Silylating Reagent Research Articles

Stability Effects of Selective Anion Abstraction from Cesium Lead Halide Perovskite Nanocrystals

The dynamic surface chemistry and stabilization of cesium lead halide perovskite nanocrystals (NCs) remain principal challenges for the use of these materials in many applications. Here, trimethylsilyl trifluoromethanesulfonate (Me3SiOTf) was used as a Lewis acidic reagent for quantitative and irreversible silylation and removal of anionic ligands from colloidal oleate- and oleylamine-capped CsPbBr3 and CsPbCl3 NCs. 1H NMR and FTIR spectroscopies, combined with elemental analysis, show strong binding of a population of anionic ligands to the NC surfaces. Surface anion exchange for trifluoromethanesulfonate also results in an increase in photoluminescence quantum yields. For CsPbCl3 NCs, Me3SiOTf treatment abstracts chlorides and destabilizes the NC lattice. The thermodynamic differences between these reactions and their implications are discussed.

Dual photoredox nickel-catalyzed silylation of aryl/heteroaryl bromides using hydrosilanes.

Dual Ni and Ir catalysis enables the preparation of arylsilanes having a (TMS)3Si substituent from the corresponding aryl bromides and (TMS)3SiH at 30 °C using visible-light irradiation. This protocol avoids strong bases, high temperature and air and moisture sensitive silyl reagents, providing the expected arylsilanes in moderate to good yields. The reaction was shown to proceed through a silyl radical, likely generated by hydrogen atom abstraction from (TMS)3SiH by a bromide radical.

Diphenylsilylsilanolates Enable the Transfer of a Wide Range of Silyl Groups.

Development of silylating reagents that can transfer a wide range of silyl groups has been a long-standing challenge. Herein we report sodium diphenylsilylsilanolates as new stable and handy silylating reagents that could be synthesized from chlorosilanes. The new reagents retain the ability of dimethylsilylsilanolates for the delivery of a variety of silyl groups in palladium-catalyzed silylation of aryl bromides irrespective of the steric and electronic properties of silyl groups to be transferred.

Environmental pseudotargeted metabolomics: A high throughput and wide coverage method for metabolic profiling of 1000-year paddy soil chronosequences

Pseudotargeted metabolomics is achieved by introducing an algorithm designed to choose ions for selected ion monitoring from identified metabolites. This method integrates the advantages of both untargeted and targeted metabolomics. In this study, environmental pseudotargeted metabolomics was established to analyze the soil metabolites, based on microwave assisted derivatization followed by gas chromatography–mass spectrometry analysis. The method development included the optimization of extraction factors and derivatization conditions, evaluation of silylation reagent types and matrix-dependent behaviors. Under the optimal conditions, the microwave oximation and silylation were completed in 5 min and 9 min. A total of 184 metabolites from 26 chemical classifications were identified in soil matrices. The method validation demonstrated excellent performance in terms of linearity (correlation coefficient > 0.99), repeatability (relative standard deviation (RSD) < 20 %), reproducibility (RSD < 25 %), stability (relative difference < 10 % within 18 h), and sensitivity (16–110 times higher signal-to-noise ratio). This developed method was applied to characterize the metabolite compositions and metabolic profiling in a 1000-year paddy soil chronosequence. The relative abundance of trehalose was highest in 6-(40.3 %), 60-(55.8 %), 300-(67.7 %)and 1000-(61.7 %)years paddy soil, respectively, but long-chain fatty acids were most abundant in marine sediment (57.4 %). Forty-two characteristic metabolites were considered as primarily responsible for discriminating and characterizing the paddy soil chronosequences development and seven major metabolic pathways were altered. In addition, GC–MS metabolite profile presented better discriminating power in paddy soil ecosystem changes than phospholipid fatty acids (PLFAs). Overall, environmental pseudotargeted metabolomics can provide a high throughout and wide coverage approach for performing metabolic profiling in the soil research.

