Search results for "trimethylsilyl"

CCDC 750479: Experimental Crystal Structure Determination

2011

Related Article: D.Kurzbach, Shenglai Yao, D.Hinderberger, K.-W.Klinkhammer|2010|Dalton Trans.|39|6449|doi:10.1039/c001144d

CCDC 2090124: Experimental Crystal Structure Determination

2021

Related Article: Chris Gendy, J. Mikko Rautiainen, Aaron Mailman, Heikki M. Tuononen|2021|Chem.-Eur.J.|27|14405|doi:10.1002/chem.202102804

Insertion Reactions of Neutral Phosphidozirconocene Complexes as a Convenient Entry into Frustrated Lewis Pair Territory

2016

International audience; Neutral phosphidozirconocene complexes [Cp2Zr(PR2)Me] (Cp=cyclopentadienyl; 1a: R=cyclohexyl (Cy); 1b: R=mesityl (Mes); 1c: R=tBu) undergo insertion into the Zr-P bond by non-enolisable carbonyl building blocks (O=CRR), such as benzophenone, aldehydes, paraformaldehyde or CO2, to give [Cp2Zr(OCRRPR2)Me] (3-7). Depending on the steric bulk around P, complexes 3-7 react with B(C6F5)(3) to give O-bridged cationic zirconocene dimers that display typical frustrated Lewis pair (FLP)/ambiphilic ligand behaviour. Thus, the reaction of {[Cp2Zr(-OCHPhPCy2)][MeB(C6F5)(3)]}(2) (10a) with chalcone results in 1,4 addition of the Zr+/P FLP, whereas the reaction of {[Cp2Zr(-OCHFcPCy…

Enantioselective synthesis of pyrazolone α-aminonitrile derivatives via an organocatalytic Strecker reaction

2017

A new organocatalytic enantioselective Strecker reaction of pyrazolone-derived ketimine electrophiles has been developed. Using pseudo-enantiomeric squaramide catalysts the nucleophilic 1,2-addition of trimethylsilyl cyanide to the ketimines efficiently provides a direct entry to both enantiomers of pyrazolone α- aminonitrile derivatives at will in good yields and high enantioselectivities for a wide variety of substrates. peerReviewed

A gas chromatography-mass spectrometric method to determine skin-whitening agents in cosmetic products.

2010

An analytical method is proposed here to determine three allowed (kojic acid, azelaic acid and arbutin) and two forbidden (resorcinol and hydroquinone) skin-whitening agents in cosmetics. The method is based on gas chromatography coupled with mass spectrometric detection, which allows the two prohibited target compounds to be identified unequivocally by means of their mass spectra acquired in full-scan mode at the retention time of these compounds. Owing to their low volatility, target analytes are derivatized using N,O-bis-(trimethylsilyl)trifluoroacetamide (BSTFA) (containing 1% trimethylchlorosylane) prior to injection into the chromatographic system. The accuracy and precision of the pr…

Chromatographic and mass spectrometric characteristics of 20-dihydroaldosterone.

1992

The 20 alpha-reduced derivative of aldosterone, 20 alpha-dihydroaldosterone, was needed as reference compound in order to continue the studies on 18-hydroxylation in the Y-1 adrenal cell line. It was obtained by reduction of aldosterone with sodium borohydride. Analysis of the products of the reaction as methoxime trimethylsilyl (MO-TMS) derivatives by gas chromatography (GC) and GC-mass spectrometry (GC-MS) showed three possible forms of the compound. Their identification was confirmed by comparison with the products obtained by stereospecific reduction of aldosterone using 3 alpha,20 beta-hydroxysteroid dehydrogenase. Chromatographic behavior and mass spectra are given for the three forms…

The (2-phenyl-2-trimethylsilyl)ethyl-(PTMSEL)-linker in the synthesis of glycopeptide partial structures of complex cell surface glycoproteins.

2003

The (2-phenyl-2-trimethylsilyl)ethyl-(PTMSEL) linker represents a novel fluoride-sensitive anchor for the solid-phase synthesis of protected peptides and glycopeptides. Its cleavage is achieved under almost neutral conditions using tetrabutylammonium fluoride trihydrate in dichloromethane thus allowing the construction of complex molecules sensitive to basic and acidic media commonly required for the cleavage of standard linker systems. The advantages of the PTMSEL linker are demonstrated in the synthesis of glycopeptides from the liver intestine (LI)-cadherin and the mucin MUC1, bearing carbohydrate moieties such as N-linked chitobiose or O-linked sialyl-T(N)-residues. The synthesis of the…

2017

A hybrid bioinspired material with manganese(II) complexes grafted on the surface of a mesostructured porous silica is investigated. The Mn sites mimic the manganese-dependent dioxygenase (MndD), which is an enzyme that catalyses the oxidation of catechol derivatives. The metal complexes were introduced in the silica using a dinuclear complex [Mn2L2(Cl)2(μ-Cl)2] as a precursor with a clickable ligand N,N′-bis[(pyridin-2-yl)methyl]prop-2-yn-1-amine (L). Azide moieties covalently grafted on MCM-41 type mesoporous silica were utilised to anchor the manganese complex through Huisgen cycloaddition using CuBr(PPh3)3 as a catalyst. A second functional group – trimethylsilyl or pyridine—was grafted…

Efficient Synthesis of β-Halogeno Protected L-Alanines and Their β-Phosphonium Derivatives.

2003

Abstract Ring opening of oxazolines, prepared from l -serinates, with trimethylsilyl halides (TMSX) led to β-halogeno-N-benzoyl-α-amino esters in good to excellent yields. Quaternization of triphenylphosphine by the β-bromo or -iodo amino esters gave the corresponding β-phosphonium salts in overall yields of up to 93% and with e.e. >96%. Hydrolysis of the ester function afforded the phosphonium salt bearing an N-benzoyl-α-amino acid substituent, with partial racemization. However, the reaction of the TMSX with the carboxylic salt, prepared by saponification of the starting oxazoline ester, furnished the corresponding β-halogeno-N-benzoyl-α-amino acids in 70–95% yields. Quaternization of tri…

New nitrene functionalizations onto sidewalls of carbon nanotubes and their spectroscopic analysis

2010

Abstract The reactivity of p -toluenesulfonyl, methylsulfonyl and trimethylsilyl nitrene, derived from the corresponding azides, was studied towards single-walled carbon nanotubes (SWCNT) prepared by electric arc or HiPCO (High-pressure CO conversion) methods. The functionalized SWCNTs were analyzed by Raman, IR, and VIS/NIR spectroscopy. The spectroscopic results indicated that covalent modification of the SWCNTs was successful. While the IR measurements gave evidence of successful reaction in all studied cases, the Raman measurements indicated differences in the reactivity of the two tube types and between different nitrenes. VIS/NIR spectrum was measured for reaction with p -toluenesulfo…