- The Thermal Elimination of Ketene from Alkyl Trimethylsilylacetates
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Alkyl trimethylsilylacetates readily undergo thermal elimination to give ketene and trimethylsilyl alkyl ethers; Arrhenius data have been obtained for this new unimolecular first-order reaction which involves a semi-concerted four-centre process.
- Taylor, Roger
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- CO Reduction to CH3OSiMe3: Electrophile-Promoted Hydride Migration at a Single Fe Site
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One of the major challenges associated with developing molecular Fischer-Tropsch catalysts is the design of systems that promote the formation of C-H bonds from H2 and CO while also facilitating the release of the resulting CO-derived organic products. To this end, we describe the synthesis of reduced iron-hydride/carbonyl complexes that enable an electrophile-promoted hydride migration process, resulting in the reduction of coordinated CO to a siloxymethyl (LnFe-CH2OSiMe3) group. Intramolecular hydride-to-CO migrations are extremely rare, and to our knowledge the system described herein is the first example where such a process can be accessed from a thermally stable M(CO)(H) complex. Further addition of H2 to LnFe-CH2OSiMe3 releases CH3OSiMe3, demonstrating net four-electron reduction of CO to CH3OSiMe3 at a single Fe site.
- Deegan, Meaghan M.,Peters, Jonas C.
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- Trifluormethansulfinsaeure-Azid und Trifluormethan-Schwefeloxidnitrid - Synthese und chemische Eigenschaften
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The synthesis of a perfluoroalkyl derivative of sulfanuric acid was attempted via the thermal decomposition of a) F3CSO2NPCl3 to yield OPCl3 as a byproduct, b) F3CSON3 to give the desired product by splitting off elemental nitrogen.However F3CSO2NPCl3 unexpectedly is stable up to 500 deg, when it looses mainly the F3C-group.Trifluoromethane sulfinic acidazide, F3CSON3, which we synthesised from the acid chloride and NaN3 at -40 deg starts to decompose as expected around -10 deg forming as the primary intermediate F3CSON, which can be formulated containing a S-N triple bond, and which proved to be extremely reactive.This trifluoromethan-sulfur oxide nitride oligomerizes spontaneously, or in presence of suitable compounds can be captured to yield various new compounds.With acetonitril a dithiatriazin is formed, with F3CSON3 an explosive sulfonimidoyl-azide, with trimethylsilyl azide, N-trimethylsilyl-trifluoromethan-sulfonimidoyl chloride.F3CSOCl yields an N-substituted sulfonimidoyl chloride in two diastereomeric forms.
- Bechtold, Thomas,Eingelbrecht, Alfred
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- The synthesis and rearrangement of cis-M(CO)4(PPh3)CH2I (M = Mn, Re)
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Manganese and rhenium iodomethyl complexes, cis-M(CO)4(PPh3)CH2I (1a, M = Mn; 1b, M = Re) have been prepared by treating the corresponding methoxymethyl complexes, cis-M(CO)4(PPh3)CH2OCH3 (2a, M = Mn; 2b, M = Re) with (CH3)3SiI.The attempted alternate syn
- Mandal, Santosh K.,Ho, Douglas M.,Orchin, Milton
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- Preparation of organic/inorganic hybrid hollow particles based on gelation of polymer vesicles
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In a previous communication, we have reported the study of novel organic/inorganic hollow particles based on a reactive amphiphilic diblock copolymer, poly(ethylene oxide)-block-poly[3-(trimethoxysilyl)propyl methacrylate] (PEO-b-PTMSPMA). The preparation
- Du, Jianzhong,Chen, Yongming
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- A Simple Post-Polymerization Modification Method for Controlling Side-Chain Information in Digital Polymers
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A three-step post-polymerization modification method was developed for the design of digitally encoded poly(phosphodiester)s with controllable side groups. Sequence-defined precursors were synthesized, either manually on polystyrene resins or automaticall
- K?nig, Niklas Felix,Al Ouahabi, Abdelaziz,Poyer, Salomé,Charles, Laurence,Lutz, Jean-Fran?ois
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- SILICON-CARBON UNSATURATED COMPOUNDS XVII. PHOTOCHEMICAL BEHAVIOR OF 1-METHYL-1-(TRIMETHYLSILYL)DIBENZOSILOLE AND 1-PHENYL-1-(TRIMETHYLSILYL)DIBENZOSILOLE
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The photolysis of 1-methyl-1-(trimethylsilyl)dibenzosilole (I) and 1-phenyl-1-(trimethylsilyl)dibenzosilole (II) has been investigated.Irradiation of I in the presence of acetone afforded 1-isopropoxy-1-methyl-2-(trimethylsilyl)dibenzosilole (III), while
- Ishikawa, Mitsuo,Tabohashi, Tatsuru,Kumada, Makoto,Iyoda, Jun
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- FLASH PYROLYSIS: A ROUTE TO "α-KETENIC ESTERS".
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3-Oxo 2-propenoic acid methyl ester has been prepared by flash vacuum pyrolysis and characterized by mass spectrometry and chemical trapping.Its four-membered cyclic dimers have been isolated.
