- Tetrabutylammonium butyldifluorodimethylsilicate and difluorodimethylphenylsilicate, new nucleophilic fluorinating reagents
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Tetrabutylammonium butyldifluorodimethylsilicate (TAMBS, 1a) and tetrabutylammonium difluorodimethylphenylsilicate (TAMPS, 1b) were conveniently prepared from the corresponding substituted fluorodimethylsilanes and tetrabutylammonium fluoride. Both fluorosilicates 1a, 1b are powerful nucleophilic fluorinating reagents which transform primary or secondary halides, tosylates, or mesylates to the corresponding fluorides in moderate to good yields.
- Kví?ala,Mysík,Paleta
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- Fourier Transform Infrared Spectrometric Determination of Alkyl Chain Conformation on Chemically Bonded Reversed-Phase Liquid Chromatography Packings
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A series of dimethyl-n-alkyl bonded phase sorbent ranging in length from C1 to C22 have been prepared and studied by use of Fourier transform infrared spectrometry (FT-IR).Spectra have been produced for each of the bonded phases, and comparisons are made to the corresponding silane reagents.By use of assignments reported for nonplanar conformations of normal alkanes, the supramolecular structure of these bonded phase systems is examined.The presence of absorption bands at 1341, 1354, and 1367 cm-1 in the bonded phase spectra confirms that bonded alkyl chains are bent, i. e., a significant fraction of the carbon-carbon bonds are in the "gauche" configuration.The degree of conformational disorder in chemically bonded stationary phases is shown to be comparable to that observed in the corresponding n-alkane liquids at room temperature and above.Phase transitions for the bonded phases are not observed at temperatures near or below the melting points of alkane and silane reagents of comparable length.Instead, the bonded phase chains are seen to retain a notable degree of disorder at low temperature.Finally, the effect of mobile phase environment on chain conformation is examined for a range of deuterated water/methanol mixtures varying from 70percent to 100percent methanol.Evidence is presented that in this range the mobile phase effects a significant increase in the order of the stationary phase.
- Sander, Lane C.,Callis, James B.,Field, Larry R.
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- A General and Selective Synthesis of Methylmonochlorosilanes from Di-, Tri-, and Tetrachlorosilanes
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Direct catalytic transformation of chlorosilanes into organosilicon compounds remains challenging due to difficulty in cleaving the strong Si-Cl bond(s). We herein report the palladium-catalyzed cross-coupling reaction of chlorosilanes with organoaluminum reagents. A combination of [Pd(C3H5)Cl]2 and DavePhos ligand catalyzed the selective methylation of various dichlorosilanes 1, trichlorosilanes 5, and tetrachlorosilane 6 to give the corresponding monochlorosilanes.
- Naganawa, Yuki,Nakajima, Yumiko,Sakamoto, Kei
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- Synthesis and characterization of dibutyltetramethyldisilazane-bonded silica phases for reversed-phase high-performance liquid chromatography
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A new silane, di-n-butyltetramethyldisilazane (DBTMDS), has been synthesized. Silanizations withh DBTMDS of a narrow-pore and a wide-pore silica yielded relatively high concentrations of bonded n-butyl ligands, of 4.22 and 4.09 μmol/m2, respectively. The chromatographic properties of the n-butyl bonded phase (C4-NH), synthesized with DBTMDS, were compared with n-butyl bonded phases (C4-CL) synthesized with n-butyldimethylchlorosilane (BDMCS) and Vydac-C4 under the same chromatographic conditions. The adsorption of basic compounds including N,N-diethylaniline (N,N-DEA), dansylarginine (Dns-Arg), and (phenyithio)hydantoin-arginine (PTH-Arg), as well as several polypeptides and small proteins including angiotensin I, angiotensin II, and lysozyme, was shown to be less for the C4-NH sorbents than for C4-CL and Vydac-C4 sorbents. While the S value for the basic protein lysozyme was significantly lower on the wide-pore C4-NH sorbent, the S and log k0 values for a range of selected proteins were comparable to those obtained with the Vydac-C4 sorbent. The tests of hydrolytic stability of the bonded phases showed significantly greater stability for the C4-NH sorbents than for the C4-CL sorbents under isocratic mobile-phase conditions of 10% and 40% acetonitrile with 0.1% TFA.
- Zhang, Renen,Xie, Zemin,Zhao, Rui,Li, Xiaohua,Liu, Guoquan,Aguilar, Marie-Isabel,Hearn, Milton T. W.
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p. 1861 - 1867
(2007/10/02)
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- Steroidal Silicon Side-Chain Analogues as Potential Antifertility Agents
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A number of silicon-substituted analogues of ethynylestradiol that exhibit modified and enhanced biological activities have been synthesized.Particularly noteworthy are a group of estradiol analogues that exhibit high antifertility potency and markedly reduced estrogenic activity.The best compounds synthesized are 17α-estradiol (5) and 17α-estradiol (33), which show a separation of antifertility from estrogenic activity in the rat.The results of structure-activity studies indicate a good correlation between the observed biological activities and the calculated van der Waals volumes of the three variable silicon substituents.
- Peters, Richard H.,Crowe, David F.,Tanabe, Masato,Avery, Mitchell A.,Chong, Wesley K. M.
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p. 646 - 652
(2007/10/02)
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- Selectivite de la scission Si-C dans des composes du type Me3SiCH2Σ; une synthese originale et sure de l'iodoacetate d'ethyle
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The regiochemistry of the electrophilic cleavage of the SiCsp3 bond in compounds Me3SiCH2Σ (Σ = Me, Pr, Cl, COOEt) and Me3SiCHΣ2 (Σ = Cl) has been investigated using ICl, Me3SiOSO2Cl and HO3SCl as the electrophiles.When Σ = Pr or Cl a regioselective cleavage of the Si-CH3 bond was observed, producing silylated chlorosulfonates or sulfates which often were new compounds.With Σ = COOEt a regiospecific splitting of the Si-CH2COOEt bond was observed.This confirms the synthetic potential of ethyl trimethylsilylacetate.
- Bordeau, M.,Djamei, S. M.,Dunogues, J.
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p. 413 - 417
(2007/10/02)
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- Process for the preparation of halogenosilanes
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Halogenosilanes are prepared from an organohalogenosilane and an organopolysiloxane as the starting materials by subjecting them to an intermolecular redistribution reaction in the presence of a monohydrochloride of a hexaalkylphosphotriamide. The thus prepared halogenosilanes, which are different from the starting halogenosilane reactant, are very useful in the silicone industry.
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