High Mannose-Specific Aptamers for Broad-Spectrum Virus Inhibition and Cancer Targeting

High Mannose-Specific Aptamers for Broad-Spectrum Virus Inhibition and Cancer Targeting

Interlayer Modification of a Layered Silicate RUB-18 with 4-Phosphonophenylsilane and Its Surface Acidic Functions.

The interlayer silylation of a layered silicate H-RUB-18 (Si4O7(OH)2) using a new aromatic silylating reagent containing a phosphonic acid group (4-phosphonophenylsilane: PPS) was demonstrated (H-PPS-RUB-18). The phosphonic acid groups were attached to the silicate layers through the reaction of H-RUB-18 with (4-diethoxyphosphorylphenyl)-triethoxysilane (p-PPS-E), and the ester moieties were subsequently hydrolyzed with hydrochloric acid. H-PPS-RUB-18 is a solid acid, as indicated by the intercalation of various alkylamines and the catalytic acetalization of ketones. A systematic increase in interlayer spacing leading to surface acidic properties was obtained through intercalation with a series of alkylamines. In addition, H-PPS-RUB-18 was exfoliated, resulting in single-layer nanosheets with ca. 2.0 nm thickness. The catalytic acetalization of ketones was related to the interlayer spacing of the modified RUB-18.

Iron‐Catalyzed Silylation and Spirocyclization of Biaryl‐Ynones: A Radical Cascade Process toward Silylated Spiro[5.5]trienones

AbstractIron‐catalyzed cascade silyl radical addition/6‐exo‐trig cyclization/dearomatization of biaryl ynones has been developed. This approach uses silane as the precursor of silyl radical as well as silylation reagent, 1,10‐phenanthroline as the ligand, andtert‐butyl hydroperoxide (TBHP) as the oxidant. By employing this tandem process, a series of silylated spiro[5.5]trienones were prepared.magnified image

Rapid profiling of carboxylic acids in reservoir biodegraded crude oils using gas purge microsyringe extraction coupled to comprehensive two-dimensional gas chromatography-mass spectrometry

Carboxylic acids (CAs) are important molecular markers in petroleum geochemistry, which can indicate the origin, migration and biodegradation of oils. In this work, an easy and fast method was developed for the separation and analysis of CAs in crude oils by the combination of gas purge microsyringe extraction (GP-MSE) and comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC–MS). CAs in oils were firstly reacted with a silylation reagent to improve their volatility and thermal stability. The silylated CAs were then separated from oils together with light hydrocarbons with GP-MSE treatment at a relatively low temperature (200 °C). Subsequently, direct analysis of the extract solutions by GC × GC–MS was performed. Profited from the extremely high peak capacity of GC × GC, the signals of silylated CAs could be easily distinguished from hydrocarbon signals. Under optimal conditions, the extraction time and the solvent consumption of GP-MSE were 8 min and 150 μL, respectively. In the analysis of reservoir crude oils with different biodegradation degrees, abundant CA signals were successfully detected, and the contents of CAs were found to vary regularly with the biodegradation degree.

Ni-Catalyzed Decarboxylative Silylation of Alkynyl Carbonates: Access to Chiral Allenes via Enantiospecific Conversions.

A Ni-mediated decarboxylative silylation of alkynyl cyclic carbonates used as versatile propargylic surrogates is reported affording a wide range of highly substituted 2,3- and 3,4-allenol products in good yields. The formal cross-coupling between a tentative intermediate Ni(allenyl) and the silyl reagent was further extended to enantiospecific conversions providing access to chiral allene synthons. This protocol marks the first Ni-catalyzed propargylic silylation proceeding through an SN2' manifold.

Me2(CH2[double bond, length as m-dash]CH)SiCN: a bifunctional ethylene equivalent for Diels-Alder reaction based controllable tandem synthesis.

A bifunctional silyl reagent Me2(CH2CH)SiCN has been developed as a novel ethylene equivalent for the Diels–Alder (DA) reaction. The use of this reagent enables the controllable synthesis of value-added cyclohexenyl ketones or 2-acyl cyclohexancarbonitrile derivatives through a five- or six-step tandem sequence based on a Wittig/cyanosilylation/DA reaction/retro-cyanosilylation/isomerization sequence that involves a temporary silicon-tethered intramolecular DA reaction.

