- Bromination of Phenols by Use of Benzyltrimethylammonium Tribromide
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The reaction of phenols with benzyltrimethylammonium tribromide in dichloromethane-methanol for 1 h at room temperature gave polybromophenols in good yields.
- Kajigaeshi, Shoji,Kakinami, Takaaki,Tokiyama, Hajime,Hirakawa, Takahiro,Okamoto, Tsuyoshi
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- Kinetics and mechanism of oxidation of aspirin by bromamine-T, N-bromosuccinimide, and N-bromophthalimide
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The kinetics of the oxidation of aspirin (ASP) by bromamine-T (BAT), N-bromo-succinimide (NBS), and N-bromophthalimide (NBP) has been studied in aqueous perchloric acid at 303 K. The oxidation reaction follows identical kinetics with first-order in [oxidant], fractional-order in [ASP], and inverse fractional-order in [H+]. Under identical experimental conditions the extent of oxidation with different oxidizing agents is in the order: NBS > BAT > NBP, The rate decreased with decreasing dielectric constant of the medium. The variation of ionic strength and the addition of the reaction products and halide ions had no significant effect on the reaction rate. The solvent isotope effect was studied using D2O. Kinetic parameters were evaluated by studying the reaction at different temperatures. The reaction products were identified by GC-MS. The proposed reaction mechanism and the derived rate law are consistent with the observed kinetic data. Formation and decomposition constants for ASP-oxidant complexes have been evaluated. Decarboxylation, bromination, and loss of acetic acid gave 2,4,6-tribromophenol.
- Ramachandrappa,Puttaswamy,Mayanna,Made Gowda
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- Electrophilic bromination in flow: A safe and sustainable alternative to the use of molecular bromine in batch
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Bromination reactions are crucial in today’s chemical industry since the versatility of the formed organobromides makes them suitable building blocks for numerous syntheses. However, the use of the toxic and highly reactive molecular bromine (Br2) makes these brominations very challenging and hazardous. We describe here a safe and straightforward protocol for bromination in continuous flow. The hazardous Br2 or KOBr is generated in situ by reacting an oxidant (NaOCl) with HBr or KBr, respectively, which is directly coupled to the bromination reaction and a quench of residual bromine. This protocol was demonstrated by polybrominating both alkenes and aromatic substrates in a wide variety of solvents, with yields ranging from 78% to 99%. The protocol can easily be adapted for the bromination of other substrates in an academic and industrial environment.
- Van Kerrebroeck, Reinout,Naert, Pieter,Heugebaert, Thomas S.A.,D’hooghe, Matthias,Stevens, Christian V.
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- Enthalpies of formation of 2,4,6-tribromophenol and of 2,4,6-tribromoaniline
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The standard (p0 = 101.325 kPa) molar enthalpies of formation at 298.15 K of crystalline 2,4,6-tribromophenol and of 2,4,6-tribromoaniline were determined by both solution-reaction calorimetry and by rotating-bomb calorimetry.The values from the two methods agreed to within the limits of experimental error.The standard molar enthalpies of sublimation at 298.15 K were measured by microcalorimetry. 2,4,6-Tribromophenol: ΔfH0m(cr) = -98.5+/-2.3 kJ*mol-1, ΔgcrH0m = 97.6+/-1.1 kJ*mol-1; 2,4,6-tribromoaniline: ΔfH0m(cr) = 57.9+/-2.4 kJ*mol-1, ΔgcrH0m = 101.1+/-1.1 kJ*mol-1.The derived standard molar enthalpies of formation of the gaseous compounds were compared with values estimated assuming that each group, when substituted into the benzene ring, produces a characteristic increment in the enthalpy of formation.
- Allot, Philip H.,Finch, Arthur,Pilcher, Geoffrey,Nunez, Lisardo,Barral, Luis
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- Studies directed toward total synthesis of rhodocomatulins: A regioselective synthesis of brominated hydroxyanthraquinones by anionic annulations
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In this work, brominated hydroxyanthraquinones, which are the core structural motif of naturally occurring bromorhodocomatulins, were successfully synthesized using Hauser annulation reaction as the key step. When brominated Michael acceptors (brominated p-quinone monoketals) and cyanophthalides or bromocyanophthalides (Hauser donors) were reacted under the annulation conditions, brominated anthraquinones were obtained with 81–87% yields for four examples. On acidic quenching, products were obtained as solid which were separated by filtration and purified by recrystallization in acetone. No chromatography was required.
