Organosilicon Reagents Research Articles

Photoinduced Hydrosilylation of Fluorinated Alkenes.

A visible-light-induced synthesis protocol for silylmonofluoroalkanes is described. The silylation of alkenyl fluorides using (trimethylsilyl)silanes as organosilicon reagents proceeds well under mild conditions via a sequential photoinduced single-electron transfer and protonation process. The protocol shows a broad substrate scope, transition-metal-free conditions, and high functional group tolerance. A wide variety of silylmonofluoroalkanes were obtained in generally good yields (up to 82%).

Low swelling and high mechanical strength organosilane hybrid polydivinylbenzene microspheres for hydrophilic interaction chromatography applications.

In this work, monodisperse organosilane hybrid polymer microspheres with a particle size of about 5µm were synthesized using seed swelling polymerization. The organosilicon reagent methacryloxypropyltrimethoxysilane was introduced into the polymer framework as a copolymerization monomer, and the crosslinking degree of the microspheres was improved by the hydrolysis-condensation reaction of siloxanes. The synthesized hybrid microspheres have good mechanical strength as well as low swelling, with swelling propensity values of 0.167 and 0.348 in methanol and acetonitrile, respectively. Hybrid microspheres modified with cysteine have a hydrophilic interaction chromatography/reversed-phase liquid chromatography mixed-mode retention mechanism. Compared to the commercial cysteine-modified silica column, the synthesized stationary phase has higher separation selectivity for partially acidic or basic samples and better basic resistance for use under high pH mobile phase conditions (at least 10).

Microwave-assisted palladium-catalyzed conjugate addition of arylsilanes to alkynes

Organosilanes, extensively employed as nucleophiles in coupling reactions, have seen limited application in the catalytic regioselective addition to unsaturated hydrocarbons. In this study, we present a microwave-assisted, palladium-catalyzed conjugate addition reaction involving arylsilanes and activated alkynes. This methodology for the catalytic functionalization of alkynes with organosilicon reagents offers a straightforward route to creating multisubstituted alkenes, boasting high regioselectivity. This efficient and versatile reaction tolerates a broad range of functional groups and substrates, heralding a potent new avenue in synthetic strategy.

Sequential C-F Bond Transformation of the Difluoromethylene Unit in Perfluoroalkyl Groups: A Combination of Fine-Tuned Phenothiazine Photoredox Catalyst and Lewis Acid.

A sequential process via photoredox catalysis and Lewis acid mediation for C-F bond transformation of the CF2 unit in perfluoroalkyl groups has been achieved to transform perfluoroalkylarenes into complex fluoroalkylated compounds. A phenothiazine-based photocatalyst promotes the defluoroaminoxylation of perfluoroalkylarenes with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) under visible light irradiation, affording the corresponding aminoxylated products. These products undergo a further defluorinative transformation with various organosilicon reagents mediated by AlCl3 to provide highly functionalized perfluoroalkyl alcohols. Our novel phenothiazine catalyst works efficiently in the defluoroaminoxylation. Transient absorption spectroscopy revealed that the catalyst regeneration step is crucial for the photocatalytic aminoxylation.

Sequential C−F Bond Transformation of the Difluoromethylene Unit in Perfluoroalkyl Groups: A Combination of Fine‐Tuned Phenothiazine Photoredox Catalyst and Lewis Acid

AbstractA sequential process via photoredox catalysis and Lewis acid mediation for C−F bond transformation of the CF2 unit in perfluoroalkyl groups has been achieved to transform perfluoroalkylarenes into complex fluoroalkylated compounds. A phenothiazine‐based photocatalyst promotes the defluoroaminoxylation of perfluoroalkylarenes with (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) under visible light irradiation, affording the corresponding aminoxylated products. These products undergo a further defluorinative transformation with various organosilicon reagents mediated by AlCl3 to provide highly functionalized perfluoroalkyl alcohols. Our novel phenothiazine catalyst works efficiently in the defluoroaminoxylation. Transient absorption spectroscopy revealed that the catalyst regeneration step is crucial for the photocatalytic aminoxylation.

Light-Triggered, Ni-Catalyzed Cyanation of Aryl Triflates with 1,4-Dicyanobenzene as the CN Source.

A light-triggered, Ni-catalyzed cyanation of aryl triflates was herein reported, which provides a benign photochemical synthesis of aryl nitriles using 1,4-dicyanobenzene as the CN source instead of HCN or a metallic CN source. This mild method uses a readily available bisphosphine ligand and a soluble organosilicon reagent as the reductant and is carried out under purple light without an external photocatalyst. This cyanation was effective for aryl triflates derived from phenols and bisphenols as well as lignin-derived phenolic compounds, demonstrating its potential utility for the synthesis of aryl nitriles from biomass.