- Jullien, J.,Pechine, J. M.,Perez, F.
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- The use of phosphorus pentafluoride as a fluorinating agent in organosilicon chemistry. III. Synthesis and characterization of some new fluorosiloxanes
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Although the silicon-oxygen bond of siloxanes and alkoxysilanes is readily cleaved by phosphorus pentafluoride, the silicon-hydrogen bond of hydrosiloxanes can be easily fluorinated at low temperatures by this reagent thus providing a convenient source of fluorosiloxanes. The synthesis and characterization of FSiH2OSiH3, (FSiH2)2O, F(CH3)HSiOSiH2CH3, and [F(CH3)HSi]2O are described.
- Kifer, Edward W.,Van Dyke, Charles H.
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- Contributions to the chemistry of halosilane adducts XVIII. On the nature of compounds of trimethylhalosilanes with 1,1,3,3-tetramethylguanidine and 2-trimethylsilyl-1,1,3,3-tetramethylguanidine: preparation and characterization of mono- and bis-(2-trimet
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1,1,3,3-Tetramethylguanidine (TMG) and 2-(trimethylsilyl)-1,1,3,3-tetramethyl-guanidine (TMSTMG) react with trimethylhalosilanes Me3SiHal in equimolar ratio with ionization of the Si-halogen bond to give the stable guanidinium salts Hal (
- Chaudhry, Subhash C.,Kummer, Dieter
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- Novel 10-I-3 hypervalent iodine-based compounds for electrophilic trifluoromethylation
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The synthesis of a new family of 10-I-3 hypervalent iodine compounds is described in which the CF3 functionality participates directly in the hypervalent bond. These materials are accessible by nucleophilic ligand substitution at iodine using Me3SiCF3 in the presence of a substoichiometric amount of fluoride. The expected T-shaped geometry at iodine was verified by X-ray crystallographic analyses of three of the products (1-trifluoromethyl-1,2-benziodoxol-3-(1 H)-one and two substituted 1-trifluoromethyl-1,3-dihydro-1,2-benziodoxoles). Preliminary results for the direct electrophilic transfer of the trifluoromethyl moiety onto organic nucleophiles show modest reactivity in polar aprotic solvents under relatively mild conditions. The overall process can be understood as a formal umpolung of the CF3 group.
- Eisenberger, Patrick,Gischig, Sebastian,Togni, Antonio
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- Enantioselective Synthesis of α-Aryl-β2-Amino-Esters by Cooperative Isothiourea and Br?nsted Acid Catalysis
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The synthesis of α-aryl-β2-amino esters through enantioselective aminomethylation of an arylacetic acid ester in high yields and enantioselectivity via cooperative isothiourea and Br?nsted acid catalysis is demonstrated. The scope and limitatio
- Zhao, Feng,Shu, Chang,Young, Claire M.,Carpenter-Warren, Cameron,Slawin, Alexandra M. Z.,Smith, Andrew D.
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supporting information
p. 11892 - 11900
(2021/04/28)
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- METHOD FOR PREPARING ALKYLALKOXYSILANES
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A method is useful for preparing alkylalkoxysilanes, such as alkylalkoxysilanes, particularly dimethyldimethoxysilane. The method includes heating at a temperature of 150°C to 400°C, ingredients including an alkyl ether and carbon dioxide, and a source of silicon and catalyst. The carbon dioxide eliminates the need to add halogenated compounds during the method.
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Paragraph 0037
(2020/03/29)
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- Catalytic Disproportionation of Formic Acid to Methanol by using Recyclable Silylformates
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A novel strategy to prepare methanol from formic acid without an external reductant is presented. The overall process described herein consists of the disproportionation of silyl formates to methoxysilanes, catalyzed by ruthenium complexes, and the production of methanol by simple hydrolysis. Aqueous solutions of MeOH (>1 mL, >70 percent yield) were prepared in this manner. The sustainability of the reaction has been established by recycling of the silicon-containing by-products with inexpensive, readily available, and environmentally benign reagents.
- Cantat, Thibault,Chauvier, Clément,Imberdis, Arnaud,Thuéry, Pierre
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supporting information
p. 14019 - 14023
(2020/06/09)
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- A methoxy trimethyl silane alcoholysis process (by machine translation)
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The invention relates to the field of chemical industry, in particular a methoxy trimethyl silane alcoholysis process. The invention is by the reaction tower at the top end of trimethylchlorosilane to enter the reaction vessel, the bottom of the methanol
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Paragraph 0007; 0008; 0009
(2017/04/22)
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- Amorphous silicon: New insights into an old material
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Amorphous silicon is synthesized by treating the tetrahalosilanes SiX4 (X=Cl, F) with molten sodium in high boiling polar and non-polar solvents such as diglyme or nonane to give a brown or a black solid showing different reactivities towards suitable reagents. With regards to their technical relevance, their stability towards oxygen, air, moisture, chlorine-containing reaction partners RCl (R=H, Cl, Me) and alcohols is investigated. In particular, reactions with methanol are a versatile tool to deliver important products. Besides tetramethoxysilane formation, methanolysis of silicon releases hydrogen gas under ambient conditions and is thus suitable for a decentralized hydrogen production; competitive insertion into the MeO-H versus the Me-OH bond either yields H- and/or methyl-substituted methoxy functional silanes. Moreover, compounds, such as MenSi(OMe)4-n (n=0-3) are simply accessible in more than 75% yield from thermolysis of, for example, tetramethoxysilane over molten sodium. Based on our systematic investigations we identified reaction conditions to produce the methoxysilanes MenSi(OMe)4-n in excellent (n=0:100%) to acceptable yields (n=1:51%; n=2:27%); the yield of HSi(OMe)3 is about 85%. Thus, the methoxysilanes formed might possibly open the door for future routes to silicon-based products. Amorphous silicon is easily synthesized from tetrahalosilanes SiX4 (X=Cl, F) and molten sodium in different solvents. Reactivity studies prove the resulting materials as versatile tools for the formation of technical important silanes, such as the silicon chloro-, alkoxy-, and methylalkoxy-substituted derivatives (see figure; bl=black, br=brown).