- Sk, Md Raja,Chakraborty, Soumen,Mal, Dipakranjan
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- Benzylic oxidation by the GIF(IV) system
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Oxidation of ethylbenzene, diphenylmethane and benzylcyclopropane affords, in each case, the corresponding ketone as unique product. There is no detectable attack on the aromatic rings and only traces of phenol are formed from benzene. The oxidation of cumene affords acetophenone and 2-phenyl-2-hydroxypropane in nearly the same proportions as in a Gif(IV) oxidation of cumene hydroperoxide. An explanation is given.
- Barton,Halley,Ozbalik,Mehl
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- Oxidovanadium (V and IV) complexes incorporating coumarin based O^N^O ligand: Synthesis, structure and catalytic activities
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The tridentate ligand H2L1, [(E)-7-Hydroxy-8-[(2-hydroxy-phenylimino)-methyl]-4-methyl-chromen-2-one] has been used in the present work towards the synthesis of mononuclear oxidovanadium complexes. Three mononuclear complexes [VOL1(OMe)(MeOH)], 1; [VO(L1)(8-Hq)], 2 and [VO(L1)(1,10-phen)], 3 have been successfully synthesized with high yields by reacting [VO(acac)2] with H2L1 in 1:1 ratio in methanol under refluxing conditions where 8-hydroxyquinoline and 1,10-phenanthroline were used as co-ligands in the synthesis of complex 2 and 3. X-ray crystallographic studies reveal that in all the complexes synthesized in the present study, the ligand H2L1 binds as O^N^O coordinating ligand. The synthesized complexes were well characterized by using UV–Vis, IR, NMR and Mass spectral techniques. The physiochemical properties have been well interpreted by density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations. The synthesized complexes were established to show some distinctive properties e.g. oxidative bromination of aromatic aldehyde with high conversion rate and enhanced selectivity as well as high TON and TOF. The above properties were all well matched and demonstrated by using UV–visible and fluorescence as well as quenching studies. Complex 1 reacts with 3,5-DTBC catalytically in presence of molecular oxygen to generate corresponding ortho-benzoquinone.
- Majumder, Mitali,Krishna Rajak, Kajal
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- A scalable and green one-minute synthesis of substituted phenols
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A mild, green and highly efficient protocol was developed for the synthesis of substituted phenols via ipso-hydroxylation of arylboronic acids in ethanol. The method utilizes the combination of aqueous hydrogen peroxide as the oxidant and H2O2/HBr as the reagent under unprecedentedly simple and convenient conditions. A wide range of arylboronic acids were smoothly transformed into substituted phenols in very good to excellent yields without chromatographic purification. The reaction is scalable up to at least 5 grams at room temperature with one-minute reaction time and can be combined in a one-pot sequence with bromination and Pd-catalyzed cross-coupling to generate more diverse, highly substituted phenols.
- Elumalai, Vijayaragavan,Hansen, J?rn H.
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p. 40582 - 40587
(2020/11/18)
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- A convenient and efficient H2SO4-promoted regioselective monobromination of phenol derivatives using N-bromosuccinimide
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A convenient, rapid H2SO4-promoted regioselective monobromination reaction with N-bromosuccinimide was developed. The desired para-monobrominated or ortho-monobrominated products of phenol derivatives were obtained in good to excellent yields with high selectivity. Regioselective chlorination and iodination were also achieved in the presence of H2SO4 using N-chlorosuccinimide and N-iodosuccinimide, respectively.
- Wu, Yong-Qi,Lu, Hai-Jia,Zhao, Wen-Ting,Zhao, Hong-Yi,Lin, Zi-Yun,Zhang, Dong-Feng,Huang, Hai-Hong
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supporting information
p. 813 - 822
(2020/02/15)
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- Crystal structure and catalytic properties of a vanadium complex cis-[VO2(Him-py)(im-py)]2·3H2O
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The coordination behavior of Him-py (2-(1H-imidazol-2-yl)pyridine) toward vanadium has been explored. The six-coordinate complex, cis-[VO2(Him-py)(im-py)]2·3H2O (1), was synthesized by the coordination reaction of NH4VO3 and Him-py in the aqueous methanol solution, which was characterized by single-crystal X-ray technology. It belongs to the monoclinic space group P21/n with a = 8.0756(6), b = 19.3531(15), c = 11.4433(8), β = 106.905(2), V = 1711.2(2), and Z = 2. The crystal structure shows that the six-coordinate vanadium is bonded to two cis-oxido ligands and two bidentate ligands, Him-py and im-py. Interestingly, when crystals of 1 were immersed in H2O2, a peroxovanadium compound, (H2im-py)[OV(O2)2(Him-py)] (2), was obtained, which crystallizes in the orthorhombic space group Fdd2 with a = 22.600(2), b = 22.7259(13), c = 18.0146(11), V = 9252.4(12), and Z = 16, and consists of a seven-coordinate peroxovanadate(V) ion, one Him-py and one H2im-py ligand. Moreover, we also studied the catalytic activity of 1 in the oxidative bromination of phenol/aniline-like compounds towards mimicking bromoperoxidase reactivity.