Sodium silylsilanolate as a precursor of silylcopper species

Silylcoppers function as convenient and effective sources of silicon functional groups. Commonly used precursors for those species have been limited to certain symmetric disilanes and silylboranes. This fact renders the development of silylcopper precursors desirable so that more diverse silyl groups could be efficiently delivered. Here we extend the utility of sodium silylsilanolates as competent precursors of silylcoppers. A silanolate unit operates as an auxiliary to transfer a variety of silyl groups to the copper centre, which was demonstrated in the copper-catalysed hydrosilylation of internal alkynes, α,β-unsaturated ketones, and allenes. Our mechanistic studies through DFT calculation suggested that a copper silylsilanolate undergoes intramolecular oxidative addition of the Si–Si bond to the copper centre to generate a silylcopper, in contrast to the typical formal σ-bond metathesis mechanism for conventional disilanes or silylboranes and copper alkoxides. Accordingly, sodium silylsilanolate has been established as an expeditious precursor of a variety of silylcopper species.

Layered Double Hydroxides as Reusable Catalysts for Cyclocondensation of Amidines and Aminoalcohols: Access to Multi-functionalized Oxazolines.

An efficient catalytic protocol based on reusable MgAl-layered double hydroxides has been developed for the synthesis of multi-functionalized oxazolines via the cyclocondensation of amidines and aminoalcohols. The developed method has a broad substrate scope and excellent functional group tolerance and uses a reusable catalyst. The catalyst can be conveniently recycled by filtration and reused for at least five times without obvious deactivation. Additionally, the selective ortho C-H silylation of oxazolines was performed using Ru(II) as the catalyst and triethyl silane as the silylating reagent, which proved to be a convenient and practical method for the synthesis of versatile organosilyl-functionalized oxazolines with advantageous biological and physical properties.

Simultaneous analysis of PAH urinary mono- and dihydroxylated metabolites by GC-MS-MS following SPE and two-stage derivatization

A new gas chromatography-tandem mass spectrometry method for the determination of mono- and dihydroxylated polycyclic aromatic hydrocarbon metabolites (OH-PAHs and diol-PAHs) in urine was developed and validated. Various sample preparation procedures were compared, namely liquid-liquid extraction (LLE), dispersive solid-phase extraction (dSPE), and SPE, alone or combined. A novel two-stage derivatization approach using 2 silylation reagents was developed, and an experimental procedure design was used to optimize the programmed temperature vaporization-solvent vent injection (PTV-SV) GC parameters. The method focused on 11 target compounds resulting from four- to five-ring suspected carcinogenic PAHs. SPE was identified as an acceptable and more convenient extraction method for all tested metabolites, with extraction rates ranging from 63 to 86% and relative standard deviations lower than 20%. The two-stage derivatization approach successfully allowed first the derivatization of OH-PAHs by MTBSTFA (N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide) and then diol-PAHs by BSTFA (N,O-bis(trimethylsilyl)trifluoroacetamide) in a single run. The limits of quantification were in the range of 0.01-0.02μgl-1 for OH-PAHs and 0.02-0.2μgl-1 for diol-PAHs. The intra- and interday precisions were lower than 10%. The method was applied to determine PAH metabolites in urine collected at the beginning and at the end of the working week from 6 workers involved in aluminum production. The mean diol-PAH levels at the end of the week were 10 to 20 times higher (0.86-2.34μgg-1 creatinine) than those of OH-PAHs (0.03-0.30μgg-1). These results confirmed the usefulness of this new analytical technique for detecting and characterizing metabolic patterns of PAHs in urine and assessing carcinogenic occupational exposures.