- Spomer, Natalie,Holl, Sven,Zherlitsyna, Larissa,Maysamy, Fariba,Frost, Andreas,Auner, Norbert
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p. 5600 - 5616
(2015/03/30)
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- Preparation of nano silica supported sodium hydrogen sulfate: As an efficient catalyst for the trimethyl, triethyl and t-butyldimethyl silylations of aliphatic and aromatic alcohols in solution and under solvent-free conditions
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Nano silica supported sodium hydrogen sulfate has been prepared by mixing NaHSO4 with activated Nano silicagel. We wish to report a new method for the synthesis of trimethyl (TMS), triethyl (TES) and t-butyldimethyl silyl (TBS) ethers from benzylic, allylic, propargylic alcohols, phenols, naphtholes and some of phenolic drugs in the solution and under solvent-free conditions.
- Abri, Abdolreza,Ranjdar, Somayeh
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p. 929 - 934
(2014/10/16)
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- Silylated derivatives of azasilacyclopentanes
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Catalytic intramolecular cyclization of 3-aminopropylalkoxysilanes and 3-aminopropylalkoxydisiloxanes in the presence of hexamethyldisilazane has been studied; structure and reactivity of the formed azasilacyclopentanes have been investigated. In particul
- Salikhov,Kopylov,Shragin
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p. 875 - 882
(2014/07/22)
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- {[[K.18-Crown-6]Br3}n: A tribromide catalyst for the catalytic protection of amines and alcohols
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{[K.18-Crown-6]Br3}n, a unique tribromide-type catalyst, was utilized for the N-boc protection of amines and trimethylsilylation (TMS) and tetrahydropyranylation (THP) of alcohols. The method is general for the preparation of N-boc derivatives of aliphatic (acyclic and cyclic) and aromatic, and primary and secondary amines and also various TMS-ethers and THP-ethers. The simple separation of the catalyst from the product is one of the many advantages of this method.
- Chehardoli, Gholamabbas,Zolfigol, Mohammad Ali,Derakhshanpanah, Fateme
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p. 1730 - 1733
(2013/10/21)
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- REAGENT FOR TESTING PURIFICATION CAPACITY OF RADIOACTIVE GAS IN NUCLEAR POWER PLANT, PREPARATION METHOD THEREOF AND IODIDE FILTER TESTING EQUIPMENT USING THIS REAGENT
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Disclosed are a reagent for testing the purification capacity of a radioactive gas in a nuclear power plant, preparation method thereof and an iodide filter testing equipment using this reagent. The reagent is prepared by mixing methyl phosphate compound or dimethyl acetal compound, acetonitrile, trimethyl chlorosilane and radioactive iodine sources and carrying out a reaction at a temperature of 20°C-50 °C under an inert gas for 10-40 min. The prepared products except methyl iodide are non-toxic or little toxic to the nuclear grade impregnated activated carbon in the iodide filter.
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Paragraph 0062
(2013/04/25)
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- COMPOUNDS CONTAINING PERFLUOROALKYL-CYANO-ALKOXY-BORATE ANIONS OR PERFLUOROALKYL-CYANO-ALKOXY-FLUORO-BORATE ANIONS
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The present invention relates to compounds containing perfluoroalkyl-cyano-alkoxy-borate anions or perfluoroalkyl-cyano-alkoxy-fluoro-borate anions, ((per)fluoro)phenyl-cyano-alkoxy-borate anions or ((per)fluoro)phenyl-cyano-alkoxy-fluoro-borate anions or phenyl-cyano-alkoxy-borate anions which are monosubstituted or disubstituted with perfluoroalkyl groups having 1 to 4 C atoms or phenyl-cyano-alkoxy-fluoro-borate anions which are monosubstituted or disubstituted with perfluoroalkyl groups having 1 to 4 C atoms, the preparation thereof and the use thereof, in particular as part of electrolyte formulations for dye sensitized solar cells.