- Sun, Meng,Zhang, Shaowei,Zhang, Jie,Xia, Wen,Chen, Jialiang,Yu, Xianyong
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p. 1899 - 1909
(2019/06/04)
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- Method for photocatalytic synthesis of polybrominated phenol compound in water phase
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The invention discloses a method for photocatalytic synthesis of a polybrominated phenol compound in a water phase, comprising the following steps: adding a catalytic amount of a radical initiator, aphenol derivative and low-toxic and cheap bromide salt and water into a reaction vessel, reacting at room temperature at 5 W power in a photocatalytic reactor for a certain period, extracting with ethyl acetate and then re-crystallizing to obtain a polybrominated phenol compound. The above radical initiator is eosin, azobisisobutanol, sodium persulfate, ammonium persulfate or potassium persulfate.The free radical initiator and the bromine salt are cheap and easily available, and the method is an ideal synthesis method of the polybrominated phenol compound. According to the method, low-toxicity bromine salt instead of liquid bromine is used to carry out a bromination reaction, unstable and explosive hydrogen peroxide is replaced with the cheap and easily-available free radical initiator, and an emerging photocatalytic method is used. The polybrominated phenol compound can be obtained in a high yield by only using a 5W power lamp for the reaction, the reaction selectivity is high, by-products are less, and the post-treatment is simple.
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Paragraph 0012-0018
(2019/08/30)
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- Crystal structure, NMR and catalytic properties of a bis-peroxovanadium [NH4][VO(O2)2(mpa)]·H2O
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By reacting NH4VO3 and mpa (mpa = 4-methoxypicolinamide) in the presence of H2O2, a bis-peroxovanadium [NH4][VO(O2)2(mpa)]·H2O (1) was obtained and characterized by X-ray single-crystal diffraction. Structural analyses demonstrate that 1 belongs to the monoclinic space group P21/c and consists of a bis-peroxovanadium [VO(O2)2(mpa)]?, one NH4+ counterion and one free lattice water. Adjacent [VO(O2)2(mpa)]? anions construct a 3D supramolecular framework through intra- and intermolecular hydrogen bonding interactions. The compositions of 1 in solution are investigated by using multinuclear (1H, 13C, and 51V) magnetic resonance, COSY, HSQC, HMBC, and variable temperature NMR in a 0.15 mol L?1 NaCl/D2O solution that mimics the physiological conditions. Comparing the results of single-crystal X-ray and NMR experiments, the VV ion in the undissociated [VO(O2)2(mpa)]? in solution displays a similar seven-coordinate distorted pentagonal bipyramidal geometry with the solid-state crystal. The catalytic activity of the 1 in the oxidative bromination for phenol/aniline-like compounds to mimic bromoperoxidases reactivity was also studied.
- Chen, Ping,Zhang, Shaowei,Zhang, Jie,Xia, Wen,Yu, Xianyong
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p. 239 - 250
(2019/02/01)
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- Graphene Oxide Promoted Oxidative Bromination of Anilines and Phenols in Water
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The mildly acidic and oxidative nature of graphene oxide, with its large surface area available for catalytic activity, has been explored in aromatic nuclear bromination chemistry for the first time. The versatile catalytic activity of graphene oxide (GO) has been used to selectively and rapidly brominate anilines and phenols in water. The best results were obtained at ambient temperatures using molecular bromine in a protocol promoted by oxidative bromination catalyzed by GO; these transformations proceeded with 100% atom economy with respect to bromine and high selectivities for the tribromoanilines and -phenols. Reduced graphene oxide (r-GO) was observed to form after the second recycle (third use) of GO. This technique is also effective with N-bromosuccinimide (NBS) as the brominating reagent. In the case of NBS, reactions were instantaneous and the GO displayed excellent recyclability without any loss of activity over several cycles.
- Ghorpade, Prashant Vasantrao,Pethsangave, Dattatray Appasha,Some, Surajit,Shankarling, Ganapati Subray
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p. 7388 - 7397
(2018/07/29)
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- 1,1,2,2-Tetrahydroperoxy-1,2-Diphenylethane: An efficient and high oxygen content oxidant in various oxidative reactions
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Several oxidative approaches namely thiocyanation of aromatic compounds, epoxidation of alkenes, amidation of aromatic aldehydes, epoxidation of α β-unsaturated ketones, oxidation of sulfides to sulfoxides and sulfones, bayer-villeger reaction, bromination and iodation of aniline and phenol derivatives oxidative esterification, oxidation of pyridines and oxidation of secondary, allylic and benzyllic alcohols were carried out using 1,1,2,2-Tetrahydroperoxy-1,2-Diphenylethane as the potential solid oxidant which can be stored for several months without any loss in its activity. All of the procedures were accomplished via mild reaction conditions and the products were afforded in high yields and short reaction times.
