a novel chiral PSiSi‐ligand, which facilitates the intermolecular C−H silylation process with perfect chem‐, regio‐ and stereo‐control via a multi‐coordinated silyl iridium complex. [ABSTRACT FROM AUTHOR]

Bent (hetero)allenes such as carbodicarbenes and carbodiphosphoranes can act as neutral C‐donor ligands, and diverse applications in coordination chemistry have been reported. N‐Heterocyclic diazoolefins are heterocumulenes, which can function in a similar fashion as L‐type ligands. Herein, we describe the synthesis and the reactivity of an anionic diazoolefin. This compound displays distinct reactivity compared to neutral diazoolefins, as evidenced by the preparation of diazo compounds via protonation, alkylation, or silylation. The anionic diazoolefin can be employed as an ambidentate, X‐type ligand in salt metathesis reactions with metal halide complexes. Extrusion of dinitrogen was observed in a reaction with PCl(NiPr2)2, resulting in a stable phosphinocarbene. [ABSTRACT FROM AUTHOR]

Benzylsilanes have found increasing applications in organic synthesis as bench‐stable synthetic intermediates, yet are mostly produced by stoichiometric procedures. Catalytic alternatives based on the atom‐economical silylation of benzylic C(sp3)−H bonds remain scarcely available as specialized directing groups and catalytic systems are needed to outcompete the kinetically‐favored silylation of C(sp2)−H bonds. Herein, we describe the first general and catalytic‐in‐metal undirected silylation of benzylic C(sp3)−H bonds under ambient, transition metal‐free conditions using stable tert‐butyl‐substituted silyldiazenes (tBu−N=N−SiR3) as silicon source. The high activity and selectivity of the catalytic system, exemplified by the preparation of various mono‐ or gem‐bis benzyl(di)silanes, originates from the facile generation of organopotassium reagents, including tert‐butylpotassium. [ABSTRACT FROM AUTHOR]

A desymmetrizing silylation of aromatic diols is reported. The previously unknown asymmetric silyl ether formation of phenol derivatives is achieved by applying List's counteranion directed silylation technique. A silylium‐ion‐like silicon electrophile generated from an allylic silane paired with an imidodiphosphorimidate (IDPi) enables enantioselective discrimination of achiral 1,1′‐biaryl‐2,6‐diols. The enantioselectivity of that desymmetrization is further improved by a downstream kinetic resolution, converting the monosilylated minor enantiomer into the corresponding, again achiral bissilylated diol. [ABSTRACT FROM AUTHOR]

The development of aryl alkyl sulfides as dichotomous electrophiles for site‐selective silylation via C−S bond cleavage has been achieved. Iron‐catalyzed selective cleavage of C(aryl)−S bonds can occur in the presence of β‐diketimine ligands, and the cleavage of C(alkyl)−S bonds can be achieved by t‐BuONa without the use of transition metals, resulting in the corresponding silylated products in moderate to excellent yields. Mechanistic studies suggest that Fe−Si species may undergo metathesis reactions during the cleavage of C(aryl)−S bonds, while silyl radicals are involved during the cleavage of C(alkyl)−S bonds. [ABSTRACT FROM AUTHOR]

The steric effects of substituents on five-membered rings are less pronounced than those on six-membered rings because of the difference in bond angles. Thus, the regioselectivities of reactions of five-membered heteroarenes that occur with selectivities dictated by steric effects, such as the borylation of C-H bonds, have been poor in many cases. We report that the silylation of five-membered-ring heteroarenes occurs with high sterically derived regioselectivity when catalyzed by the combination of [Ir(cod)(OMe)]2 (cod=1,5-cyclooctadiene) and a phenanthroline ligand or a new pyridyl-imidazoline ligand that further increases the regioselectivity. The silylation reactions with these catalysts produce high yields of heteroarylsilanes from functionalization at the most sterically accessible C-H bonds of these rings under conditions that the borylation of C-H bonds with previously reported catalysts formed mixtures of products or products that are unstable. The heteroarylsilane products undergo cross-coupling reactions and substitution reactions with ipso selectivity to generate heteroarenes that bear halogen, aryl, and perfluoroalkyl substituents.