Cyclic (Alkyl)(amino)carbene Ligands Enable Cu‐Catalyzed Markovnikov Protoboration and Protosilylation of Terminal Alkynes: A Versatile Portal to Functionalized Alkenes**

AbstractRegioselective hydrofunctionalization of alkynes represents a straightforward route to access alkenyl boronate and silane building blocks. In previously reported catalytic systems, high selectivity is achieved with a limited scope of substrates and/or reagents, with general solutions lacking. Herein, we describe a selective copper‐catalyzed Markovnikov hydrofunctionalization of terminal alkynes that is facilitated by strongly donating cyclic (alkyl)(amino)carbene (CAAC) ligands. Using this method, both alkyl‐ and aryl‐substituted alkynes are coupled with a variety of boryl and silyl reagents with high α‐selectivity. The reaction is scalable, and the products are versatile intermediates that can participate in various downstream transformations. Preliminary mechanistic experiments shed light on the role of CAAC ligands in this process.

Ammonia Formation Catalyzed by a Dinitrogen‐Bridged Dirhenium Complex Bearing PNP‐Pincer Ligands under Mild Reaction Conditions**

AbstractA series of rhenium complexes bearing a pyridine‐based PNP‐type pincer ligand are synthesized from rhenium phosphine complexes as precursors. A dinitrogen‐bridged dirhenium complex bearing the PNP‐type pincer ligands catalytically converts dinitrogen into ammonia during the reaction with KC8 as a reductant and [HPCy3]BArF4 (Cy=cyclohexyl, ArF=3,5‐(CF3)2C6H3) as a proton source at −78 °C to afford 8.4 equiv of ammonia based on the rhenium atom of the catalyst. The rhenium‐dinitrogen complex also catalyzes silylation of dinitrogen in the reaction with KC8 as a reductant and Me3SiCl as a silylating reagent under ambient reaction conditions to afford 11.7 equiv of tris(trimethylsilyl)amine based on the rhenium atom of the catalyst. These results demonstrate the first successful example of catalytic nitrogen fixation under mild reaction conditions using rhenium‐dinitrogen complexes as catalysts.

Ammonia Formation Catalyzed by a Dinitrogen-Bridged Dirhenium Complex Bearing PNP-Pincer Ligands under Mild Reaction Conditions*.

A series of rhenium complexes bearing a pyridine-based PNP-type pincer ligand are synthesized from rhenium phosphine complexes as precursors. A dinitrogen-bridged dirhenium complex bearing the PNP-type pincer ligands catalytically converts dinitrogen into ammonia during the reaction with KC8 as a reductant and [HPCy3 ]BArF 4 (Cy=cyclohexyl, ArF =3,5-(CF3 )2 C6 H3 ) as a proton source at -78 °C to afford 8.4 equiv of ammonia based on the rhenium atom of the catalyst. The rhenium-dinitrogen complex also catalyzes silylation of dinitrogen in the reaction with KC8 as a reductant and Me3 SiCl as a silylating reagent under ambient reaction conditions to afford 11.7 equiv of tris(trimethylsilyl)amine based on the rhenium atom of the catalyst. These results demonstrate the first successful example of catalytic nitrogen fixation under mild reaction conditions using rhenium-dinitrogen complexes as catalysts.

Peptide Bond Formation of Amino Acids by Transient Masking with Silylating Reagents.

A one-pot peptide bond-forming reaction has been developed using unprotected amino acids and peptides. Two different silylating reagents, HSi[OCH(CF3)2]3 and MTBSTFA, are instrumental for the successful implementation of this approach, being used for the activation and transient masking of unprotected amino acids and peptides at C-termini and N-termini, respectively. Furthermore, CsF and imidazole are used as catalysts, activating HSi[OCH(CF3)2]3 and also accelerating chemoselective silylation. This method is versatile as it tolerates side chains that bear a range of functional groups, while providing up to >99% yields of corresponding peptides without any racemization or polymerization.