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Page/Page column 14
(2012/12/13)
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- ELECTROLYTE FORMULATIONS CONTAINING CYANO-ALKOXY-BORATE ANIONS
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The present invention relates to electrolyte formulations containing cyano-alkoxy-borate anions, their preparation and their use, in particular as part of electrolyte formulations for electrochemical or optoelectronic devices and special compounds containing cyano-alkoxy-borate anions.
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Page/Page column 57
(2012/04/17)
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- METHOD OF PRODUCING A HYDROLYZABLE SILICON-CONTAINING COMPOUND
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The present invention provides a safe, inexpensive, and high yield means of producing a hydrolyzable silicon-containing compound, e.g., an organooxysilane and the like. A compound (A) represented by the general formula R1-O-R2 wherein R1 represents a C4-30, substituted or unsubstituted, tertiary alkyl group or aralkyl group and R2 represents a C1-30, substituted or unsubstituted, monovalent hydrocarbyl group or acyl group, is reacted in the presence of a Lewis acid catalyst with a halosilane (B) represented by the general formula R3mSiX4-m wherein R3 represents the hydrogen atom or a C1-30 substituted or unsubstituted monovalent hydrocarbyl group, X is independently bromine or chlorine, and m represents an integer from 0 to 3.
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Page/Page column 18; 20
(2012/07/14)
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- Practical conversion of chlorosilanes into alkoxysilanes without generating HCl
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Alcohol-free: A versatile, efficient, and practical synthesis of alkoxysilanes without generation of HCl involves the reaction of chlorosilanes with unsymmetrical ethers in the presence of a Lewis acid (see scheme). The reaction proceeds through selective cleavage of C-O bonds and is superior to conventional processes. Industrially feasible reagents are used and only one by-product results. Copyright
- Wakabayashi, Ryutaro,Sugiura, Yasushi,Shibue, Toshimichi,Kuroda, Kazuyuki
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supporting information; experimental part
p. 10708 - 10711
(2011/12/05)
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- Reactions of CF3-substituted boranes with α-diazocarbonyl compounds
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Boranes substituted with a CF3-group can be generated from methyl boronic esters RB(OMe)2 and Me3SiCF3/KF followed by treatment with Me3SiCl. These boranes are stable only in coordinating solvents, and due to the increased Lewis acidity of boron, react rapidly with α-diazocarbonyl compounds to give the products of transfer of the organic group from boron. Alkyl, aryl, vinyl, and alkynyl boronic esters can be used in this reaction.
- Elkin, Pavel K.,Levin, Vitalij V.,Dilman, Alexander D.,Struchkova, Marina I.,Belyakov, Pavel A.,Arkhipov, Dmitry E.,Korlyukov, Alexander A.,Tartakovsky, Vladimir A.
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supporting information; experimental part
p. 5259 - 5263
(2011/10/31)
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- The pentamethylcyclopentadienylsilicon(II) cation as a catalyst for the specific degradation of oligo(ethyleneglycol) diethers
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Catalytic open sandwiches: Oligo(ethyleneglycol) diethers RO(CH 2CH2O)nR are degraded by the unusual catalyst Cp Si+ (see scheme). The open coordination sphere at silicon allows up to four Si-O contacts; crystal structure data of the reactive compounds [Cp Si(dme)]+BR4- and [Cp Si([12]crown-4)] +BR4- (R=C6F5) show weakly bound ether molecules. Copyright
- Leszczynska, Kinga,Mix, Andreas,Berger, Raphael J. F.,Rummel, Britta,Neumann, Beate,Stammler, Hans-Georg,Jutzi, Peter
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supporting information; experimental part
p. 6843 - 6846
(2011/09/19)
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- Asymmetric cyanation of aldehydes, ketones, aldimines, and ketimines catalyzed by a versatile catalyst generated from cinchona alkaloid, achiral substituted 2,2′-biphenol and tetraisopropyl titanate
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Full investigation of cyanation of aldehydes, ketones, aldimines and ketimines with trimethylsilyl cyanide (TMSCN) or ethyl cyanoformate (CNCOOEt) as the cyanide source has been accomplished by employing an in situ generated catalyst from cinchona alkaloid, tetraisopropyl titanate [Ti(OiPr)4] and an achiral modified biphenol. With TMSCN as the cyanide source, good to excellent results have been achieved for the Strecker reaction of N-Ts (Ts=p-toluenesulfonyl) aldimines and ketimines (up to >99% yield and >99% ee) as well as for the cyanation of ketones (up to 99% yield and 98% ee). By using CNCOOEt as the alternative cyanide source, cyanation of aldehyde was accomplished and various enantioenriched cyanohydrin carbonates were prepared in up to 99% yield and 96% ee. Noteworthy, CNCOOEt was successfully employed for the first time in the asymmetric Strecker reaction of aldimines and ketimines, affording various a-amino nitriles with excellent yields and ee values (up to >99% yield and >99% ee). The merits of current protocol involved facile availability of ligand components, operational simplicity and mild reaction conditions, which made it convenient to prepare synthetically important chiral cyanohydrins and examino nitriles. Furthermore, control ex-periments and NMR analyses were performed to shed light on the catalyst structure. It is indicated that all the hydroxyl groups in cinchona alkaloid and biphenol complex with TiIV, forming the catalyst with the structure of (biphenoxide) Ti(OR*)(Oi'Pr). The absolute configuration adopted by biphenol 4 m in the catalyst was identified as S configuration according to the evidence from control experiments and NMR analyses. Moreover, the roles of the protonic additive ((iPrOH) and the tertiary amine in the cinchona alkaloid were studied in detail, and the real cyanide reagent in the catalytic cycle was found to be hydrogen cyanide (HCN). Finally, two plausible catalytic cycles were proposed to elucidate the reaction mechanisms.