Catalytic, three‐component, cross‐electrophile reactions have recently emerged as a promising tool for molecular diversification, but studies have focused mainly on the alkyl‐carbonations of alkenes. Herein, the scope of this method has been extended to conjugated dienes and silicon chemistry through silylative difunctionalization of 1,3‐dienes with chlorosilanes and aryl bromides. The reaction proceeds under mild conditions to afford 1,2‐linear‐silylated products, a selectivity that is different to those obtained from conventional methods via an intermediary of H(C)‐η3‐π‐allylmetal species. Preliminary mechanistic studies reveal that chlorosilane reacts with 1,3‐diene first and then couples with aryl bromide. [ABSTRACT FROM AUTHOR]

Optically active organosilanes have been demonstrated to be versatile chiral reagents in synthetic chemistry since the early seminal contributions by Sommer and Corriu. Among these silicon‐containing chiral architectures, monohydrosilanes, which bear a Si−H bond, hold a unique position because of their facile transformations through stereospecific Si–carbon or Si–heteroatom bond‐formation reactions. In addition, those compounds have also been leveraged as chiral reagents for alcohol resolution, chiral auxiliaries, mechanistic probes, as well as potential optoelectronic materials. This Minireview comprehensively summarizes the synthesis and synthetic applications of silicon‐stereogenic monohydrosilanes, particularly the advances in the transition‐metal‐catalyzed asymmetric synthesis of this class of functional molecules. [ABSTRACT FROM AUTHOR]

The silylation of a phosphine of OsH6(PiPr3)2 is performed via net‐metathesis between Si−C(spn) and H−C(sp3) σ‐bonds (n=2, 3). Complex OsH6(PiPr3)2 activates the Si−H bond of Et3SiH and Ph3SiH to give OsH5(SiR3)(PiPr3)2, which yield OsH4{κ1‐P,η2‐SiH‐[iPr2PCH(Me)CH2SiR2H]}(PiPr3) and R−H (R=Et, Ph), by displacement of a silyl substituent with a methyl group of a phosphine. Such displacement is a first‐order process, with activation entropy consistent with a rate determining step occurring via a highly ordered transition state. It displays selectivity, releasing the hydrocarbon resulting from the rupture of the weakest Si‐substituent bond, when the silyl ligand bears different substituents. Accordingly, reactions of OsH6(PiPr3)2 with dimethylphenylsilane, and 1,1,1,3,5,5,5‐heptamethyltrisiloxane afford OsH5(SiR2R′)(PiPr3)2, which evolve into OsH4{κ1‐P,η2‐GeH‐[iPr2PCH(Me)CH2SiR2H]}(PiPr3) (R=Me, OSiMe3) and R′−H (R′=Ph, Me). Exchange reaction is extended to Et3GeH. The latter reacts with OsH6(PiPr3)2 to give OsH5(GeEt3)(PiPr3)2, which loses ethane to form OsH4{κ1‐P,η2‐GeH‐[iPr2PCH(Me)CH2GeEt2H]}(PiPr3). [ABSTRACT FROM AUTHOR]

We have developed a palladium‐catalyzed addition of a C−Si bond of acylsilanes across a range of unactivated allenes. The reaction proceeds with complete regioselectivity, in which a silyl group binds to the central carbon of the allene, allowing for the straightforward access to functionalized alkenylsilane derivatives. [ABSTRACT FROM AUTHOR]

We report here a new method for the synthesis of organohydrosilanes from phenols and ketones. This method is established through reductive C−Si coupling of chlorohydrosilanes via unconventional Si−Cl cleavage. The reaction offers access to aryl‐ and alkenylhydrosilanes with a scope that is complementary to those of the established methods. Electron‐rich, electron‐poor, and ortho‐/meta‐/para‐substituted (hetero)aryl electrophiles, as well as cyclic and acyclic alkenyl electrophiles, were coupled successfully. Functionalities, including Grignard‐sensitive groups (e.g. primary amine, amide, phenol, ketone, ester, and free indole), acid‐sensitive groups (e.g. ketal and THP protection), alkyl‐Cl, pyridine, furan, thiophene, Ar‐Bpin, and Ar‐SiMe3, were tolerated. Gram‐scale reaction, incorporation of ‐Si(H)R2 into complex biologically active molecules, and derivatization of formed organohydrosilanes are demonstrated. [ABSTRACT FROM AUTHOR]