Development of functionalized polymeric nanomaterial by organosiliconic reagent for boronate affinity-based dopamine recognition

The dopamine neurotransmitter is mainly responsible for endocrine functions in our body. The increase in the level of dopamine in the human body leads to many disorders such as schizophrenia, uncontrollable tics, addiction, increased tension, desire to act excessively, and carelessness. Decreased levels of dopamine cause problems such as malnutrition, stress, insomnia, and the use of antidepressants. Recognition of dopamine is crucial for clinical experiments. Therefore, the development of recognition surfaces of dopamine is essential for isolation, purification, and determination processes. This study, it was aimed to produce a polymeric nanomaterial that can recognize dopamine. For this purpose, p(HEMA) polymer was synthesized with surfactant-free emulsion polymerization method and silanized by organosilicon reagent (3-aminopropyl) triethoxylsilane (APTES) and modified with phenylboronic acid (PBA). Characterization of the p(HEMA)-APTES-PBA nanopolymeric system for dopamine recognition was performed with Scanning Electron Microscope(SEM), Energy Dispersive Spectrometry (EDS), Fourier Transform Infrared Spectroscopy (FTIR), Zeta-size/zeta-potential analysis, surface area calculations. Dopamine affinity of the p(HEMA)-APTES-PBA was optimized in terms of pH, time, concentration, buffer concentration, and buffer type parameters. Dopamine adsorption of p(HEMA)-APTES-PBA nanopolymers was 4,8 times more than epinephrine in specificity analysis. After the 7 adsorption–desorption cycles, the desorption rate was found to be 74.8 %. The developed nanopolymeric system is a convenient method with high adsorption capacity which allows easy and rapid extraction, isolation, and purification of dopamine.

Recent developments in difunctionalization of unsaturated hydrocarbons with organosilicon reagents.

Organosilicon compounds have attracted considerable attention because of their special biological activities. Direct difunctionalization of unsaturated hydrocarbons with organosilicon reagents for the efficient construction of synthetically valuable silicon-functionalized compounds are featured with a high step and atom economy, which could form carbon-silicon/carbon-carbon bonds or carbon-silicon/carbon-hetero bonds in one step. This review summarizes the recent advances on this topic based on different unsaturated hydrocarbons along with typical examples and mechanisms.

Stereoselective Palladium-Catalyzed Hiyama Cross-Coupling Reaction of Tetrasubstituted gem-Difluoroalkenes.

We herein describe a diastereoselective Pd(0)-catalyzed Hiyama cross-coupling reaction of gem-difluoroalkenes. The use of organosilicon reagents in this reaction is advantageous over other organometallic reagents by allowing the introduction of a wide range of functional groups, including challenging alkyl groups. Also conveniently, the additive TBAF was not required for (hetero)aryl-substituted difluoroalkenes.

Direct Synthesis of Unprotected Indolines Through Intramolecular sp3 C-H Amination Using Nitroarenes as Aryl Nitrene Precursors.

Given the prevalence of molecules containing nitro groups in organic synthesis, innovative methods to expand the reactivity of this functional group are of interest in both industrial and academic settings. In this report, a metal-free intramolecular benzylic sp3 C-H amination is disclosed using aryl nitro compounds as aryl nitrene precursors. Organosilicon reagent N,N'-bis(trimethylsilyl)-4,4'-bipyridinylidene (Si-DHBP) served as an efficient reductant in the transformation, enabling the in situ generation of aryl nitrene species for the direct, metal-free synthesis of unprotected 2-arylindolines from the corresponding nitroarene compounds.

Hexamethyldisilazane as a versatile organosilicon reagent for the synthesis of heterocycles (microreview)

Hexamethyldisilazane as a versatile organosilicon reagent for the synthesis of heterocycles (microreview)

Strategic Applications of the β‐Silicon Effect

AbstractOrganosilicon reagents are highly versatile and privileged scaffolds in modern synthetic chemistry, largely due to the range of transformations the groups are amenable to. The β‐Silicon effect is one of the fundamental phenomena underpinning the inherent reactivity of organosilicon reagents, allowing unsaturated organosilanes to undergo a range of electrophilic substitutions with a variety of nucleophiles. The application of the β‐Silicon effect in a range of organic transformations is reviewed with the discussion divided up based on the class of silane. The reactivity of these compounds towards carbon, heteroatom and metallic electrophiles is discussed from classical applications such as the Sakurai allylation to contemporary applications such as cross‐coupling chemistry. In addition, examples of these transformations in the context of methodology development and natural product synthesis are provided.magnified image

Copper‐Catalyzed N‐Arylation of Indoles and Anilines with Aryltrialkoxysilanes

AbstractHerein, we report an efficient copper‐catalyzed aerobic Chan‐Lam type N‐arylation of various indoles and anilines with structurally diverse aryltrialkoxysilanes under mild conditions. This silicon‐based protocol enables the efficient C−N cross‐coupling of indoles and anilines with user‐friendly organosilicon reagents by employing inexpensive and nontoxic Cu(OAc)2, which is efficient and practical without the addition of other ligands, bases, and metal oxidants. This transformation is compatible with a wide range of substrates, and typically proceeds with high efficiency as well as with good functional group compatibility. A plausible mechanism involving the formation of Cu(III) species in the reaction was tentatively proposed.