- Wang, Jun,Wang, Wentao,Li, Wei,Hu, Xiaolei,Shen, Ke,Tan, Cheng,Liu, Xiaohua,Feng, Xiaoming
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scheme or table
p. 11642 - 11659
(2010/04/28)
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- Tellurium (Te) precursors for making phase change memory materials
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Tellurium (Te)-containing precursors, Te containing chalcogenide phase change materials are disclosed in the specification. A method of making Te containing chalcogenide phase change materials using ALD, CVD or cyclic CVD process is also disclosed in the specification in which at least one of the disclosed tellurium (Te)-containing precursors is introduced to the process.
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Page/Page column 6
(2009/01/20)
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- A convenient one-pot preparation of stable equivalents of cyclobutane-1,2-dione and cyclobutanetrione
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A very short, high-yielding, one-pot procedure has been developed for the preparation of half-protected cyclobutane-1,2-dione. This compound is much more stable than cyclobutane-1,2-dione itself and allowed further transformation to give diprotected cyclobutanetrione equivalents. Copyright Taylor & Francis Group, LLC.
- Deguest, Geoffrey,Bischoff, Laurent,Fruit, Corinne,Marsais, Francis
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p. 841 - 847
(2008/09/17)
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- Simple, rapid procedure for the synthesis of chloromethyl methyl ether and other chloro alkyl ethers
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Zinc(II) salts catalyze the reaction between acetals and acid halides to provide haloalkyl ethers in near-quantitative yield. Reactions from millimole to mole scale are typically complete in 1-4 h with 0.01 mol % catalyst. The solutions of haloalkyl ethers thus obtained can be utilized directly in reactions in which the presence of the ester byproduct does not interfere. Excess haloalkyl ether is destroyed on workup, thereby minimizing exposure to this class of carcinogenic compounds.
- Berliner, Martin A.,Belecki, Katherine
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p. 9618 - 9621
(2007/10/03)
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- Deoligomerization of siloxanes with dimethyl carbonate over solid-base catalysts
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Hexamethyldisiloxane and hexamethylcyclotrisiloxane were almost completely deoligomerized with dimethyl carbonate over alumina-supported potassium fluoride catalyst to form methoxytrimethylsilane (85% yield) and dimethoxydimethylsilane (94% yield), respec
- Okamoto,Miyazaki,Kado,Suzuki
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p. 1838 - 1839
(2007/10/03)
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- Intramolecular behaviors of anthryldicarbenic systems: Dibenzo[b,f]pentalene and, 1H,5H-dicyclobuta[de,kl]anthracene
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9,10-Bis[methoxy(trimethylsilyl)methyl]anthracenes (24), synthesized from 9,10-dilithioanthracene (26) and bromomethoxytrimethylsilylmethane (27, 2 equiv), decompose (550-650 °C/10-3 mmHg) carbenically to dibenzo[b,f]pentalene (28, >48%). 9,10-Anthryldicarbenes 39 or their equivalents convert to pentalene 28 rather than di-peri-cyclobutanthracenes 30 and 31, benzobiphenylene 32, or extended rearrangement products 33-38. Formation of 28 from 24 raises questions with respect to the behavior of 1,3,4,6-cycloheptatetraenyl-1-carbenes 49, 2,4,5,7-cyclooctatetraenylidene 51, 2,5,7-cyclooctatriene-1,4-diylidene 52, 1,2,4,5,7-cyclooctapentaene 53, and bicyclo[4.1.0]heptatrienyl-1-carbenes 54 and to carbon-skeleton and hydrogen rearrangements of anthryldicarbenes 39 and/or their equivalents at various temperatures. 1,5-Bis[methoxy(trimethylsilyl)methyl]anthracenes (25), prepared from 1,5-diiodoanthracene (63) and methoxytrimethylsilylmethylzinc bromide (57, 2 equiv) as catalyzed by PdCl2(PPh3)2, yield the di-peri-carbenic reaction product 1H,5H-dicyclobuta[de,kl]anthracene (30, >40%) on pyrolysis at 550-650 °C/10-3 mmHg. Proof of structure and various aspects of the mechanisms of formation of 30 are discussed.
- Kendall,Shechter
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p. 6643 - 6649
(2007/10/03)
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- Synthesis of acyclic α- and β-silyl sulfimides
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Conversion of acyclic α- and β-silyl Sulfides by their treatment with sodium salts of N-chlorosulfonamides into the corresponding previously unknown sulfimides is described. The process is accompanied by a competing reaction resulting in the formation of α- or β-silyl sulfoxides. β-Silyl sulfamide (9b) undergoes thermolysis to generate trimethylvinylsilane. The Royal Society of Chemistry 2000.
