- A method to derivatize surface silanol groups to Si-alkyl groups in carbon-doped silicon oxides
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A carbon-doped silicon oxide (CDO) finds use as a material with a low dielectric constant (k) for copper interconnects in multilayered integrated circuits (ICs). Hydrophilic silanol groups (Si-OH) on its surface, however, can attract moisture, thereby causing an undesirable increase in the dielectric constant. Modification of the exposed hydrophilic surface to a hydrophobic functional group provides one solution to this problem. We report here a strategy for converting surface Si-OH to hydrophobic silicon hydride (Si-H) without affecting the internal oxide network in CDO. The approach involves esterification of the exposed silanol to its triflate (silyltrifluoromethanesulfonate, Si-O-Tf), followed by reduction to Si-H with diisobutylaluminum hydride. Si-H is further modified by a photochemical reaction with an alkene (1-octadecene) to yield Si-R (R = -C18H37) to provide a more moisture resistant, and less polar Si-C as opposed to the Si-O backbone. Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectrometry (XPS), and measurements of the contact angle with water substantiated the successful conversion. The reaction scheme is versatile, transforming silanol groups to silicon hydride in widely varying chemical sites, from small molecules to the surfaces of silica gels, SiOx and CDO wafers. A comparison with the films (self-assembled monolayers) derivatized with the octadecyltrichlorosilane indicated that the new method leads to a thicker (≈5 nm) but more loosely packed hydrocarbon film with slightly lower contact angles.
- Darmakkolla, Srikar Rao,Tran, Hoang,Gupta, Atul,Rananavare, Shankar B.
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- Diastereoselectivity in the boron aldol reaction of α-alkoxy and α,β-bis-alkoxy methyl ketones
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In this work, using DFT calculations, we investigated the 1,4 and 1,5 asymmetric induction in boron enolate aldol reactions of α-alkoxy and α,β-bisalkoxy methyl ketones. We evaluated the steric influence of alkyl substituents at the α position and the stereoelectronic influence of the oxygen protecting groups at the α and β positions. Theoretical calculations revealed the origins of the 1,4 asymmetric induction in terms of the nature of the β-substituent. The synergistic effect between the α,β-syn and α,β-anti-bisalkoxy stereocenters was elucidated. In the presence of the β-alkoxy center, the reaction proceeds through the Goodman-Paton 1,5-stereoinduction model, experiencing a minor influence of the α-alkoxy center.
- Fernandes, Alessandra A. G.,Leonarczyk, Ives A.,Ferreira, Marco A. B.,Dias, Luiz Carlos
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supporting information
p. 3167 - 3180
(2019/03/26)
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- Chemoselective silyl transfer in the Mukaiyama aldol reaction promoted by super silyl Lewis acid
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In the silyl Lewis acid-promoted Mukaiyama aldol reaction, the steric and electronic properties of the silyl group on the silyl Lewis acid influence the reaction mechanism and product distribution. When super silyl triflates such as (TMS)3SiOTf and (TES)3SiOTf are used as Lewis acids, the silyl group of the silyl enol ether chemoselectively transfers to the product. The mechanistic details have been investigated using density functional theory (DFT) calculations.
- Sai, Masahiro,Akakura, Matsujiro,Yamamoto, Hisashi
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supporting information
p. 15206 - 15208
(2015/01/08)
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- Thermodynamic stability and reactivity of silylated bis(oxy)iminium ions
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(Chemical Equation Presented) Silylation of various nitronates with trialkylsilyl triflates was investigated by applying NMR techniques. In several cases, a flexible nitronate-bis(oxy)iminium ion (as an ion pair with triflate as counterion) equlibrium was found, and its thermodynamic parameters were determined. Elevation of temperature or dilution shifts this equilibrium toward the reactants. Activation parameters for the C,C-coupling reaction of silylated bis(oxy)iminium ions with a series of reference nucleophiles were determined. Estimated electrophilicity of bis(oxy)iminium ions allows one to count on C,C-coupling when partner nucleophilicity is N > 4.
- Khomutova, Yulia A.,Smirnov, Vladimir O.,Mayr, Herbert,Ioffe, Sema L.
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p. 9134 - 9140
(2008/03/17)
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- Process for producing novel naphthyridine derivatives
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A novel naphthyridine derivative showing high activity as a tachykinin receptor antagonist can be produced at high efficiency by reacting an acylating agent such as a carboxylic acid derivative with a compound represented by the formula (1): wherein R1, R2 and R3 represent independently a hydrogen atom, a lower alkyl group, a lower alkoxyl group, an aryl group, a heteroaryl group, an amino group, etc., and X1 and X2 represent respectively a halogen atom.