Intermolecular C−H silylation for the synthesis of acyclic silanes bearing a silicon‐stereogenic center in one enantiomeric form remains unknown to date. Herein, we report the first enantioselective intermolecular C−H silylation of heteroarenes for the synthesis of acyclic silicon‐stereogenic heteroarylsilanes. This process undergoes a rhodium‐catalyzed direct intermolecular dehydrogenative Si−H/C−H cross‐coupling, giving access to a variety of acyclic heteroarylated silicon‐stereogenic monohydrosilanes, including bis‐Si‐stereogenic silanes, in decent yields with excellent chemo‐, regio‐, and stereo‐control, which significantly enlarge the chemical space of the optically active silicon‐stereogenic monohydrosilanes. [ABSTRACT FROM AUTHOR]

Silylation of alcohols has generally been known to take place at the sterically most accessible less‐hindered hydroxy group. Herein, the catalyst‐controlled substrate‐selective silylation of primary alcohols, in which the selectivity was controlled independently of the innate reactivity of the hydroxy group, based on the steric environment, is reported. The chain‐length‐selective silylation of 1,n‐amino alcohol derivatives was achieved and 1,5‐amino alcohol derivatives showed outstandingly high reactivity in the presence of analogues with a shorter or longer chain length under catalyst‐controlled conditions. A highly substrate‐selective catalytic silylation of pentanol analogues was also developed, in which the remote functionality at C(5) from the reacting hydroxy groups was effectively discriminated on silylation. [ABSTRACT FROM AUTHOR]

Iridium catalysts containing dative nitrogen ligands are highly active for the borylation and silylation of C-H bonds, but chiral analogs of these catalysts for enantioselective silylation reactions have not been developed. We report a new chiral pyridinyloxazoline ligand for enantioselective, intramolecular silylation of symmetrical diarylmethoxy diethylsilanes. Regioselective and enantioselective silylation of unsymmetrical substrates was also achieved in the presence of this newly developed system. Preliminary mechanistic studies imply that C-H bond cleavage is irreversible, but not the rate-determining step.

Hydrosilyl ethers, generated in situ by the dehydrogenative silylation of cyclopropylmethanols with diethylsilane, undergo asymmetric, intramolecular silylation of cyclopropyl C-H bonds in high yields and with high enantiomeric excesses in the presence of a rhodium catalyst derived from a rhodium precursor and the bisphosphine (S)-DTBM-SEGPHOS. The resulting enantioenriched oxasilolanes are suitable substrates for the Tamao-Fleming oxidation to form cyclopropanols with conservation of the ee value from the C-H silylation. Preliminary mechanistic data suggest that C-H cleavage is likely to be the turnover-limiting and enantioselectivity-determining step.

Using a pyrazolate‐bridged dinucleating ligand that provides two proximate pincer‐type PNN binding sites ("two‐in‐one pincer"), different synthetic routes have been developed towards its dicobalt(I) complex 2 that features a twice deprotonated ligand backbone and two weakly activated terminal N2 substrate ligands directed into the bimetallic pocket. Protonation of 2 is shown to occur at the ligand scaffold and to trigger conversion to a tetracobalt(I) complex 4 with two end‐on μ1,2‐bridging N2; in THF 4 is labile and undergoes temperature‐dependent N2/triflate ligand exchange. These pyrazolate‐based systems combine the potential of exhibiting both metal–metal and metal–ligand cooperativity, viz. two concepts that have emerged as promising design motifs for molecular N2 fixation catalysts. Complex 2 serves as an efficient (pre)catalyst for the reductive silylation of N2 into N(SiMe3)3 (using KC8 and Me3SiCl), yielding up to 240 equiv N(SiMe3)3 per catalyst. [ABSTRACT FROM AUTHOR]

Using a pyrazolate‐bridged dinucleating ligand that provides two proximate pincer‐type PNN binding sites ("two‐in‐one pincer"), different synthetic routes have been developed towards its dicobalt(I) complex 2 that features a twice deprotonated ligand backbone and two weakly activated terminal N2 substrate ligands directed into the bimetallic pocket. Protonation of 2 is shown to occur at the ligand scaffold and to trigger conversion to a tetracobalt(I) complex 4 with two end‐on μ1,2‐bridging N2; in THF 4 is labile and undergoes temperature‐dependent N2/triflate ligand exchange. These pyrazolate‐based systems combine the potential of exhibiting both metal–metal and metal–ligand cooperativity, viz. two concepts that have emerged as promising design motifs for molecular N2 fixation catalysts. Complex 2 serves as an efficient (pre)catalyst for the reductive silylation of N2 into N(SiMe3)3 (using KC8 and Me3SiCl), yielding up to 240 equiv N(SiMe3)3 per catalyst. [ABSTRACT FROM AUTHOR]