- Suslova, Elena N.,Kirpichenko, Svetlana V.,Albanov, Aleksandr I.,Shainyan, Bagrat A.
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p. 3140 - 3142
(2007/10/03)
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- The Conversion of Steroidal Ring B Lactones into Ortho Esters: Preparation of 7,7-Dimethoxy-6-oxaestra-1,3,5(10)-triene Derivatives
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17β-t-Butyldimethylsilyloxy-3-methoxy-6-oxaestra-1,3,5(10)-trien-7-one (1), prepared in three steps from 17β-hydroxy-3-methoxy-6-oxaestra-1,3,5(10),8-tetraen-7-one (5a), was converted via the corresponding phenolic acid into 1β-t-butyldimethylsilyloxy-5β-
- Bourke, David G.,Collins, David J.
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p. 1003 - 1018
(2007/10/03)
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- Substituent effects on the reactivity of the silicon-carbon double bond. Resonance, inductive, and steric effects of substituents at silicon on the reactivity of simple 1-methylsilenes
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The reactivities of a series of substituted 1-methylsilenes RMeSi=CH2 (R = H, methyl, ethyl, t-butyl, vinyl, ethynyl, phenyl, trimethylsilyl, and trimethylsilymethyl) in hydrocarbon solvents have been investigated by far- UV (193-nm) laser flash photolysis techniques, using the corresponding 1- methylsilacyclobutane derivatives as silene precursors. Each of these silacyclobutanes yields ethylene and the corresponding silene, which can be trapped as the alkoxysilane RSiMe2OR' cleanly upon 193- or 214-nm photolysis in solution in the presence of aliphatic alcohols. UV absorption spectra and absolute rate constants for reaction of the silenes with methanol, ethanol, and t-butyl alcohol have been determined in hexane solution at 23°C. The rate constants vary from a low 3 x 107 M-1 s-1 for reaction of 1- methyl-1-trimethylsilylsilene with t-BuOH to a high of 1 x 1010 M-1 s- 1 for reaction of 1-ethynyl-1-methylsilene with MeOH. In several cases, rate constants have been determined for addition of the deuterated alcohols, and for addition of methanol over the 0-55°C range. Invariably, small primary deuterium kinetic isotope effects and negative Arrhenius activation energies are observed. These characteristics are consistent with a mechanism involving reversible formation of a silene-alcohol complex which collapses to alkoxysilane by unimolecular proton transfer from oxygen to carbon. Silene reactivity increases with increasing resonance electron-donating and inductive electron-withdrawing ability of the substituents at silicon and is significantly affected by steric effects within this series of compounds. This is suggested to be due to a combination of effects on both the degree of electrophilicity at silicon (affecting the rate constants for formation and reversion of the complex) and nucleophilicity at carbon (affecting the partitioning of the complex between product and free reactants). Two 1- methyl-1-alkoxysilacyclobutanes were also investigated, but proved to be inert to 193-nm photolysis.
- Leigh, William J.,Boukherroub, Rabah,Kerst, Corinna
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p. 9504 - 9512
(2007/10/03)
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- Silicon-29 NMR spectra of trimethylsilylated alcohols
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29Si NMR spectra of trimethylsilyl (TMS) derivatives of 26 simple alcohols were measured under standardized conditions (i.e., in sufficiently diluted deuteriochloroform solutions). Due to association with the solvent the chemical shifts are in almost all cases larger than those reported earlier for different solutions. This observation is in agreement with the proposed mechanism of steric effects as being due to sterically controlled association with the solvent. The use of chloroform as a solvent enhances steric effects hut at the same time it can reduce small differences due to polar effects in closely related compounds. In the studied class of compounds the gross dependence of the chemical shift on polar effects is not substantially affected by the change of the solvent.
- Kvicalova, Magdalena,Cermak, Jan,Blechta, Vratislav,Schraml, Jan
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p. 816 - 820
(2007/10/03)
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- Far-UV laser flash photolysis in solution. A time-resolved spectroscopic study of the chemistry of 1,1-dimethyl-1,3-(1-sila)- butadiene
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Laser flash photolysis (193 nm) of 1,1-dimethyl-(1-sila)cyclobut-2-ene in hexane solution leads to the formation of a transient species (τ ～ 1.5 μs at 23°C) assigned to 1,1-dimethyl-1,3-(1-sila)butadiene on the basis of its UV absorption spectrum (λm
- Kerst, Corinna,Byloos, Martin,Leigh, William J.
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p. 975 - 982
(2007/10/03)
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- Mercury-sensitized photolysis of Me2SiH2 the disproportionation reactions of the Me2SiH radical
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Mercury-sensitized photolysis of Me2SiH2 yields in the primary step an Me2HSi radical and an H atom with a quantum yield of one. The Me2HSi radicals undergo a combination reaction [k(2)] as well as two kinds of disproportionate reactions leading to dimethylsilylene [k(3)] and 1-methylsilaethene [k(4)]. The following branching ratios have been determined: k(3)/[k(2) + k(3) + k(4)] = 0.64 ± 0.10 and k(4)/[k(2) + k(3) + k(4)] ≥ 0.007. For Me3Si radicals the branching ratio for disproportionation was also determined and a value of 0.063 was obtained.