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- A non-enzymatic synthesis of (S)-(-)-rosmarinic acid and a study of a biomimetic route to (+)-rabdosiin
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The synthesis of (S)-(-)-rosmarinic acid (30) in 9% overall yield is described. The synthesis was achieved by a convergent route in which 3-(3′,4′-dihydroxyphenyl)-(S)-lactic acid (23) and caffeic acid (25), both appropriately protected, were coupled to produce a pentaallyl precursor 29, which was then deprotected to give (S)-(-)-rosmarinic acid (30). A triallyl derivative 35 was similarly prepared and converted to (+)-rabdosiin (41) and its (1R,2S) isomer (42) via a biomimetic oxidative free radical coupling-cyclization followed by deallylation. The coupling-cyclization gave a ratio of rabdosiin diastereomers unlike that found in nature. A preliminary study showed that methyl (R)-mandelyl sinapate (15) could be dimerized diastereoselectively to give a 1,2-trans thomasidioate diester (16). The synthesis of (S)-(-)-rosmarinic aid (30) in 9% overall yield is described. The synthesis was achieved by a convergent route in which 3- (3',4'-dihydroxyphenyl)-(S)-lactic acid (23) and caffeic acid (25), both appropriately protected, were coupled to produce a pentaallyl precursor 29, which was then deprotected to give (S)-(-)-rosmarinic acid (30). A triallyl derivative 35 was similarly prepared and converted to (+)-rabdosiin (41) and its (1R,2S) isomer (42) via a biomimetic oxidative free radical coupling- cyclization followed by deallylation. The coupling-cyclization gave a ratio of rabdosiin diastereomers unlike that found in nature. A preliminary study showed that methyl (R)-mandelyl sinapate (15) could be dimerized diastereoselectively to give a 1,2-trans thomasidioate diester (16).
- Bogucki, David E.,Charlton, James L.
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p. 1783 - 1794
(2007/10/03)
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- 1,2,4-trioxane compounds having antimalarial activity
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Novel 1,2,4-trioxanes which possess anti-malarial activity.
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- Enanthiospecific synthesis of longiborneol and longifolene
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A trimethylsilyl enol ether (34) derived from camphor (1) undergoes intramolecular Mukaiyama reaction to provide a tricyclic ketone (36) that can serve as a key intermediate in a new enantiospecific synthesis of longiborneol (11) and longifolene (12).
- Kuo, David L.,Money, Thomas
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p. 1794 - 1804
(2007/10/02)
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- REAGENTS AND SYNTHETIC METHODS 55. NEW METHODS FOR THE PREPARATION OF t-BUTYLDIMETHYLSILYL TRIFLATE AND TRIMETHYLSILYL TRIFLATE.
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An expeditious synthesis of t-butyldimethylsilyl triflate is described from triflic acid and t-butyldimethylsilane.Reaction between trichloromethyltrimethylsilane and triflic acid is also reported.
- Aizpurua, Jesus M.,Palomo, Claudio
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p. 6113 - 6114
(2007/10/02)
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- NEW METHOD FOR THE PREPARATION OF t-BUTYLDIMETHYLSILYL TRIFLATE
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t-Butyldimethylsilyl triflate is easily prepared from the reaction of triflic acid with isopropenyltrimethylsilane.
- Hudrlik, Paul F.,Kulkarni, Ashok K.
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p. 1389 - 1390
(2007/10/02)
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- STUDIES WITH TRIALKYLSILYLTRIFLATES: NEW SYNTHESES AND APPLICATIONS
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Syntheses and applications are described for three useful reagents for silylation of unreactive substrates, tert-butyldimethylsilyl, triisopropylsilyl, and octadecyldimethylsilyl triflate.
- Corey, E. J.,Cho, Hidetsura,Ruecker, Christoph,Hua, Duy H.
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p. 3455 - 3458
(2007/10/02)
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- Oxidation of Hydroquinone Silyl Esters to Quinones
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The electrochemical oxidation of trialkylsiloxybenzene derivatives was investigated using platinum and graphite anodes in either acetonitrile or methylene chloride solvent.Preparative oxidation of the bis(trimethylsilyl) ethers of hydroquinone, chlorohydroquinone, 2,5-di-tert-butylhydroquinone, and 9,10-dihydroxyanthracene gave the corresponding quinones in 80-90percent yield.Oxidation of 1,4-bis(trimethylsiloxy)-2-methoxybenzene in acetonitrile gave 3,6-dihydroxy-2,7-dimethoxydibenzofuran in 65percent yield.Oxidation of 1-methoxy-4-(trimethylsiloxy)benzene in methanolic acetonitrile produced 1,1-dimethoxy-2,5-cyclohexadien-4-one in 99percent yield.The cyclic voltammograms of the trimethylsilyl, triethylsilyl, and tert-butyldimethylsilyl ethers of 2,5-di-tert-butylhydroquinone were recorded using acetonitrile and methylene chloride solvents at 25 and -60 deg C.These compounds were found to react by initial one-electron oxidation to generate a cation radical which decomposes by silicon-oxygen bond cleavage to eventually form quinone.The relative rates for decomposition of the trimethylsilyl, triethylsilyl, and tert-butyldimethylsilyl ether cation radicals at -60 deg C were 10:5:1. tert-Butyldimethylsilyl chloride and tert-butyldimethylsilyl triflate were found to be stable toward cathodic reduction in dry methylene chloride and acetonitrile at potentials as negative as -2.1 vs.Ag/0.1 M AgNO3.Cyclic voltammetry indicated that reduction of 2,5-di-tert-butylbenzoquinone, anthraquinone, and naphthoquinone in the presence of tert-butyldimethylsilyl chloride resulted in reductive silylation.
- Stewart, Ray F.,Miller, Larry L.
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p. 4999 - 5004
(2007/10/02)
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