One-Pot Sequential Alcohol Activation and Nickel-Catalyzed Cross-Electrophile Coupling with Chlorosilanes

A formal deoxygenative silylation of primary alcohols is reported. The one-pot procedure consists of an in situ bromination of the alcohol and a subsequent nickel-catalyzed cross-electrophile coupling of the formed alkyl bromide and various vinyl-substituted chlorosilanes. The key to success is the compatibility of the nickel catalysis as well as the chlorosilane electrophile with the byproducts of the preceding bromination step, especially with triphenylphosphine oxide likely acting as a weak ligand for the excess nickel catalyst used.

Precision installation of silyl synthetic handles within arenes by regiocontrolled ruthenium C(sp 2)-H functionalization

The site-selective functionalization of C(sp 2)-H bonds represents a powerful strategy for the synthesis of structurally diverse compounds with broad applicability. Here we report efficient regioselective catalytic methods for the formation of benzyltrimethylsilanes through ruthenium-catalysed C(sp 2)-H silylmethylation. The developed protocols enable selective functionalization at both ortho and meta positions within arenes bearing N-based directing groups. The resulting silylmethyl compounds can undergo diverse transformations, including nucleophilic aromatic substitution, carbonyl addition, olefination and desilylation. Significantly, the regiodivergent installation of silylmethyl synthetic handles allows for the synthesis of the pharmaceutical losmapimod and could further be applied in direct late-stage functionalizations. Mechanistically, an essential role for biscyclometallated ruthenium(II) species has been found, with the formation of intermediate ruthenium(III) species indicated by paramagnetic NMR experiments. These synthetic inventions and mechanistic elucidations signify a transformative step within ruthenium-catalysed C(sp 2)-H functionalization, enabling diverse syntheses and providing a framework for future development.

Nickel-catalyzed stereospecific reductive cross-coupling of vinyl chlorosilanes with axially chiral biaryl electrophiles

Enantioenriched organosilanes are important chiral molecules in materials science and organic synthesis. The synthesis of axially chiral organosilanes is particularly significant in terms of applications. Herein, we report a Ni-catalyzed reductive cross-electrophile coupling of vinyl chlorosilanes with sterically hindered chiral biaryl electrophiles for the synthesis of atropisomeric biaryl organosilanes. Various enantioenriched axially chiral vinylsilanes are accessible in high efficiency under mild conditions. The synthetic transformations and applications of new chiral silicon-containing alkene ligands are demonstrated.

A unified flow strategy for the preparation and use of trifluoromethyl-heteroatom anions

The trifluoromethyl group (CF3) is a key functionality in pharmaceutical and agrochemical development, greatly enhancing the efficacy and properties of resulting compounds. However, attaching the CF3 group to heteroatoms such as sulfur, oxygen, and nitrogen poses challenges because of the lack of general synthetic methods and reliance on bespoke reagents. Here, we present a modular flow platform that streamlines the synthesis of heteroatom-CF3 motifs. Our method uses readily available organic precursors in combination with cesium fluoride as the primary fluorine source, facilitating the rapid generation of N-trifluoromethyl(R) [NCF3(R)], SCF3 (trifluoromethylthio), and OCF3 (trifluoromethoxy) anions on demand without reliance on perfluoroalkyl precursor reagents. This strategy offers a more environmentally friendly synthesis of trifluoromethyl(heteroatom)-containing molecules, with the potential for scalability in manufacturing processes facilitated by flow technology.

From Quaternary Carbon to Tertiary C(sp3)-Si and C(sp3)-Ge Bonds: Decyanative Coupling of Malononitriles with Chlorosilanes and Chlorogermanes Enabled by Ni/Ti Dual Catalysis

Transition-metal-catalyzed C-Si/Ge cross-coupling offers promising avenues for the synthesis of organosilanes/organogermanes, yet it is fraught with long-standing challenges. A Ni/Ti-catalyzed strategy is reported here, allowing the use of disubstituted malononitriles as tertiary C(sp3) coupling partners to couple with chlorosilanes and chlorogermanes, respectively. This method enables the catalytic cleavage of the C(sp3)-CN bond of the quaternary carbon followed by the formation of C(sp3)-Si/C(sp3)-Ge bonds from ubiquitously available starting materials. The efficiency and generality are showcased by a broad scope for both of the coupling partners, therefore holding the potential to synthesize structurally diverse quaternary organosilanes and organogermanes that were difficult to access previously.

Rh(II)-Catalyzed Si-H Insertion with Nosyl-hydrazone-Protected Aryl Donor Diazo Compounds

Dirhodium(II,II) paddlewheel catalysts were evaluated in silyl-hydrogen insertion reactions of aryl diazo compounds generated from o-nosyl hydrazones. The high reactivity of aryl diazo compounds necessitates their in situ generation from sulfonyl-protected hydrazones. Herein, we describe our efforts to evaluate this transformation utilizing Rh(II) catalysts, including those with tethered, axially coordinating ligands. The heteroleptic catalyst, Rh2(OAc)3(2-OX), provided the highest yield of silanes when dioxane was the solvent.

