- Production method of p-nitrobenzaldehyde
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The invention discloses a production method of p-nitrobenzaldehyde. The method comprises: step 1, adding p-nitrotoluene to a reactor, and performing heating to make p-nitrotoluene become a molten material liquid; step 2, dropwise adding bromine into the p-nitrotoluene feed liquid until the reaction is complete; step 3, performing cooling to 40-60 DEG C, and adding an organic solvent into the reactor until the product is completely dissolved; step 4, adding a carbonate aqueous solution into the reactor, performing heating to a reflux state, performing hydrolyzing, and performing reacting for 15-20 hours; and step 5, performing stirring, cooling, crystallizing, filtering, washing and drying to obtain a finished product. The method has the advantages of having simplicity and high efficiency,improving the utilization rate of the raw materials, and increasing the yield of the product, and is suitable for preparing p-nitrobenzaldehyde.
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Paragraph 0027-0103
(2020/08/22)
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- Visible-Light-Driven Oxidative Mono- and Dibromination of Benzylic sp 3 C-H Bonds with Potassium Bromide/Oxone at Room Temperature
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Benzylic sp 3 C-H bonds have been successfully brominated with potassium bromide by using Oxone as an oxidant in water/dichloromethane under visible light at room temperature. Toluene, ethylbenzene and other alkylbenzenes bearing an electron-withdrawing group, such as Br, Cl, COMe, CO 2 Et, CO 2 H, CN or NO 2, provide the corresponding benzylic monobromides in good to excellent yields in this reaction. Dibromides can also be produced in the presence of excess potassium bromide in a prolonged reaction time. Control of the illuminance of visible light (~500 lux) is crucial to achieving both high yield and high selectivity in these brominations. Mono- and difluorides can be conveniently prepared through nucleophilic substitutions of the benzylic bromides with potassium fluoride.
- Zhao, Mengdi,Li, Meiqi,Lu, Wenjun
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supporting information
p. 4933 - 4939
(2018/12/14)
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- Method for preparing benzyl bromide
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The invention provides a method for preparing benzyl bromide. The method comprises the following steps: by taking bromine released from a redox reaction between bromates and negative bromide ions in the presence of an acid as a bromine source in an organic solvent, carrying out a benzyl radical substitution reaction with a methylbenzene compound shown as a formula I under initiation of an initiator, thereby obtaining a corresponding benzyl bromide compound shown a formula II, wherein in the formula II, m represents the number of Br and is equal to 1 or 2; when m is equal to 1, the formula II shows a benzyl monobromo compound; and when m is equal to 2, the formula II shows a benzyl dibromo compound. The reaction is carried out in an organic solvent, the initiator is combined and used, the radical substitution reaction is high in selectivity and wide in substrate application range, the substituent group replacing methylbenzene may be an electron-withdrawing group or an electron-donating group and can give extremely high yield on strong electron-donating groups (such as methoxy group). Moreover, the method disclosed by the invention is also applicable to preparation of benzyl dibromo compounds, and the product yield is high.
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Paragraph 0079-0081
(2017/10/05)
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- A scalable procedure for light-induced benzylic brominations in continuous flow
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A continuous-flow protocol for the bromination of benzylic compounds with N-bromosuccinimide (NBS) is presented. The radical reactions were activated with a readily available household compact fluorescent lamp (CFL) using a simple flow reactor design based on transparent fluorinated ethylene polymer (FEP) tubing. All of the reactions were carried out using acetonitrile as the solvent, thus avoiding hazardous chlorinated solvents such as CCl4. For each substrate, only 1.05 equiv of NBS was necessary to fully transform the benzylic starting material into the corresponding bromide. The general character of the procedure was demonstrated by brominating a diverse set of 19 substrates containing different functional groups. Good to excellent isolated yields were obtained in all cases. The novel flow protocol can be readily scaled to multigram quantities by operating the reactor for longer time periods (throughput 30 mmol h-1), which is not easily possible in batch photochemical reactors. The bromination protocol can also be performed with equal efficiency in a larger flow reactor utilizing a more powerful lamp. For the bromination of phenylacetone as a model, a productivity of 180 mmol h -1 for the desired bromide was achieved.
