Search results for "trimethylsilyl"

An easy route to 1-germaindenes via a transmetallation zirconiumgermanium reaction

1993

Abstract Several 1-zirconaindenes ( 4 ) have been obtained easily by heating phenylmethylzirconocene with various symmetrical (R  R′  CH 3 , C 2 H 5 , n-C 3 H 7 , Si(CH 3 ) 3 and unsymmetrical (R  CH 3 , R′  Si(CH 3 ) 3 ) alkynes (RCCR′). Under similar experimental conditions, the ynamine, diethylaminotrimethylsilylethyne, led to a regioselective reaction. From the X-ray structure of the zirconaindene product, the trimethylsilyl group was found close to the zirconium atom. Compounds 4 with germanium tetrachloride afford new 1-germaindenes ( 7 ) characterized by 1 H and 13 C NMR and mass spectrometry, in good yield.

Biphenyl derivatives containing trimethylsilyl benzyl ether or oxime groups as probes for NO2 detection

2016

[EN] Four probes based in the use of a biphenyl moiety and functionalized with trimethylsilyl benzyl ether (P1 and P3) and oxime (P2 and P4) groups have been prepared and tested as optical probes for the detection of NO2. Reaction of NO2 with acetonitrile solutions of P2-P4 resulted in the formation of aldehydes 7 and 8 with a concomitant redshift of the absorption bands. Probe P2 displayed a bathochromic shift of 45 nm upon reaction with NO2 and was able to detect this poisonous gas at concentrations as low as 0.02 ppm. P2 was highly selective against NO2 and other gases (i.e. NO, CO2, H2S, SO2) and vapours of organic solvents (i.e. acetone, hexane, chloroform, acetonitrile or toluene) had…

ChemInform Abstract: (2-Phenyl-2-trimethylsilyl)ethyl (PTMSE) Esters - A Novel Carboxyl Protecting Group.

2010

Identification of diterpenes in canvas painting varnishes by gas chromatography-mass spectrometry with combined derivatisation.

2004

A derivatisation method that combines the formation of ethyl esters from the carboxylic groups and trimethylsilyl ethers from hydroxyl groups of the components of diterpenic resins is presented in this paper. This methodology involves two experimental steps: (1) formation of ethyl esters using ethyl chloroformate; and (2) the esterified compounds are lead to react with trimethylsilylimidazole to form the corresponding trimethylsilyl ethers. The main advantage of the proposed method is the possibility of performing simultaneously the analysis of amino acids from proteins, fatty acids from drying oils, and diterpenic compounds from natural resins usually found in works of art. This methodolog…

Diastereoselective Synthesis of Dialkylated Bis(phosphino)ferrocenes: Their Use in Promoting Silver-Mediated Nucleophilic Fluorination of Chloroquino…

2017

International audience; The diastereoselective synthesis of dialkylated ferrocenyl bis(phosphane)s bearing aryl, alkyl, and hetero- or polycyclic substituents on the phosphino groups is reported, together with their characterization in the solid state by X-ray structure analysis and in solution by multinuclear NMR spectroscopy. Introduction of various alkyl groups on the ferrocene backbone, namely, tert-butyl, isopropyl, and trimethylsilyl, has a significant influence on the stereoselectivity of the ensuing lithiation/phosphination reactions. Only the introduction of the tert-butyl groups ensures both a high yield and perfect diastereoselectivity, which leads to the exclusive formation of t…

Reactions of Alkenes and Alkynes with an Acyclic Silylene and Heavier Tetrylenes under Ambient Conditions

2014

Cycloaddition reactions of the acyclic silylene Si(SAriPr4)2 (AriPr4 = C6H3-2,6(C6H3-2,6-iPr2)2) with a variety of alkenes and alkynes were investigated. Its reactions with the alkynes phenylacetylene and diphenylacetylene and the diene 2,3-dimethyl-1,3-butadiene yielded silacycles (AriPr4S)2tiebar above startSi(CH═tiebar above endCPh) (1), (AriPr4S)2tiebar above startSi(PhC═tiebar above endCPh) (2), and (AriPr4S)2tiebar above startSiCH2CMeCMetiebar above endCH2 (3) at ambient temperature. The compounds were characterized by X-ray crystallography, 1H, 13C, and 29Si NMR spectroscopy, and IR spectroscopy. No reaction was observed with more substituted alkenes such as propene, (Z)-2-butene, te…

CCDC 171405: Experimental Crystal Structure Determination

2002

Related Article: F.Thomas, S.Schulz, M.Nieger, K.Nattinen|2002|Chem.-Eur.J.|8|1915|doi:10.1002/1521-3765(20020415)8:8<1915::AID-CHEM1915>3.0.CO;2-Z

Synthesis and gas chromatographic-mass spectrometric analysis of reduced compounds derived from 6 alpha- and 6 beta-hydroxy-11-deoxycorticosterone.

1989

Abstract A series of thirty two 6-hydroxylated steroids were synthesized by selective reduction of the 4–5 double bond, the 3-oxo group, and/or the 20-oxo group of 6α- and 6β-hydroxyDOC. The different reactions leading to the production of specific isomers are discussed. The gas chromatographic and spectrometric characteristics of the methoxime-trimethylsilyl (MO-TMS) or trimethylsilyl (TMS) derivatives of the isomers obtained are given. The gas chromatographic separation of the syn- and anti -isomers of the methoxime in position 3 was found to be characteristic of the configuration of the hydroxyl in position 6. The difference between methylene unit values of syn- and anti- isomers is much…

Reactions at Interfaces: Oxygenation of n-Butyl Ligands Anchored on Silica Surfaces with Methyl(trifluoromethyl)dioxirane

2011

The oxygenation of n-butyl and n-butoxy chains bonded to silica with methyl(trifluoromethyl)dioxirane (1) revealed the ability of the silica matrix to release electron density toward the reacting C(2)-H σ-bond through the Si-C(1) and Si-O(1) σ-bonds connecting the alkyl chain to the surface (silicon β-effect). The silica surface impedes neither the alkyl chain adopting the conformation required for the silicon β-effect nor dioxirane 1 approaching the reactive C(2) methylene group. Reaction regioselectivity is insensitive to changes in the solvation of the reacting system, the location of organic ligands on the silica surface, and the H-bonding character of the silica surface. Reaction rates…

Ethylene polymerization catalysts based on nickel(II) 1,4-diazadiene complexes: the influence of the 1,4-diazadiene backbone substituents on structur…

1998

Abstract Thermally sensitive dialkyl nickel complexes {DAD(H,H)}Ni(CH2SiMe3)2 and {DAD(Me,Me)}Ni(CH2SiMe3)2 [DAD(X,X)=2,6-iPr2C6H4–NC(X)–C(X)N–C6H4iPr2-2,6] were synthesized and were characterized by X-ray diffraction studies on single crystals. The substituents X on the backbone of the α-diimine ligand significantly influence the conformation of the 2,6-diisopropylphenyl substituents. This effect is thought to be of crucial importance for the polymerization of ethylene when {DAD(X,X)}NiBr2/MAO is used as catalyst. The influence of the catalyst structure, pressure, and temperature on the polymerization activity, molar mass, glass transition temperature, melting temperature and branching o…