Revealing Silylation of C(sp2)/C(sp3)–H Bonds in Arylphosphines by Ruthenium Catalysis

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.     

Recent advances in synthesis of organosilicons via radical strategies

Organosilicon compounds play an important role in the fields of materials science,pharmacy,and organic synthesis.The development of effective approaches for the preparation of these compounds have also become a research focus in organic synthesis.In recent years,free radical synthesis of organosilicons has been vigorously developed,which generally has the advantages of milder synthesis conditions,higher yields and selectivity,and free of precious metal catalysts compared with traditional strategies.This article reviews research progresses in the synthesis of organosilico n compounds by free radical pathways since 2016.In most cases,the radical silylation is achieved based on the reaction of silyl radicals,which are triggered by four routes including peroxide,transition-metal-induced peroxide decomposition,alkali,photocatalysis.The alkyl radicals can also initiate the radical silylation for the generation of C(sp~3)—Si bonds.     

Cu(I)–NHC‐Catalyzed Silylation of Allenes: Diastereoselective Three‐Component Coupling with Aldehydes

Copper‐catalyzed silylation of aryl allenes using a silylborane reagent affords vinyl silane building blocks with high efficiency. The use of a seven‐membered NHC ligand proved crucial for high regioselectivity. The catalytically generated allylcoppper intermediates were intercepted by aldehydes in a diastereoselective three‐component coupling to furnish homoallylic alcohols.     

Silylation Improves the Photodynamic Activity of Tetraphenylporphyrin Derivatives In Vitro and In Vivo

The effects of silyl and hydrophilic groups on the photodynamic properties of tetraphenylporphyrin (TPP) derivatives have been studied in vitro and in vivo. Silylation led to an improvement in the quantum yield of singlet oxygen sensitization for both sulfo and carboxy derivatives, although the silylation did not affect other photophysical properties. Silylation also improved the cellular uptake efficiency for both sulfo and carboxy derivatives, enhancing the in vitro photodynamic activity of the photosensitizer in U251 human glioma cells. The carboxy derivative (SiTPPC₄) was found to show higher cellular uptake efficiency and in vitro photodynamic activity than the corresponding sulfo derivative (SiTPPS₄), which indicates that the carboxy group is a more promising hydrophilic group than the sulfo group in the silylated porphyrin. SiTPPC₄ was found to show high selective accumulation efficiency in tumors, although almost no tumor selectivity was observed for the nonsilylated porphyrin. The concentration of SiTPPC₄ in tumors was 13 times higher than that in muscle 12 h after drug administration. We also studied tumor response after treatment and found that silylation enhanced in vivo photodynamic activity significantly. SiTPPC₄ shows higher photodynamic activity than NPe6 with white light irradiation.     

Graphene oxide‐bound electron‐deficient tin(IV) porphyrin: a highly efficient and selective catalyst for trimethylsilylation of alcohols and phenols with hexamethyldisilazane

The catalytic activity of graphene oxide‐bound tetrakis(p ‐aminophenyl)porphyrinatotin(IV) trifluoromethanesulfonate, [Sn^IV(TNH₂PP)(OTf)₂], in the trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) is reported. The prepared catalyst was characterized using inductively coupled plasma analysis, scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared and diffuse reflectance UV–visible spectroscopies. This heterogeneous catalyst was used for selective trimethylsilylation of various alcohols and phenols with HMDS in short reaction times and high yields. Also, the catalyst is of high reusability and stability, in that it was recovered several times without loss of its initial activity. The chemoselectivity of this catalytic system in the silylation of primary alcohols in the presence of secondary and tertiary alcohols and also phenols was investigated.     

Silylated Co/SBA-15 catalysts for Fischer-Tropsch synthesis

A series of silylated Co/SBA-15 catalysts were prepared via the reaction of surface Si-OH of SBA-15 with hexamethyldisilazane (HMDS) under anhydrous, vapor-phase conditions, and then characterized by FT-IR, N₂ physisorption, TG, XRD, and TPR-MS. The results showed that organic modification led to a silylated SBA-15 surface composed of stable hydrophobic Si-(CH₃)₃ species even after calcinations and H₂ reduction at 673 K. Furthermore, the hydrophobic surface strongly influenced both metal dispersion and reducibility. Compared with non-silylated Co/SBA, Co/S-SBA (impregnation after silylation) showed a high activity, due to the better cobalt reducibility on the hydrophobic support. However, S-Co/SBA (silylation after impregnation) had the lowest FT activity among all the catalysts, due to the lower cobalt reducibility along with the steric hindrance of grafted -Si(CH₃)₃ for the re-adsorption of α-olefins.     

Gas Chromatographic Study of Phosphatidyl Serines

Abstract

The reaction of silylating agents (BSA-TMCS) and phosphatidyl serines leads to the formation of 1,2-diglyceride trimethylsilyl (TMSi) ethers, along with small amounts of related 1,3-diglyceride trimethylsilyl ethers. The major product from a bovine phosphatidyl serine fraction was found to be 1-stearoyl-2-oleoylglycerol TMSi ether (the isomeric structure 1-oleoyl-2-stearoylglycerol TMSi ether may also be present). Related diglycerides were also found as products. The reaction products were identified by gas chromatography-mass spectrometry. The mechanism of the reaction is unknown, but it provides a way of studying the composition of phosphatidyl serine fractions without prior enzymic or chemical hydrolysis.     

Gas Chromatographic Analysis of Aminothiol Radioprotective Compounds

Abstract

A gas chromatographic method is described for aminothiols and disulfides. This method is based upon the formation of the trimethysilyl derivatives and their separation by gas chromatography. The kinetics of the derivative formation were investigated. A synthetic method for C4 to C6 aminothiols is given.     

Analysis of Organophosphorus-Based Nerve Agent Degradation Products by Gas Chromatography-Mass Spectrometry (GC-MS): Current Derivatization Reactions in the Analytical Chemist’s Toolbox

The field of gas chromatography-mass spectrometry (GC-MS) in the analysis of chemical warfare agents (CWAs), specifically those involving the organophosphorus-based nerve agents (OPNAs), is a continually evolving and dynamic area of research. The ever-present interest in this field within analytical chemistry is driven by the constant threat posed by these lethal CWAs, highlighted by their use during the Tokyo subway attack in 1995, their deliberate use on civilians in Syria in 2013, and their use in the poisoning of Sergei and Yulia Skripal in Great Britain in 2018 and Alexei Navalny in 2020. These events coupled with their potential for mass destruction only serve to stress the importance of developing methods for their rapid and unambiguous detection. Although the direct detection of OPNAs is possible by GC-MS, in most instances, the analytical chemist must rely on the detection of the products arising from their degradation. To this end, derivatization reactions mainly in the form of silylations and alkylations employing a vast array of reagents have played a pivotal role in the efficient detection of these products that can be used retrospectively to identify the original OPNA.