- Cantillo, David,De Frutos, Oscar,Rincon, Juan A.,Mateos, Carlos,Oliver Kappe
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supporting information
p. 223 - 229
(2014/01/17)
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- Rasta resin-triphenylphosphine oxides and their use as recyclable heterogeneous reagent precursors in halogenation reactions
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Heterogeneous polymer-supported triphenylphosphine oxides based on the rasta resin architecture have been synthesized, and applied as reagent precursors in a wide range of halogenation reactions. The rasta resin-triphenylphosphine oxides were reacted with either oxalyl chloride or oxalyl bromide to form the corresponding halophosphonium salts, and these in turn were reacted with alcohols, aldehydes, aziridines and epoxides to form halogenated products in high yields after simple purification. The polymersupported triphenylphosphine oxides formed as a byproduct during these reactions could be recovered and reused numerous times with no appreciable decrease in reactivity.
- Xia, Xuanshu,Toy, Patrick H.
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supporting information
p. 1397 - 1405
(2014/07/22)
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- Microwave-assisted benzyl mono- and dibromination in diethyl carbonate as environmentally friendly alternative to radical bromination in carbon tetrachloride
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An environmentally friendly benzyl mono- and di-bromination synthetic procedure was developed that is superior to the classic carbon tetrachloride bromination procedure in both reaction time and isolated yield. This new reaction was performed in diethyl carbonate as reaction media using microwave instead of conventional heating. Both the solvent and the brominating reagent N-bromosuccinimide (prepared from succinimide obtained from the reaction mixture) are recyclable. Practically, the preparation of our target compounds was completed in less than two hours. The Royal Society of Chemistry.
- Pingali, Subramanya R. K.,Upadhyay, Sunil K.,Jursic, Branko S
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experimental part
p. 928 - 933
(2011/05/15)
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- Electrochemical method for the preparation of dibromomethyl, bis(bromomethyl), and bis(dibromomethyl) arenes
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Electrochemical bromination of alkyl aromatic compounds by two-phase electrolysis yields the corresponding α,α-dibrominated products. The reaction has been carried out in a single-compartment electrochemical cell using aqueous sodium bromide (40-50%), containing a catalytic amount of HBr as electrolyte, and chloroform, containing an alkyl aromatic compound, as the organic phase with a Pt plate as anode at 10-15C. Two-phase electrolysis results in high yields (70-90%) of dibromomethyl, bis(bromomethyl), and bis(dibromomethyl) arenes, depending upon the charge passed.
- Kulangiappar,Karthik,Kulandainathan, M. Anbu
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scheme or table
p. 2304 - 2309
(2009/12/06)
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- Visible-light-promoted Wohl-Ziegler functionalization of organic molecules with N-bromosuccinimide under solvent-free reaction conditions
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The visible-light-induced transformation of toluenes with N-bromosuccinimide (NBS) under solvent-free reaction conditions (SFRC) was studied. The reaction took place in spite of the very restricted molecular motion; toluenes could be regioselectively converted to benzyl bromides. Selective radical-chain reactions with NBS were carried out in liquid/liquid and in solid/solid systems; furthermore, reactions could be performed in the presence of air. The radical scavenger TEMPO (=2,2,6,6-tetramethylpiperidin-1- yloxy) completely suppressed the side-chain bromination of toluenes with NBS under SFRC. Electron-withdrawing groups decreased the reactivity of the toluenes, and the Hammett reaction constant ρ+ = -1.7 indicated involvement of polar radical intermediates with electrophilic character.
- Jereb, Marjan,Zupan, Marko,Stavber, Stojan
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experimental part
p. 555 - 566
(2009/09/06)
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- Side chain bromination of mono and dimethyl heteroaromatic and aromatic compounds by solid phase N-bromosuccinimide reaction without radical initiator under microwave
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A series of side chain mono and dibromo derivatives of mono and dimethyl heteroaromatic and aromatic compounds (1-17) were synthesized by one step solid phase N-bromosuccinimide (NBS) reaction without radical initiator by microwave irradiation. The benzylic mono and dibromo products were exclusively preferred except in the case of 6-methylpyridine amides (8 and 9) where nuclear and also side chain bromination resulted. Naphthyridine systems resulted improved yields. By this method, we also report the synthesis of 2-pivaloylaminopterin-6- carbaldehyde.