The chemistry of silylated sulfuric acid, O2S(OSiMe3)2 (T2SO4, T=Me3Si; also known as bis(trimethylsilyl) sulfate), has been studied in detail with the aim of synthesizing the formal autosilylation products of silylated sulfuric acid, [T3SO4]+ and [TSO4]−, in analogy to the known protonated species, [H3SO4]+ and [HSO4]−. The synthesis of the [TSO4]− ion only succeeds when a base, such as OPMe3 that forms a weakly coordinating cation upon silylation, is reacted with T2SO4, resulting in the formation of [Me3POT]+[TSO4]−. [T3SO4]+ salts could be isolated starting from T2SO4 in the reaction with [T−H−T]+[B(C6F5)4]− or T+[CHB11Br6H5]− when a weakly coordinating anion is used as counterion. All silylated compounds could be crystallized and structurally characterized. [ABSTRACT FROM AUTHOR]

A Rh‐catalyzed asymmetric synthesis of silicon‐stereogenic dihydrodibenzosilines featuring axially chiral 6‐membered bridged biaryls is demonstrated. In the presence of a RhI catalyst with a chiral diphosphine ligand, a wide range of dihydrodibenzosilines containing both silicon‐central and axial chiralities are conveniently constructed in excellent enantioselectivities via dehydrogenative C(sp3)−H silylation. Absolute configuration analysis by single‐crystal X‐ray structures revealed a novel silicon central‐to‐axial chirality relay phenomenon, which we believe will inspire further research in the field of asymmetric catalysis and chiroptical materials. [ABSTRACT FROM AUTHOR]

Herein we report a versatile concept for the synthesis of fourfold functionalized, soluble pyrenes, peropyrenes, terropyrenes, and quarterropyrenes. They were obtained by a modular stepwise approach towards the rylene scaffold via Suzuki–Miyaura cross coupling, oxidative cyclodehydrogenation in the presence of caesium hydroxide under air, and finally zinc‐mediated reductive silylation. The silylated reaction products were characterized by X‐ray crystallography. The first example of a synthesized and crystallized quarterropyrene is presented and its oxidation reaction investigated. The functionalized ropyrenes were systematically characterized by means of UV/Vis–NIR and photoluminescence spectroscopy showing a bathochromic shift of 80 nm per naphthalene unit and a nearly linear increase of the extinction coefficients. Cyclic voltammograms and DFT calculations identify them as electron‐rich dyes and show a narrowing of the electrochemically determined HOMO–LUMO gap and lower oxidation potentials for the higher homologues. [ABSTRACT FROM AUTHOR]

The first iron‐catalyzed defluorosilylation of unactivated gem‐difluoroalkenes was developed, delivering gem‐disilylated alkenes and (E)‐silylated alkenes with excellent efficiency. This protocol features good functional group compatibility and excellent regio‐ and stereoselectivity, enabling the late‐stage silylation of biologically relevant compounds, thus providing good opportunities for applications in medicinal chemistry. Preliminary mechanistic studies and DFT calculations reveal that a nucleophilic addition and elimination of the second C−F bond might be involved in the disilylation catalytic system, demonstrating unusual reactivity characteristics of iron catalysis. [ABSTRACT FROM AUTHOR]

Tris(pentafluorophenyl)borane has been found to catalyze the two‐fold C(sp3)−H silylation of various trialkylamine derivatives with dihydrosilanes, furnishing the corresponding 4‐silapiperidines in decent yields. The multi‐step reaction cascade involves amine‐to‐enamine dehydrogenation at two alkyl residues and two electrophilic silylation reactions of those enamines, one inter‐ and one intramolecular. [ABSTRACT FROM AUTHOR]

Tris(pentafluorophenyl)borane has been found to catalyze the two‐fold C(sp3)−H silylation of various trialkylamine derivatives with dihydrosilanes, furnishing the corresponding 4‐silapiperidines in decent yields. The multi‐step reaction cascade involves amine‐to‐enamine dehydrogenation at two alkyl residues and two electrophilic silylation reactions of those enamines, one inter‐ and one intramolecular. [ABSTRACT FROM AUTHOR]

The use of an operationally convenient and stable silicon reagent (octamethyl‐1,4‐dioxacyclohexasilane, ODCS) for the selective silacyclization of (hetero)arenes via twofold C−H activation is reported. This method is compatible with N‐containing heteroarenes such as indoles and carbazoles of varying complexity. The ODCS reagent can also be utilized for silacyclization of other types of substrates, including tertiary phosphines and aryl halides. A series of mechanistic experiments and density functional theory (DFT) calculations were used to investigate the preferred pathway for this twofold C−H activation process. [ABSTRACT FROM AUTHOR]