- Kerst,Potzinger
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p. 1071 - 1078
(2007/10/03)
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- Silyl-nitrogen compounds, III: Synthesis and characterisation of pentasila-phospha and pentasila-arsa pentazenes
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Heteroatom incorporated pentazenes, pentakis(trimethylsisyl)-3-phospha-2-pentazene (Me3Si)2N-N-(SiMe3)2 and pentakis(trimethylsilyl)-3-arsa-2-pentazene (Me3Si)2N-N(SiMe3)-As=N-N-(SiMe3)2, have been isolated by the reaction of -dichlorophosphine (Me3Si)2N-N(SiMe3)-PCl2, with dilithium-bis(trimethylsilyl)hydrazine Li(SiMe3)N-N(SiMe3)Li and of dichloroarsine (SiMe3)2N-N(SiMe3)-AsCl2 with Li2N2(SiMe3)2, respectively.Both the compounds are reactive solids.The former thermolises slowly at 120 deg C (τ1/2=25 h) whereas the latter decomposes rapidly at 100 deg C and is sensitive to light.Phosphapentazene reacts with methanol both with addition at -P=N- as well as desilylation, wheres, arsapentazene undergoes cleavage reaction.Key words: pentasila-phospha-pentazene, pentasila-arsa-pentazene, synthesis, characterisaeion, reactivity.
- Vasisht, S. K.,Kaur, Tripat P.,Usha, K.,Kaushal, Jyotsna,Bandhu, Kavita
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p. 189 - 196
(2007/10/03)
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- New Syntheses of Methyleniminium Salts from Carbonyl Compounds and from α-Chloro Ethers; an Access to Vinylogous Viehe Salts
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Two methods for the synthesis of isolable methyleniminium salts and amidinium salts are presented.In the first case carbonyl compounds A are treated with a mixture of (dialkylamino)trimethylsilane (12) and chlorotrimethylsilane (13) or 12 and trimethylsilyl triflate (14) leading to the iminium chlorides F or iminium triflates G, respectively.With 12/13 the preparation of F is limited to non-enolizable aldehydes and dimethylformamide (10), while 12/14 enables the preparation of G, e.g. 23a-25a, 27a, also with ketones and with substituted amides.The second procedure is based on the treatment of α-chloro ethers L with 12.Both methods afford the Mannich reagent 16a in high yields.By reaction of the α-chloro ether 35 with 12 in diethyl ether the vinylogous Viehe salts 36a-c, e become available for the first time.The reaction pathways are discussed. - Key Words: Methyleniminium salts, preparation, mechanisms of formation / (Dialkylamino)trimethylsilanes / Ethers, α-chloro / Viehe salts, vinylogous
- Schroth, Werner,Jahn, Ullrich,Stroehl, Dieter
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p. 2013 - 2022
(2007/10/02)
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- Laser powered homogeneous decomposition of tetramethylcyclotetrasiloxane. A source for hydroxy(methyl)silylene
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Laser powered homogeneous co-pyrolysis of tetramethylcyclotetrasiloxane and 1,1-dimethyl-1-silacyclobutane affords products in a ratio consistent with the transient existence of hydroxy(methyl)silylene and its additiion to transient dimethylsilene.The sug
- Pola, J.,Cukanova, D.,Ponec, R.,Stanczyk, W.
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- Photochemistry of locally excited and intramolecular charge transfer states of a disilane bearing a cyclic arylethenyl electron acceptor substituent
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1-(p-cyanophenyl)-2-(pentamethyldisilanyl)cyclopentene (1) exhibits a fluorescence at λ > 400 nm, which strongly shifts to the red with increasing polarity of the solvent. The corresponding solvatochromic plot is indicative of an emissive, lowest energy charge-transfer (CT) state. Stern-Volmer quenching of the fluorescence by dilute methanol in pentane gives a linear plot with a unit intercept and a slope KQτct = 0.70. Quenching is accompanied by formation of (arylcyclopentenyl)dimethylsilane 7, the major product observed upon photolysis of 1 in the presence of methanol. This is evidenced by the linear double-reciprocal plot of quantum yields of 7 versus methanol concentration, which gives a kQτct value in agreement with fluorescence quenching. In addition to nucleophilic attack by methanol at the terminal trimethylsilyl group to give 7, two minor photoproducts, (arylcyclopentenyl)trimethylsilane 6 and a tricyclic product 8 are observed, which are attributable to silylene extrusion and to homolytic Si-Si bond cleavage, the latter process giving a silyl radical pair that cyclizes onto the ortho position of the aryl group with subsequent disproportionation. The Stern-Volmer plot of Φ°/Φ versus [MeOH] for 8 is curved, suggesting that both the locally excited (LE) and CT states are involved in the formation of this product. In contrast, quantum yields of 6 do not vary with alcohol concentration, consistent with the LE state as the origin of this product.
