- Structural Characterization of Hydro-, Chloro- and Fluoroorganylsilanes with Substituents of Varying Electron Withdrawing Character
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We report on the molecular structure of trimethylsilanes Si(CH3)3X in which the substituents X, namely (Z)-pentafluoropropen-1-yl, trifluoropropyn-1-yl, pentafluoroethyl, trifluorovinyl, vinyl, propyn-1-yl, di- and trichloromethyl, display electron withdrawing effects of varying strength. The lengths of the bonds between the silicon and the carbon atoms of X correlate with the hybridization of the respective orbitals and the steric demand of X rather than with the electron withdrawing capability. In case of chlorinated substituents dispersion effects seem to shorten the Si?C bond. Furthermore, a route for generating trifluoropropyn-1-yllithium from the cryogen 2,3,3,3-tetrafluoropropene (HFO-1234yf) and n-butyllithium is described. Tetrafluoropropen-1-yllithium is slowly formed at ?80 °C but even at this temperature spontaneous elimination of LiF occurs. Deprotonation of the formed 3,3,3-trifluoropropyne requires temperatures of above ?60 °C leading to trifluoropropyn-1-yllithium which appears as relatively stable at room temperature.
- Ke?ler, Mira,Porath, Sven,Stammler, Hans-Georg,Hoge, Berthold
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Read Online
- Generation and Applications of the Hydroxide Trihydrate Anion, [OH(OH2)3]?, Stabilized by a Weakly Coordinating Cation
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The reaction of a strongly basic phosphazene (Schwesinger base) with water afforded the corresponding metastable hydroxide trihydrate [OH(OH2)3]? salt. This is the first hydroxide solvate that is not in contact with a cation and furthermore one of rare known water-stabilized hydroxide anions. Thermolysis in vacuum results in the decomposition of the hydroxide salt and quantitative liberation of the free phosphazene base. This approach was used to synthesize the Schwesinger base from its hydrochloride salt after anion exchange in excellent yields of over 97 %. This deprotonation method can also be used for the phosphazene-base-catalyzed preparation of the Ruppert–Prakash reagent Me3SiCF3 using fluoroform (HCF3) as the trifluoromethyl building block and sodium hydroxide as the formal deprotonation agent.
- Weitkamp, Robin F.,Neumann, Beate,Stammler, Hans-Georg,Hoge, Berthold
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supporting information
p. 14633 - 14638
(2019/11/05)
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- NOVEL AROMATIC COMPOUNDS
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The present invention comprises novel aromatic molecules, which can be used in the treatment of pathological conditions, such as cancer, skin diseases, muscle disorders, and immune system-related disorders such as disorders of the hematopoietic system including the hematologic system in human and veterinary medicine.
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Page/Page column 108; 109
(2018/09/19)
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- Process for preparing polyfluoroalkylithium compounds
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The invention relates to a process for preparing polyfluoroalkyl-lithium compounds by deprotonation of polyfluoroalkyl compounds by means of lithium bases.
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Page/Page column 5
(2010/02/11)
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- The synthesis of tris(perfluoroalkyl)phosphines
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Tris(perfluoroalkyl)phosphines, of interest as turtable alternatives to the carbon monoxide ligand, can be synthesised by the nucleophile mediated reaction of perfluoroalkyltrimethylsilanes with triphenylphosphite; the method can be extended to diphosphines. The Royal Society of Chemistry 2005.
- Murphy-Jolly, Makeba B.,Lewis, Lesley C.,Caffyn, Andrew J. M.
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p. 4479 - 4480
(2007/10/03)
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- A simple procedure for nucleophilic perfluoroalkylation of organic and inorganic substrates
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The mixture RfI and tetrakis(dimethylamino)ethylene is used for the nucleophilic perfluoroalkylation. The reaction of chlorotrimethylsilane and RfI/tetrakis(dimethylamino)ethylene in diglyme results in the formation of RfSi(CH3)3 isolated in 55-81% yield. The interaction of this system with organic electrophiles such as benzoyl and benzensulphonyl chlorides, aliphatic and aromatic aldehydes and activated ketones leads to the formation of the corresponding condensation products in 24-62% yield.