A method for introducing dimethylphenylsilyl at the 4‐position in carbohydrates has been developed. Two C‐silylated glycosyl donors were prepared via levoglucosenone, starting from cellulose. The glycosylation properties were studied using three glucoside acceptors, a 3‐OH, 4‐OH, and 6‐OH. Compared with the 4‐deoxy variant, it was found that the anomeric selectivity was influenced more by the C‐2 substituents orientation than the silyl in the 4‐position. In general, the reactivity of these donors was higher than the corresponding 4‐deoxy‐analogue, albeit a competition experiment showed that the introduction of a C−Si increases the relative reactivity by a modest factor of around two. [ABSTRACT FROM AUTHOR]

A nonenzymatic dynamic kinetic resolution of acyclic and cyclic benzylic alcohols is reported. The approach merges rapid transition‐metal‐catalyzed alcohol racemization and enantioselective Cu‐H‐catalyzed dehydrogenative Si‐O coupling of alcohols and hydrosilanes. The catalytic processes are orthogonal, and the racemization catalyst does not promote any background reactions such as the racemization of the silyl ether and its unselective formation. Often‐used ruthenium half‐sandwich complexes are not suitable but a bifunctional ruthenium pincer complex perfectly fulfills this purpose. By this, enantioselective silylation of racemic alcohol mixtures is achieved in high yields and with good levels of enantioselection. [ABSTRACT FROM AUTHOR]

Electrophilic functionalisation of [Cp*Fe(η5‐P5)] (1) yields the first transition‐metal complexes of pentaphospholes (cyclo‐P5R). Silylation of 1 with [(Et3Si)2(μ‐H)][B(C6F5)4] leads to the ionic species [Cp*Fe(η5‐P5SiEt3)][B(C6F5)4] (2), whose subsequent reaction with H2O yields the parent compound [Cp*Fe(η5‐P5H)][B(C6F5)4] (3). The synthesis of a carbon‐substituted derivative [Cp*Fe(η5‐P5Me)][X] ([X]−=[FB(C6F5)3]− (4 a), [B(C6F5)4]− (4 b)) is achieved by methylation of 1 employing [Me3O][BF4] and B(C6F5)3 or a combination of MeOTf and [Li(OEt2)2][B(C6F5)4]. The structural characterisation of these compounds reveals a slight envelope structure for the cyclo‐P5R ligand. Detailed NMR‐spectroscopic studies suggest a highly dynamic behaviour and thus a distinct lability for 2 and 3 in solution. DFT calculations shed light on the electronic structure and bonding situation of this unprecedented class of compounds. [ABSTRACT FROM AUTHOR]

A rhodium(I)‐catalyzed enantioselective silylation of aliphatic C−H bonds for the synthesis of silicon‐stereogenic dihydrobenzosiloles is demonstrated. This reaction involves a highly enantioselective intramolecular C(sp3)−H silylation of dihydrosilanes, followed by a stereospecific intermolecular alkene hydrosilylation leading to the asymmetrically tetrasubstituted silanes. A wide range of dihydrosilanes and alkenes displaying various functional groups are compatible with this process, giving access to a variety of highly functionalized silicon‐stereogenic dihydrobenzosiloles in good to excellent yields and enantioselectivities. [ABSTRACT FROM AUTHOR]

The exhaustive trichlorosilylation of hexachloro‐1,3‐butadiene was achieved in one step by using a mixture of Si2Cl6 and [nBu4N]Cl (7:2 equiv) as the silylation reagent. The corresponding butadiene dianion salt [nBu4N]2[1] was isolated in 36 % yield after recrystallization. The negative charges of [1]2− are mainly delocalized across its two carbanionic (Cl3Si)2C termini (α‐effect of silicon) such that the central bond possesses largely C=C double‐bond character. Upon treatment with 4 equiv of HCl, [1]2− is converted into neutral 1,2,3,4‐tetrakis(trichlorosilyl)but‐2‐ene, 3. The Cl− acceptor AlCl3, induces a twofold ring‐closure reaction of [1]2− to form a six‐membered bicycle 4 in which two silacyclobutene rings are fused along a shared C=C double bond (84 %). Compound 4, which was structurally characterized by X‐ray crystallography, undergoes partial ring opening to a monocyclic silacyclobutene 2 in the presence of HCl, but is thermally stable up to at least 180 °C. [ABSTRACT FROM AUTHOR]