Reductively disilylated N-heterocycles as versatile organosilicon reagents.

The reductively disilylated N-heterocyclic systems 1,4-bis(trimethylsilyl)-1-aza-2,5-cyclohexadiene (1Si), 1,4-bis(trimethylsilyl)-1,4-dihydropyrazine (2Si) and its methyl derivatives (3Si and 4Si), and 1,1'-bis(trimethylsilyl)-4,4'-bipyridinylidene (5Si) are proficient organosilicon reagents owing to their low first vertical ionization potentials and the heterophilicity of the polarized N-Si bonds. These have prompted their reactivity as two-electron reductants or reductive silylations. These reactions benefit from the concomitant rearomatization of the N-heterocycles and liberation of trimethylsilyl halides or (Me3Si)2O, which are mostly volatile or easily removable byproducts. In this perspective, we have discussed the utilization of these reductively disilylated N-heterocyclic systems as versatile reagents in the salt-free reduction of transition metals (A) and main-group halides (B), in organic transformations (C) and in materials syntheses (D).

Preparation and Characterization of Magnetite – Silica Core – Shell Nanoparticles

In this study, two types of ligands were introduced onto the surface of magnetite nanoparticles by hydrolysis and condensation of organosilicon reagents: organosilane-tetraethoxysilane (TEOS) and aminoorganosilane - aminopropyltriethoxysilane (APTES). It is shown that coatings based on SiO2 solve a double problem: first, they prevent the aggregation of nanoparticles and the oxidation of magnetite; secondly, they allow the surface to be modified with various specific ligands for biomedical applications due to terminal groups. It was shown, that after the modification of TEOS and APTES (in argon and in air), the Fe3O4 content decreases to 66, 42, and 36%, respectively. The formation of a silicon framework on the magnetite surface due to Fe-O-Si and Si-O-Si bonds was determined by IR spectroscopy. The identification of surface amino groups is complicated due to the superposition of absorption bands of NH2- and OH-groups. This opens new prospective for creation of tailored nanocomposites containing magnetite nanoparticles. These materials can be further used as sorbents for various applications.

Alkoxyl-radical-mediated synthesis of functionalized allyl tert-(hetero)cyclobutanols and their ring-opening and ring-expansion functionalizations

tert -(Hetero)cyclobutanols are important synthetic building blocks. However, previous synthesis of these compounds has mainly focused on the nucleophilic addition of organometallic reagents to (hetero)cyclobutanones. Herein, we disclose a single-electron process for preparing allyl tert -(hetero)cyclobutanols with readily available organosilicon reagents. The success of the reaction is attributed to the favored radical 1,2-silyl transfer over β-carbon elimination of the alkoxyl radicals. The mechanism of the generation of carbon radicals from alkoxyl radicals is distinct from previous photoredox-mediated oxidation of hypervalent silicates. Our reaction shows broad substrate scope and wide functional-group tolerance. With the highly functionalized allyl tert -(hetero)cyclobutanols, we have achieved ring-opening reactions to synthesize thiolated 1,4-diketones and ring-expansion reactions to prepare seven-membered ring compounds. • Radical 1,2-silyl transfer over β-carbon elimination of alkoxy radicals • Ring-opening and ring-expansion reactions have been achieved • Broad substrate scope and wide functional-group tolerance The selectivity of a transformations is usually controlled by the reactivity of the reactive intermediate. (Hetero)cyclobutoxyl radicals are well known to be prone to undergo β-carbon elimination to generate carbon radicals. Our work disclosed here shows that radical 1,2-silyl transfer of (hetero)cyclobutoxy radicals is favored over β-carbon elimination. This radical C–Si bond-activation strategy is applied in the synthesis of functionalized allyl tert -(hetero)cyclobutanols. These compounds are challenging to prepare via previous two-electron processes, such as the addition of Grignard reagents to (hetero)cyclobutanones. Moreover, with the highly functionalized allyl tert -(hetero)cyclobutanols, we have achieved ring-opening reactions to synthesize thiolated ketones and ring-expansion reactions to prepare seven-membered ring compounds. Shen and coworkers present a photoredox process for synthesizing allyl tert -(hetero)cyclobutanols with readily available organosilicon reagents. The favored radical 1,2-silyl transfer over β-carbon elimination of the alkoxyl radicals is key to the success of the reaction. The reaction shows broad substrate scope and wide functional-group tolerance. With the highly functionalized allyl tert -(hetero)cyclobutanols, the authors have achieved ring-opening reactions to synthesize thiolated 1,4-diketones and ring-expansion reactions to prepare seven-membered ring compounds.

