1073-06-9Relevant articles and documents
An intramolecular: Ortho -assisted activation of the silicon-hydrogen bond in arylsilanes: An experimental and theoretical study
Durka, Krzysztof,Urban, Mateusz,Czub, Maja,D?browski, Marek,Tomaszewski, Patryk,Luliński, Sergiusz
, p. 3705 - 3716 (2018/03/21)
An intramolecular activation of the Si-H bond in arylsilanes by selected ortho-assisting functional groups based on boron, carbon and phosphorus was investigated experimentally and by means of theoretical calculations. The major conclusion drawn is that the presence of a negatively charged oxygen atom in the functional group is essential for providing effective chelation to the silicon atom which in turn results in the increased hydridic character of a resulting five-coordinated species. In contrast, an intermolecular attack of hydroxide on the silicon atom in aryldimethylsilane results in the activation of the silicon-aryl bond. This increased reactivity of the Si-H bond in intramolecularly coordinated arylsilanes can be ascribed to a significant trans effect which operates in the preferred configuration. Hydrolytic cleavage of the Si-H bond results in dihydrogen elimination and the formation of various silicon heterocyclic systems such as benzosiloxaboroles, spiro-bis(siloxa)borinate, benzosilalactone and benzophosphoxasilole. In addition, intermolecular reduction of benzaldehydes with ortho-boronated arylsilane was observed whereas compounds bearing other reducible functional groups (COMe, COOEt, CN and NO2) were inert under comparable conditions. Specifically, an intramolecular reduction of the CN group in an ortho-silylated benzonitrile derivative was observed. The mechanism of Si-H bond activation was investigated by the DFT theoretical calculations. The calculations showed that the intramolecular coordination of the silicon atom effectively prevents the cleavage of the Si-aryl bond. Furthermore, the reaction is favored in anionic systems bearing COO-, B(OH)3- or CH2O- groups, while in the case of neutral functional groups such as PO(OEt)2 the process is much slower.
Preparation method of 3-bromofluorobenzene
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Paragraph 0069; 0070; 0071; 0072; 0073; 0074; 0075-0081, (2018/05/16)
The invention relates to the field of organic synthesis and in particular relates to a preparation method of 3-bromofluorobenzene. The preparation method of the 3-bromofluorobenzene, provided by the invention, comprises the following steps: 1) enabling o-fluoroaniline to react with sulfuric acid and a bromination reagent to prepare 2-fluoro-4-bromoaniline sulfate; 2) enabling the 2-fluoro-4-bromoaniline sulfate to react with sodium nitrite in the presence of a reducing agent and a catalyst under an acidic condition, so as to prepare the 3-bromofluorobenzene. The preparation method of the 3-bromofluorobenzene, provided by the invention, has the advantages of cheap and easy-to-obtain raw materials, simple technology, feasibility in post-treatment and high yield and is extremely applicable toindustrialization; acid water produced by diazo deamination reaction can be used repeatedly; after the acid water is repeatedly used for a plurality of times, enriched low-boiling-point solvents including isopropyl alcohol, acetone and the like in the acid water can be removed by distillation and then the acid water can be continually used repeatedly; in a diazo deamination process, hypophosphorous acid in a traditional technology is replaced with low-grade alcohol, so that water eutrophication caused by the fact that the phosphorus content in water exceeds the standard is avoided.
Fluorination of aromatic compounds with xenon difluoride in the presence of boron trifluoride etherate
Fedorov,Zubarev,Mortikov, V. Yu.,Rodinovskaya,Shestopalov
, p. 1049 - 1052 (2016/02/09)
Fluorination of benzene with the XeF2 - BF3?Et2O system in acetonitrile at low temperatures affords fluorobenzene in 18% yield, the conversion of benzene being 92%. The rest products are di-, tri-, tetra-, and polyphenyls with different fluorination pattern. Toluene and chloro- and bromobenzenes are fluorinated predominantly at the ortho and para positions. Fluorination of 4-nitroanisole affords 2-fluoro-4-nitroanisole in 73% yield.