We report the synthesis of anionic diniobium hydride complexes with a series of alkali metal cations (Li+, Na+, and K+) and the counterion dependence of their reactivity with N2. Exposure of these complexes to N2 initially produces the corresponding side‐on end‐on N2 complexes, the fate of which depends on the nature of countercations. The lithium derivative undergoes stepwise migratory insertion of the hydride ligands onto the aryloxide units, yielding the end‐on bridging N2 complex. For the potassium derivative, the N−N bond cleavage takes place along with H2 elimination to form the nitride complex. Treatment of the side‐on end‐on N2 complex with Me3SiCl results in silylation of the terminal N atom and subsequent N−N bond cleavage along with H2 elimination, giving the nitride‐imide‐bridged diniobium complex. [ABSTRACT FROM AUTHOR]

The first aromatic C−H silylation between arylphosphines and hydrosilanes enabled by a ruthenium complex has been developed. The excellent ortho‐selectivity results from a four‐membered metallacyclic intermediate involving phosphorus chelation. The developed system can be extended to the benzylic C−H silylation of arylphosphines. Diverse silylated arylphosphines are produced, exhibiting broad functional group compatibility. Further functionalization of the products under mild conditions renders the formed compounds useful building blocks. [ABSTRACT FROM AUTHOR]

A method for the synthesis of benzylsilanes starting from the corresponding ammonium triflates is reported. Silyl boronic esters are employed as silicon pronucleophiles, and the reaction is catalyzed by copper(I) salts. Enantioenriched benzylic ammonium salts react stereospecifically through an SN2‐type displacement of the ammonium group to afford α‐chiral silanes with inversion of the configuration. A cyclopropyl‐substituted substrate does not undergo ring opening, thus suggesting an ionic reaction mechanism with no benzyl radical intermediate. [ABSTRACT FROM AUTHOR]

A copper‐catalyzed silylation of propargyl dichlorides was developed to access chloro‐substituted allenylsilanes under mild reaction conditions. Moreover, enantioenriched chloro‐substituted allenylsilanes can be synthesized in moderate to high yields and good enantioselectivities with this protocol. [ABSTRACT FROM AUTHOR]

A rhodium‐catalyzed system is introduced for in situ modification of biaryl‐type monophosphines with hydrosilanes through a PIII‐chelation‐assisted dehydrogenative silylation reaction. A series of ligands containing silyl groups with different steric and electronic properties were obtained with excellent regioselectivities. This method offers many advantages, including the use of commercially available phosphines, no requirement for an external ligand or oxidant, a broader substrate scope, high efficiency, and access to a single regioisomer. Based on the outstanding properties of the parent scaffolds, the silyl‐substituted phosphines serve as excellent ligands in Pd‐catalyzed asymmetric Suzuki coupling reactions. [ABSTRACT FROM AUTHOR]

We report a highly enantioselective catalytic protonation of bis‐silyl ketene acetals. Our method delivers α‐branched carboxylic acids, including nonsteroidal anti‐inflammatory arylpropionic acids such as Ibuprofen, in high enantiomeric purity and high yields. The process can be incorporated in an overall deracemization of α‐branched carboxylic acids, involving a double deprotonation and silylation followed by the catalytic asymmetric protonation. [ABSTRACT FROM AUTHOR]

A synergistic catalytic method combining photoredox catalysis, hydrogen‐atom transfer, and proton‐reduction catalysis for the dehydrogenative silylation of alkenes was developed. With this approach, a highly concise route to substituted allylsilanes has been achieved under very mild reaction conditions without using oxidants. This transformation features good to excellent yields, operational simplicity, and high atom economy. Based on control experiments, a possible reaction mechanism is proposed. [ABSTRACT FROM AUTHOR]

The ability to selectively forge C–heteroatom bonds by C−F scission is typically accomplished by metal catalysts, specialized ligands and/or harsh reaction conditions. Described herein is a base‐mediated defluorosilylation of unactivated C(sp2)−F and C(sp3)−F bonds that obviates the need for metal catalysts. This protocol is characterized by its simplicity, mild reaction conditions, and wide scope, even within the context of late‐stage functionalization, constituting a complementary approach to existing C−Si bond‐forming protocols. Base motive: A base‐promoted defluorosilylation of unactivated C(sp2)−F and C(sp3)−F bonds, obviating the need for transition‐metal catalysis, specialized ligands, or harsh reaction conditions, has been developed. The salient features of this method are the mild reaction conditions, ease of execution, and wide substrate scope, even within the context of late‐stage functionalization of advanced fluorinated building blocks, thus offering a complementary reactivity mode to existing silylation technologies. [ABSTRACT FROM AUTHOR]