Non-target screening of organic compounds in offshore produced water by GC×GC-MS

Produced water is the largest by-product of oil and gas production. At off-shore installations, the produced water is typically reinjected or discharged into the sea. The water contains a complex mixture of dispersed and dissolved oil, solids and inorganic ions. A better understanding of its composition is fundamental to (1) improve environmental impact assessment tools and (2) develop more efficient water treatment technologies. The objective of the study was to screen produced water sampled from a producing field in the Danish region of the North Sea to identify any containing organic compounds. The samples were taken at a test separator and represent an unfiltered picture of the composition before cleaning procedures. The analytes were isolated by liquid-liquid extraction and derivatized using a silylation reagent to increase the volatility of oxygenated compounds. The final extracts were analyzed by comprehensive multi-dimensional gas chromatography coupled to a high-resolution mass spectrometer. A non-target processing workflow was implemented to extract features and quantify the confidence of library matches by correlation to retention indices and the presence of molecular ions. Approximately 120 unique compounds were identified across nine samples. Of those, 15 were present in all samples. The main types of compounds are aliphatic and aromatic carboxylic acids with a small fraction of hydrocarbons. The findings have implications for developing improved environmental impact assessment tools and water remediation technologies.

A Combined Computational and Experimental Study of Rh-Catalyzed C-H Silylation with Silacyclobutanes: Insights Leading to a More Efficient Catalyst System.

The study of new C-H silylation reagents and reactions remains an important topic. We reported that under Rh catalysis, silacyclobutanes (SCBs) for the first time were able to react with C(sp2)-H and C(sp3)-H bonds, however the underlying reasons for such a new reactivity were not understood. Through this combined computational and experimental study on C-H silylation with SCBs, we not only depict a reaction pathway that fully accounts for the reactivity and all the experimental findings but also streamline a more efficient catalyst that significantly improves the reaction rates and yields. Our key findings include: (1) the active catalytic species is a [Rh]-H as opposed to the previously proposed [Rh]-Cl; (2) the [Rh]-H is generated via a reductive elimination/β-hydride (β-H) elimination sequence, as opposed to previously proposed endocyclic β-H elimination; (3) the regio- and enantio-determining steps are identified; (4) and of the same importance, the discretely synthesized [Rh]-H is shown to be a more efficient catalyst. This work suggests that the [Rh]-H/diphosphine system should find further applications in C-H silylations involving SCBs.

Solid-phase synthesis of bi-functionalized porous organic polymer for simultaneous removal of Hg(II) and Pb(II)

The post-modification has been promoted as an efficient approach to achieve task-specific functionalization, but conventionally consumes huge amounts of solvent, which brings great challenges in environmental risks and energy efficiency. In this work, a bi-functionalized adsorbent is fabricated by a simple yet efficient solid-phase post-modification approach. Through one-pot ball milling at room temperature, 3-mercaptopropyltri-methoxysilane (3-MPTS) and 3-aminopropyltrimethoxysilane (3-APTS) are simultaneously grafted on the polyhydroxy naphthalenediol-based porous organic polymers (NTPOP). The operating conditions are optimized through an orthogonal experiment (L9(34)), which shows superior efficiency that at room temperature by consumption only 1 mL ethanol, it takes 2 h to successfully graft 1 mmol silylation reagent on 1g NTPOP at 300 rpm. The obtained bi-functionalized adsorbent NTPOP-SH-NH2 shows excellent adsorption performance with high Langmuir adsorption capacity of Hg(II) of 357 mg g−1 and Pb(II) of 212 mg g−1, and the second-order rate constant of 0.3003 mg−1 min-l and 0.1687 g mg−1 min-l, respectively. More importantly, in a natural water containing organic compounds and various inorganic salts, NTPOP-SH-NH2 shows strong tolerance with the adsorption performance of Hg(II) and Pb(II) maintains almost unchanged. Furthermore, NTPOP-SH-NH2 exhibits extensive applicability for multi heavy metals ions, such as Hg(II), Pb(II), Cd(II), Cr(III), and Ni(II), that an extremely high removal efficiency of higher than 99% was achieved for each metal ion when they co-exist in the natural aqueous solution. Therefore, this environmentally friendly solid-phase post-modification method provides a promising strategy for the synthesis of bi-functionalized adsorbents with high removal efficiency of heavy metal ions.