Stereospecific synthesis of silicon-stereogenic optically active silylboranes and general synthesis of chiral silyl Anions

Silicon-stereogenic optically active silylboranes could potentially allow the formation of chiral silyl nucleophiles as well as the synthesis of various chiral silicon compounds. However, the synthesis of such silicon-stereogenic silylboranes has not been achieved so far. Here, we report the synthesis of silicon-stereogenic optically active silylboranes via a stereospecific Pt(PPh3)4-catalyzed Si-H borylation of chiral hydrosilanes, which are synthesized by stoichiometric and catalytic asymmetric synthesis, in high yield and very high or perfect enantiospecificity (99% es in one case, and >99% es in the others) with retention of the configuration. Furthermore, we report a practical approach to generate silicon-stereogenic silyl nucleophiles with high enantiopurity and configurational stability using MeLi activation. This protocol is suitable for the stereospecific and general synthesis of silicon-stereogenic trialkyl-, dialkylbenzyl-, dialkylaryl-, diarylalkyl-, and alkylary benzyloxy-substituted silylboranes and their corresponding silyl nucleophiles with excellent enantiospecificity (>99% es except one case of 99% es). Transition-metal-catalyzed C-Si bond-forming cross-coupling reactions and conjugate-addition reactions are also demonstrated. The mechanisms underlying the stability and reactivity of such chiral silyl anion were investigated by combining NMR spectroscopy and DFT calculations.

Nickel-Catalyzed Reductive Coupling of Chlorosilanes

Organosilanes play essential roles in many important research areas. The use of readily available chlorosilanes to catalytically access these compounds is synthetically appealing but remains a long-standing challenge. Nickel-catalyzed reductive cross-coupling reaction has recently emerged as a promising protocol to arrive at this goal. This strategy allows the chlorosilanes to be coupled with various carbon electrophiles under mild conditions. These reactions afford organosilanes with improved molecular diversity, structural complexity, and functional group compatibility. This Concept article summarizes the recent advance on nickel-catalyzed reductive C-Si couplings of chlorosilanes.

Pd/Ming-Phos-Catalyzed Asymmetric Three-Component Arylsilylation of N-Sulfonylhydrazones: Enantioselective Synthesis of gem-Diarylmethine Silanes

A Pd-catalyzed enantioselective three-component reaction of N-sulfonylhydrazones, aryl bromides, and silylboronic esters is developed, enabling the synthesis of chiral gem-diarylmethine silanes in high enantioselectivity with the use of a newly identified Ming-Phos. Compared with N-tosyl, the more easily decomposed N-mesitylsulfonyl is more suitable as the masking group of electron-rich hydrazone to improve the reaction efficiency. The reaction features a broad scope concerning both coupling partners, high enantioselectivity, and mild reaction conditions. The ready access to enantiomers and utility of this catalytic method are also presented.

Inorganometallics (Transition Metal-Metalloid Complexes) and Catalysis

While the formation and breaking of transition metal (TM)-carbon bonds plays a pivotal role in the catalysis of organic compounds, the reactivity of inorganometallic species, that is, those involving the transition metal (TM)-metalloid (E) bond, is of key importance in most conversions of metalloid derivatives catalyzed by TM complexes. This Review presents the background of inorganometallic catalysis and its development over the last 15 years. The results of mechanistic studies presented in the Review are related to the occurrence of TM-E and TM-H compounds as reactive intermediates in the catalytic transformations of selected metalloids (E = B, Si, Ge, Sn, As, Sb, or Te). The Review illustrates the significance of inorganometallics in catalysis of the following processes: addition of metalloid-hydrogen and metalloid-metalloid bonds to unsaturated compounds; activation and functionalization of C-H bonds and C-X bonds with hydrometalloids and bismetalloids; activation and functionalization of C-H bonds with vinylmetalloids, metalloid halides, and sulfonates; and dehydrocoupling of hydrometalloids. This first Review on inorganometallic catalysis sums up the developments in the catalytic methods for the synthesis of organometalloid compounds and their applications in advanced organic synthesis as a part of tandem reactions.

Photocatalytic Synthesis of Diarylmethyl Silanes via 1,6-Conjugate Addition of Silyl Radicals to p-Quinone Methides

A novel photocatalytic method for the preparation of diarylmethyl silanes was reported through silyl radicals addition strategy to p-QMs (p-quinone methides). This protocol could tolerate a variety of functional groups affording the corresponding silylation products with moderate to excellent yields. The resulting silylation products could be easily converted into a series of bioactive GPR40 agonists and useful p-QMs precursors for the synthesis of compounds possessing both quaternary carbon centers and silicon substituents through simple operation. A plausible mechanism of silyl radicals to p-QMs was proposed on the basis of experimental results and previous literature.

Nickel-Catalyzed Reductive Cross-Coupling of Alkyl Bromides and Chlorosilanes

A novel nickel-catalyzed highly selective reductive cross-coupling of alkyl bromides and chlorosilanes to construct the C-Si bond has been developed. Under benign reaction conditions, a series of structurally interesting organosilanes can be accessed without Ni-catalyzed isomerization. The utility of this chemistry is illustrated by further transformations of the product. Moreover, the radical mechanism of the reaction is illustrated by control experiments.