A broad range of tertiary propargylic alcohols were kinetically resolved by catalyst‐controlled enantioselective silylation. This non‐enzymatic kinetic resolution is catalyzed by a Cu−H species and makes use of the commercially available precatalyst MesCu/(R,R)‐Ph‐BPE and a simple hydrosilane as the resolving reagent. Both alkyl,aryl‐ as well as dialkyl‐substituted propargylic alcohols participate, and especially high selectivity factors are achieved when the alkyne terminus carries a TIPS group, which also enables facile post‐functionalization in this position (s up to 207). Matchmaker: The commercially available precatalyst system MesCu/(R,R)‐Ph‐BPE couples Ph3SiH with the fast‐reacting enantiomer of racemic mixtures of tertiary propargylic alcohols. This non‐enzymatic kinetic resolution provides access to synthetically valuable and versatile enantiomerically enriched tertiary propargylic alcohols and the corresponding silyl ethers (see scheme). [ABSTRACT FROM AUTHOR]

Substituted arenes flanked by two bulky triethylsilyl groups were regiospecifically lithiated at the 5‐position with nBuLi⋅PMDTA at 25 °C. The resulting aryllithiums reacted with a broad range of electrophiles such as ketones, isocyanates, Weinreb amides, allyl bromides, and CO2 at 25 °C. These bis‐silylated arenes were then converted in simple reaction sequences into silyl‐free tetrasubstituted arenes. This remote lithiation was extended to 2,6‐bis(triethylsilyl)pyridine as well as 3,3′‐bis(triethylsilyl)biphenyl. Lithiation at theparaposition: The regiospecific remote lithiation of easily prepared o,o′‐bis(triethylsilyl)arenes and heteroarenes using nBuLi⋅PMDTA [PMDTA=MeN(CH2CH2NMe2)2] is reported. These lithiated (hetero)arenes react with a broad range of electrophiles to give silyl‐free tetrasubstituted products after further functionalizations. [ABSTRACT FROM AUTHOR]

The reaction of readily generated silyl lithium reagents with various aryl fluorides to provide the corresponding aryl silanes is reported. DFT calculations reveal that the nucleophilic aromatic substitution of the fluoride anion by the silyl lithium reagent proceeds through concerted ipso substitution. In contrast to the classical nucleophilic aromatic substitution, this concerted ionic silyldefluorination also occurs on more electron‐rich aryl fluorides. Just one step! Reactions of readily generated silyl lithium compounds with fluoroarenes provide the corresponding aryl silanes under very mild conditions. DFT calculations show that these transformations proceed through concerted nucleophilic aromatic substitution. [ABSTRACT FROM AUTHOR]

A diastereoselective [2,3] rearrangement of O‐silyl N‐sulfinyl N,O‐ketene acetals derived from chiral N‐acyl tert‐butanesulfinamides was developed, giving α‐sulfenyloxy carboxamides with excellent enantioselectivity. Enolization and subsequent silylation of N‐acyl tert‐butanesulfinamides initiate this aza variant of the Mislow–Evans rearrangement, in which the chirality at the sulfur atom in the rearrangement precursors is faithfully transferred to the α‐carbon stereocenter of the products. The Ellman sulfinamide, often used as a chiral ammonia equivalent, can serve in this rearrangement as a chiral precursor for the asymmetric synthesis of α‐oxygen‐functionalized carboxamides. "N" for nifty: An aza variant of the Mislow–Evans rearrangement was developed that relies on the formation of rearrangement precursors reminiscent of those required for the Ireland–Claisen rearrangement. The enolization and subsequent silylation of chiral N‐acyl tert‐butanesulfinamides initiated a [2,3] sigmatropic rearrangement with faithful chirality transfer from the sulfur atom of the sulfinyl group to the α‐carbon atom of the amide (see scheme). [ABSTRACT FROM AUTHOR]