Silylated silicon–carbonyl complexes as mimics of ubiquitous transition-metal carbonyls

Transition-metal-carbonyl complexes are common organometallic reagents that feature metal-CO bonds. These complexes have proven to be powerful catalysts for various applications. By contrast, silicon-carbonyl complexes, organosilicon reagents poised to be eco-friendly alternatives for transition-metal carbonyls, have remained largely elusive. They have mostly been explored theoretically and/or through low-temperature matrix isolation studies, but their instability had typically precluded isolation under ambient conditions. Here we present the synthesis, isolation and full characterization of stable silyl-substituted silicon-carbonyl complexes, along with bonding analysis. Initial reactivity investigations showed examples of CO liberation, which could be induced either thermally or photochemically, as well as substitution and functionalization of the CO moiety. Importantly, the complexes exhibit strong Si-CO bonding, with CO→Si σ-donation and Si→CO π-backbonding, which is reminiscent of transition-metal carbonyls. This similarity between the abundant semi-metal silicon and rare transition metals may provide new opportunities for the development of silicon-based catalysis.

Direct transfer of tri- and di-fluoroethanol units enabled by radical activation of organosilicon reagents

Trifluoroethanol and difluoroethanol units are important motifs in bioactive molecules, but the methods to direct incorporate these units are limited. Herein, we report two organosilicon reagents for the transfer of trifluoroethanol and difluoroethanol units into molecules. Through intramolecular C-Si bond activation by alkoxyl radicals, these reagents were applied in allylation, alkylation and alkenylation reactions, enabling efficient synthesis of various tri(di)fluoromethyl group substituted alcohols. The broad applicability and general utility of the approach are highlighted by late-stage introduction of these fluoroalkyl groups to complex molecules, and the synthesis of antitumor agent Z and its difluoromethyl analog Z′.

Water plays a crucial role: Small molecule catalyzed C–C/C–X bond forming reactions using organosilicon reagents under “wet” conditions

Organocatalytic manipulation of silicon reagents, which enables the efficient formation of carbon–carbon (C–C) or carbon–heteroatom (C–X) bonds have been attracting considerable attention since the past few decades. In several instances, surprisingly, water is a remarkably essential molecule to promote the desired transformation to achieve superb outcomes in terms of reaction rates, chemical yields, and stereoselectivities. From the catalytic amount to solvent quantity, water plays a crucial role in the asymmetric/non-asymmetric catalytic transformations such as aldol reactions, Michael addition reactions, Mannich reactions, α-alkylation reactions, and other related strategies. In the current review, we present a comprehensive report on the recent advances of small molecule catalyzed addition reactions of organosilicon reagents under “wet” condition (46 examples). Examples featuring in the synthesis of complex natural products are also discussed.

Hierarchical structurized waste brick with opposite wettability for on-demand oil/water separation

Due to the variety of oily wastewater and complexity of separation system, it has put forward new challenge and requirement to separation materials for on-demand separation of various oil/water mixtures. Here, we reported a facile waste-to-resource strategy to rationally fabricate hierarchical ZnO nanopillars coating onto the surface of waste brick grains (ZnO/WBG) via simple physical process and in-situ growth technique. Specifically, the directly as-prepared ZnO/WBG possess superhydrophilic/underwater superoleophobic (UWSOB) properties and modified ZnO/WBG by organosilicon reagent possess quasi superhydrophobic/superoleophilic (SHOBI) properties. It is also worth noting that this discrete ZnO/WBG with opposite wettability can be accumulated into ZnO/WBG layer with numerous tortuous channel structure, making it feasible for on-demand separating various oil/water mixtures whether immiscible light- and heavy-oil/water mixtures or oil-in-water and water-in-oil emulsions. It has been demonstrated that the filter layers with opposite wettability exhibit high separation efficiency and flux, excellent chemical stability and admirable recyclability. Thus, this novel and cost-effective ZnO/WBG layer holds great promise for large-scale and versatile oil/water separation. Additionally, this work presents a sustainable perspective of effectively utilizing waste brick to construct workable functionalized materials with tremendous application potential, showing far-reaching value and significance in fundamental research and environmental protection.