- Goswami, Shyamaprosad,Dey, Swapan,Jana, Subrata,Adak, Avijit Kumar
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p. 916 - 917
(2007/10/03)
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- Synthesis of bromoalkenes and alkylidene dibromides by reactions of carbonyl compounds with 2,4,4,6-tetrabromo-2,5-cyclohexadienone in the presence of triphenylphosphine
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Reactions of aliphatic and aromatic aldehydes with the 2,4,4,6-tetrabromo-2,5-cyclohexadienone-triphenylphosphine complex result in formation of the corresponding geminal dibromides. Ketones react with the same complex to give vinyl bromides.
- Matveeva,Feshin,Zefirov
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- Photothermal Side-Chain Bromination of Methyl-, Dimethyl-, and Trimethylbenzenes with N-Bromosuccinimide
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Tri- and dibromination of methyl-, dimethyl-, and trimethylbenzenes with N-bromosuccinimide were accomplished by photothermal reaction with a tungsten lamp in carbon tetrachloride or benzene. (Dibromomethyl)arenes and (tribromomethyl) derivatives were produced depending upon a solvent used and a substituent on the benzene ring.In the bromination of methylbenzenes without a substituent on the ortho-position, (tribromomethyl)benzenes were formed.On the other hand, ortho-substituted methylbenzenes gave (dibromomethyl)benzenes. α,β-Dibromo-1,2-diarylstilbenes were formed via the debrominative carbon-carbon coupling reaction of ...
- Mataka, Shuntaro,Liu, Guo-Bin,Sawada, Tsuyoshi,Kurisu, Masayoshi,Tashiro, Masashi
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p. 1113 - 1119
(2007/10/02)
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- 2,2-DIBROMO-2-(2,2,3,3-TETRAFLUOROPROPOXY)BENZO-1,3,2λ5-DIOXAPHOSPHOLE - A NEW BROMINATING REAGENT
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A new reagent 2,2-dibromo-2-(2,2,3,3-tetrafluoropropoxy)benzo-1,3,2λ5-dioxaphosphole is proposed for the synthesis of gem-dibromides from aldehydes.It was established that the concurrent reaction of chloral and propanal with this phosphole results in the exclusive formation of 1,1-dibromopropane; this favors the idea that the aldehyde acts as a nucleophilic particle in the rate-determining stage.
- Mironov, V. F.,Ofitserov, E. N.,Sinyashina, T. N.,Konovalova, I. V.
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p. 2228 - 2230
(2007/10/02)
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- Dihalomethylation of Nitroarenes via Vicarious Nucleophilic Substitution of Hydrogen with Trihalomethyl Carbanions
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Trichloro- and tribromomethyl carbanions generated by deprotonation of haloforms with potassium tert-butoxide in a THF-DMF mixture at ca. -70 deg C react with a variety of carbocyclic and heterocyclic nitroarenes according to the vicarious nucleophilic substitution scheme.The reaction provides an efficient and convenient way for the direct introduction of dihalomethyl substituents ortho and para to the nitro group, which in turn can be hydrolyzed to produce nitroaryl aldehydes.
- Makosza, M.,Owczarczyk, Z.
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p. 5094 - 5100
(2007/10/02)
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- Benzylic Bromination-Acetoxylation of Toluenes by Bromide Ion Catalyzed Thermal Decomposition of Peroxydisulfate in Acetic Acid in the Presence of Acetate Ions
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Side-chain bromination and acetoxylation of alkylaromatics by halide ion induced decomposition of potassium peroxydisulfate in acetic acid have been studied by product analysis techniques.Catalytic amounts of lithium bromide in the presence of sodium acetate were found effective in promoting benzylic bromination, followed by conversion to the corresponding benzyl acetates by reaction with acetate.The reaction is interpreted to take place by the redox and free-radical chain mechanism involving bromine atoms (ρ = -1.38 vs. ? + for substituted toluenes).In competiti ve experiments, benzyl and 4-nitrobenzyl acetates were found lees reactive than the corresponding toluenes in acetic acid with the couple S2O82-/Br- but more reactive in carbon tetrachloride with N-bromosuccinimide.
- Citterio, Attilio,Santi, Roberto,Pagani, Anselmo
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p. 4925 - 4927
(2007/10/02)
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