Nickel-Catalyzed, Reductive C(sp3 )-Si Cross-Coupling of α-Cyano Alkyl Electrophiles and Chlorosilanes

A nickel/zinc-catalyzed cross-electrophile coupling of alkyl electrophiles activated by an α-cyano group and chlorosilanes is reported. Elemental zinc is the stoichiometric reductant in this reductive coupling process. By this, a C(sp3 )-Si bond can be formed starting from two electrophilic reactants whereas previous methods rely on the combination of carbon nucleophiles and silicon electrophiles or vice versa.

Activation of the Si–B interelement bond related to catalysis

Covering the past seven years, this review comprehensively summarises the latest progress in the preparation and application of Si–B reagents, including the discussion of relevant reaction mechanisms.

Synthesis of Alkyl Silanes via Reaction of Unactivated Alkyl Chlorides and Triflates with Silyl Lithium Reagents

The reaction of unactivated secondary and primary alkyl chlorides as well as primary alkyl triflates with silyl lithium reagents to access tetraorganosilanes is reported. These nucleophilic substitutions proceed in the absence of any transition metal catalyst under mild conditions in moderate to very good yields. The silyl lithium reagents are readily generated from the corresponding commercially available chlorosilanes. Enantioenriched secondary alkyl chlorides react with high stereospecificity under inversion of configuration.

Stereospecific and Chemoselective Copper-Catalyzed Deaminative Silylation of Benzylic Ammonium Triflates

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 SN 2-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.

Catalyst-controlled regiodivergent ring-opening C(sp3)-Si bond-forming reactions of 2-arylaziridines with silylborane enabled by synergistic palladium/copper dual catalysis

A Pd/Cu catalyst-controlled regiodivergent and stereospecific ring-opening C(sp³)–Si cross-coupling of 2-arylaziridines with silylborane has been developed and a new tandem reaction to give another regioisomer of silylamine has been discovered.

A catalyst-controlled regiodivergent and stereospecific ring-opening C(sp³)–Si cross-coupling of 2-arylaziridines with silylborane enabled by synergistic Pd/Cu dual catalysis has been developed. Just by selecting a suitable combination of catalysts, the regioselectivity of the coupling is completely switched to efficiently provide two regioisomers of β-silylamines (i.e., β-silyl-α-phenethylamines and β-silyl-β-phenethylamines) in good to high yields. Furthermore, a slight modification of the reaction conditions caused a drastic change in reaction pathways, leading to a tandem reaction to produce another regioisomer of silylamine (i.e., α-silyl-β-phenethylamines) in an efficient and selective manner.

Copper-catalyzed regiodivergent 1,4- and 1,6-conjugate silyl addition to diendioates: access to functionalized allylsilanes

A copper-catalyzed regioselective 1,4- and 1,6-conjugate addition of a silyl reagent to diendioates was established. Various 1,4- and 1,6-protosilylation products were obtained in good yields and with high regioselectivity via tuning the ligands used in the reactions. This protocol has provided a simple and efficient method for the synthesis of multisubstituted functionalized allylsilanes.

Synthesis and structure-activity relationships for new 6-fluoroquinoline derivatives with antiplasmodial activity

The substitution of 6-fluoroquinolines was modified in ring positions 2 and 4. The new compounds were tested in vitro for their activities against a sensitive and a multidrug resistant strain of Plasmodium falciparum. Some physicochemical parametres were calculated (log P, log D, ligand efficiency) or determined experimentally (permeability). The most promising compounds were tested for their in vivo activity against Plasmodium berghei in a mouse model. The 6-fluoro-2-{4-[(4-methylpiperazin-1-yl)methyl]phenyl}-N-[2-(pyrrolidin-1-yl)ethyl]quinoline-4-carboxamide possessed proper physicochemical properties and showed high antiplasmodial activity in vitro (IC₅₀ ≤ 0.0029 µM) and in vivo (99.6% activity).

Silicon-Carbon Bond Formation via Nickel-Catalyzed Cross-Coupling of Silicon Nucleophiles with Unactivated Secondary and Tertiary Alkyl Electrophiles

A wide array of cross-coupling methods for the formation of C-C bonds from unactivated alkyl electrophiles have been described in recent years. In contrast, progress in the development of methods for the construction of C-heteroatom bonds has lagged; for example, there have been no reports of metal-catalyzed cross-couplings of unactivated secondary or tertiary alkyl halides with silicon nucleophiles to form C-Si bonds. In this study, we address this challenge, establishing that a simple, commercially available nickel catalyst (NiBr2·diglyme) can achieve couplings of alkyl bromides with nucleophilic silicon reagents under unusually mild conditions (e.g., -20 °C); especially noteworthy is our ability to employ unactivated tertiary alkyl halides as electrophilic coupling partners, which is still relatively uncommon in the field of cross-coupling chemistry. Stereochemical, relative reactivity, and radical-trap studies are consistent with a homolytic pathway for C-X bond cleavage.