- Steinmetz, Mark G.,Yu, Changjun,Li, Lin
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p. 932 - 943
(2007/10/02)
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- Photochemical protodesilylation of 2-R3Si-1,3-dimethoxybenzenes. Direct observation of β-silyl-substituted cyclohexadienyl cations
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Irradiation (254 nm) of the title compounds 5 (R3Si = Me3Si, Ph2MeSi, and 4-XC6H4Me2Si with X = 4-MeO, 4-Me, H, 4-F, and 4-Cl) in 1,1,1,3,3,3-hexafluoroisopropyl alcohol (HFIP) results in q
- Lew, Calvin S. Q.,McClelland, Robert A.
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p. 11516 - 11520
(2007/10/02)
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- Donor-Acceptor Accelerated Norbornadiene Rearrangements
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The norbornadienone acetals 3 with a CO2Me, CONMe2 or CHO substituent at C-2 undergo rearrangement under very mild conditions; cycloheptatrienes are obtained for CO2Me and CONMe2 substituents and the furanone acetal 9 for the CHO substituent.The donor-acceptor acceleration is consistent with a formal 1,3-shift to a norcaradiene proceeding either via a zwitterionic intermediate or a concerted-forbidden path.Rearrangement via a biradical is not consistent with the slower rearrangement of 7-cyano-7-methoxy-2,3-bis(methoxycarbonyl)norbornadiene 16.The indene 19 racemises rapidly at a temperature 100 deg C below that required for 18 establishing that a donor and an acceptor (Me3SiO and CN) at a potential radical centre promote homolysis to a greater extent than two groups (two alkoxy groups).
- Bleasdale, Christine,Jones, David W.
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p. 2441 - 2452
(2007/10/02)
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- Cyanation of Allylic Carbonates and Acetates Using Trimethylsilyl Cyanide Catalyzed by Palladium Complex
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Allylic carbonates and acetates are cyanated with trimethylsilyl cyanide in the presence of a catalytic amount (5 mol percent based on the allylic substrates) od Pd(PPh3)4 or Pd(CO)(PPh3)3 in THF under reflux to afford β,γ-unsaturated nitriles in high yields.
- Tsuji, Yasushi,Yamada, Naoaki,Tanaka, Shinsuke
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- Generation and reactivities of methoxyphenylsilylene
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From the vacuum pyrolysis of 1,1-dimethoxy-1-phenyl -2,2,2-trimethyldisilane (I) in the presence of 2,3-dimethyl-1,3-butadiene, two major products, 1-methoxy-1-phenyl-3,4-dimethyl-1-silacyclopent-3-ene (II) and 1-phenyl-3,4-dimethyl-1-silacyclopent-3-ene
- Kwak, Young-Woo,Jeong, Ill-Hyeon,Ko, Jae-You,Boo, Bong Hyun
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p. 107 - 113
(2007/10/02)
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- N-NITROHYDRAZINES AND THEIR SALTS
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A method was developed for the synthesis of functionally substituted N-nitrohydrazines by nonacid nitration of the respective silylhydrazines.It was shown that the stability of these compounds increases with increase in the number of electronegative substituents.The first representative of N,N'-dinitrohydrazines, i.e., N,N'-dinitro-N,N'-diacetylhydrazine, was synthesized.Some of the obtained N-nitrohydrazines are characterized by dissociation with the formation of diazenes.The action of nucleophilic reagents on functionally N,N'-disubstituted N-methyl-N'-nitrohydrazines gave the salts of N-nitrohydrazines.
- Kalinin, A. V.,Apasov, E. T.,Ioffe, S. L.,Tartakovskii, V. A.
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p. 988 - 995
(2007/10/02)
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- A handy preparation of bis(trimethylsilyl)methylamine
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Reductive silylation of trimethylsilylcyanide provides a new and easy route to bis(trimethylsilyl)-methylamine, a versatile synthon.
- Picard, Jean-Paul,Grelier, Stephane,Dunogues, Jacques,Aizpurua, Jesus-Maria,Palomo, Claudio
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- Reaction Rates of Trimethylethoxysilane and Trimethylmethoxysilane in Alkaline Alcohol Solutions
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The kinetics of the reaction (CH3)3SiOC2H5 + CH3O- (CH3)3SiOCH3 + C2H5O- have been investigated in both directions by means of FTIR spectroscopy.To obtain k1, trimethylethoxysilane was reacted with methoxide in a metha
- Jaeglid, Ulf,Lindqvist, Oliver
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p. 887 - 891
(2007/10/02)
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- The Crystal Structure of Me3SiNPPh2CH2PPh2 and NMR Investigations on its Proposed Thermal Isomerization
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The crystal structure of Me3SiNPPh2CH2PPh2 (1) has been determined in order to obtain information about the ground state conformation in the solid, and about unusual steric effects which could give rise to conformational isomers.It was recently proposed t
- Schmidbaur, Hubert,Bowmaker, Graham A.,Kumberger, Otto,Mueller, Gerhard,Wolfsberger, Werner
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p. 476 - 482
(2007/10/02)
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