Transition metal catalyzed C−H functionalization of organic compounds has proved to be a useful atom‐efficient strategy in organic synthesis. In contrast, main‐group‐element‐based catalytic processes for C−H functionalization have remained underexplored to date. Reported herein is the catalytic C(sp)−H silylation of a wide range of terminal alkynes with hydrosilanes by using a combination of B(C6F5)3 and an organic base such as triethylenediamine (DABCO). This protocol constitutes the first example of boron‐catalyzed C(sp)−H functionalization, offering a convenient route for the synthesis of a variety of alkynylsilanes. Experimental and computational studies have revealed that DABCO plays two crucial roles (Lewis base and Brønsted base) in this catalytic transformation. Double duty: The combination of B(C6F5)3 and an organic base, such as triethylenediamine (DABCO), serve as an excellent catalytic system for the C(sp)−H silylation of terminal alkynes with hydrosilanes. DABCO plays two crucial roles (Lewis base and Brønsted base) as revealed by experimental and DFT studies. [ABSTRACT FROM AUTHOR]

Abstract: The catalytic ring‐opening silylation of benzofurans has been achieved by employing a copper catalyst and 1,2‐di‐tert‐butoxy‐1,1,2,2‐tetramethyldisilane, which could be easily prepared and handled without special care. The reaction afforded (E)‐o‐(β‐silylvinyl)phenols with complete stereoselectivity. The scope of benzofurans was well explored, and functional groups such as chloro, fluoro, and acetal were compatible with the reaction conditions. DFT calculations were used to determine the energy profile of the silylation and the origin of the stereoselectivity. The silylated product was proven to be useful as a synthetic intermediate and subsequently underwent transformations such as Pd‐catalyzed cross‐coupling with iodoarenes. [ABSTRACT FROM AUTHOR]

Abstract: Disilylation of alkynes could provide rapid entry to synthetically useful 1,2‐bissilyl‐alkenes, but is currently limited to activated disilanes reacting in an intramolecular fashion. Reported herein is an efficient rhodium(I)‐catalyzed intermolecular disilylation of a wide array of alkynones with unactivated disilanes. Importantly, this reaction produces exclusively trans‐disilylation products, selectivity that has been rarely reported. These disilylation products were transformed into interesting pentacyclic vinyl silane ethers, among other additional synthetic manipulations. Mechanistic studies uncovered that the unactivated disilanes underwent facile Si−Si activation and crossover under the reaction conditions. [ABSTRACT FROM AUTHOR]

Abstract: Highly crystalline and (hydro)thermally stable zeolites with extra‐large pores [≥14‐ring (14‐R)] are desirable as catalysts. A novel zeolite, ECNU‐9, with an intersecting 14*12‐R channel system was rationally designed and synthesized by a building block strategy, in which the interlayer expansion of a two‐dimensional silicate structure was realized by combining organic amine assisted layer‐stacking reorganization and subsequent silylation with a square‐shaped single 4‐ring (S4R) silane, 1,3,5,7‐tetramethylcyclotetrasiloxane (TMCS). The PLS‐3 precursor was disassembled into building blocks and then intercalated with flexible and removable organic amine pillars to offer enough interlayer spacing for accommodating TMCS molecules. The additionally introduced building blocks interconnected the neighboring layers to construct new 14‐R and 12‐R pores. ECNU‐9 possesses a well‐ordered structure with a novel topology. The corresponding Ti‐ECNU‐9, with tetrahedral Ti ions in the framework, showed superior catalytic performance in the selective epoxidation of bulky alkenes. [ABSTRACT FROM AUTHOR]

Abstract: Reactive sulfur species (RSS) are biologically important molecules. Among them, H2S, hydrogen polysulfides (H2Sn,n>1), persulfides (RSSH), and HSNO are believed to play regulatory roles in sulfur‐related redox biology. However, these molecules are unstable and difficult to handle. Having access to their reliable and controllable precursors (or donors) is the prerequisite for the study of these sulfur species. Reported in this work is the preparation and evaluation of a series of O‐silyl‐mercaptan‐based sulfur‐containing molecules which undergo pH‐ or F−‐mediated desilylation to release the corresponding H2S, H2Sn, RSSH, and HSNO in a controlled fashion. This O→S relay deprotection serves as a general strategy for the design of pH‐ or F−‐triggered RSS donors. Moreover, we have demonstrated that the O‐silyl groups in the donors could be changed into other protecting groups like esters. This work should allow the development of RSS donors with other activation mechanisms (such as esterase‐activated donors). [ABSTRACT FROM AUTHOR]