- Petrov, Viacheslav A.
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p. 3267 - 3269
(2007/10/03)
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- Synthesis and Solvolysis of 7-(Perfluoroalkyl)-7-bicycloheptyl Derivatives
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Several α-(trifluoromethyl)- and α-(pentafluoroethyl)carbinols were synthesized by the addition of perfluoroalkylating agent (TMSCF3, TMSC2F5, and/or C2F5Li) to polycyclic ketones.An improved procedure for the preparation of α-(perfluoroalkyl)trimethylsilyl ethers from (perfluoroalkyl)trimethylsilanes and ketones was developed to facilitate the synthesis of the compounds of interest.All of the alcohols featured the bicycloheptyl skeleton or some analog of this structure containing double bonds or cyclopropyl groups.Sulfonate esters of the carbinols were prepared, and these sulfonates were solvolyzed in different solvents to examine the competition between destabilization of the carbocationic intermediates by perfluoroalkyl groups and stabilization by neighboring-group participation.The extent of the destabilization of the cations was gauged by the difference in rates of solvolysis of the α-hydrogen and α-(perfluoroalkyl) derivatives.The kα-H/kα-RF ratios ranged from 8 to ca. 1E4, and the extent of anchimeric assistance that occurred in each system influenced the difference in rates.The pentafluoroethyl group exerted a slightly smaller rate-retarding effect when compared to the trifluoromethyl group (kα-C2F5/kα-CF3 = 1.1-8.0).The products of the solvolysis reactions revealed a general trend of destabilization of both localized and delocalized cations by perfluoroalkyl groups.
- Nelson, Derek W.,O'Reilly, Neil J.,Speier, Jon,Gassman, Paul G.
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p. 8157 - 8171
(2007/10/02)
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- Preparation of Trifluoromethyl and Other Perfluoroalkyl Compounds with (Perfluoroalkyl)trimethylsilanes
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The preparation of a variety of novel perfluoroalkyl-substituted compounds in high yields using easily prepared (perfluoroalkyl)trimethylsilanes (1a - c) is described. (Trifluoromethyl)-, (pentafluoroethyl)-, and (heptafluoropropyl)trimethylsilane, 1a - c, respectively, react readily with carbonyl compounds, such as aldehydes and ketones, by a fluoride-initiated catalytic process.Fluoride-initiated addition of 1 to a carbonyl group generates an oxyanionic species which then further catalyzes the reaction.Even enolizable carbonyl compounds react cleanly under the reaction conditions.A study of the scope of the reactivity of 1a toward other carbonyl groups in esters, lactones and an acid chloride was also carried out.Thus 1a reacts cleanly with five- and six-membered ring lactones.However, unactivated esters do not react under the reaction conditions.The acid chloride reacts with 1a to give a mixture of products.
- Krishnamurti, Ramesh,Bellew, Donald R.,Prakash, G. K. Surya
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p. 984 - 989
(2007/10/02)
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- Process of the prparation of perfluoroalkyl compounds, and pentafluoroethyltrimethylsilane
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A process for the preparation of perfluoroalkyl compounds which comprises reacting a perfluoroalkyl-trimethylsilane of the general formula (CH3)3 Si-Cn F2n+1 (I), wherein the group Cn F2n+1 represents a perfluoroalkyl group having from 1 to 6 carbon atoms, with a carbonyl compound of the general formula F1 --CO--R2 (II), wherein R1 represents a hydrocarbon group or hydrogen and R2 represents a hydrocarbon group, a perfluoroalkyl group or a perfluoroaryl group, but wherein R1 and R2 together may also be part of an alicyclic ring system, in the presence of a salt-like fluoride--which is at least partially soluble in the reaction medium--as a catalyst to yield a silylether of the formula STR1 and isolating this compound or hydrolyzing it to yield an alcohol of the formula IV STR2 The invention also relates to pentafluoroethyl trimethylsilane (CH3)3 Si--CF2 CF3 and a process for the preparation of this compound.
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