- Khosravi, Kaveh,Naserifar, Shirin
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supporting information
p. 6584 - 6592
(2018/10/05)
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- Practical, mild and efficient electrophilic bromination of phenols by a new I(iii)-based reagent: The PIDA-AlBr3 system
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A practical electrophilic bromination procedure for phenols and phenol-ethers was developed under efficient and very mild reaction conditions. A broad scope of arenes was investigated, including the benzimidazole and carbazole core as well as analgesics such as naproxen and paracetamol. The new I(iii)-based brominating reagent PhIOAcBr is operationally easy to prepare by mixing PIDA and AlBr3. Our DFT calculations suggest that this is likely the brominating active species, which is prepared in situ or isolated after centrifugation. Its stability at 4 °C after preparation was confirmed over a period of one month and no significant loss of its reactivity was observed. Additionally, the gram-scale bromination of 2-naphthol proceeds with excellent yields. Even for sterically hindered substrates, a moderately good reactivity is observed.
- Satkar, Yuvraj,Ramadoss, Velayudham,Nahide, Pradip D.,García-Medina, Ernesto,Juárez-Ornelas, Kevin A.,Alonso-Castro, Angel J.,Chávez-Rivera, Ruben,Jiménez-Halla, J. Oscar C.,Solorio-Alvarado, César R.
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p. 17806 - 17812
(2018/05/28)
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- Synthesis of new oxido-vanadium complexes: Catalytic properties and cytotoxicity
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Reaction of 2,3-dihydroxy benzaldehyde with 2-({2-amino phenyl}diazenyl)phenol afforded the ligand 3-(2-(2-hydroxyphenyl)diazenyl)- 4-alkylphenyliminomethyl)benzene-1,2-diol. Reaction of H2L with VOSO4. 5H2O gave the oxido-vanadium(IV) complexes [(L)VO], which exhibited a quasi-reversible oxidative cyclic voltammetric response in a V(IV)/V(V) oxidative process. The complexes act as catalysts in the oxidation of organic thioethers and bromination of phenol. Their cytotoxic properties were examined for three cancer cell lines.
- Das, Uttam,Pattanayak, Poulami,Santra, Manas Kumar,Chattopadhyay, Surajit
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- A bromo-capped diruthenium(i,i) N-heterocyclic carbene compound for in situ bromine generation with NBS: Catalytic olefin aziridination reactions
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A bromo-capped metal-metal bonded diruthenium(i,i) complex Ru2(CO)4(PIN)2Br2 (1) (PIN = 1-isopropyl-3-(5,7-dimethyl-1,8-naphthyrid-2-yl)imidazol-2-ylidene) generates bromine with N-bromosuccinimide (NBS) at room temperature. Cycloalkene and stilbene are readily brominated by stoichiometric reactions with 1 and NBS. An analysis of the dibrominated products suggests the formation of cyclic bromonium intermediates indicating in situ Br2 generation. Complex 2, an iodide analogue of 1, is also synthesized. The reaction of 2 with N-iodosuccinimide releases I2, which is confirmed by the starch-iodine test. The catalytic utility of 1 is examined for the bromination of phenol. Catalyst 1, in combination with NBS and base, exhibits regioselectivity towards monobrominated products. Furthermore, efficient olefin aziridination is demonstrated utilizing catalyst 1 in the presence of NBS, K2CO3 and TsNH2.
- Sengupta, Gargi,Pandey, Pragati,De, Subhabrata,Ramapanicker, Ramesh,Bera, Jitendra K.
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supporting information
p. 11917 - 11924
(2018/09/10)
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- Reductive Bis-addition of Aromatic Aldehydes to α,β-Unsaturated Esters via the Use of Sm/Cu(I) in Air: A Route to the Construction of Furofuran Lignans
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The novel bis-addition of benzaldehydes to acrylates or maleates was achieved by the direct use of samarium metal with the assistance of CuI under mild conditions under dry air, and the useful 2-hydroxylalkyl-γ-butyrolactons and lignan derivatives were thus constructed with high efficiency. The key factors that influence the reaction efficiency were investigated. The use of potassium iodide and molecular sieves as additives can improve the reaction efficiency remarkably.
- Liu, Yongjun,Tian, Guang,Li, Jingjing,Qi, Yan,Wen, Yonghong,Du, Feng
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p. 5932 - 5939
(2017/06/07)
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- Regioselective monobromination of aromatics via a halogen bond acceptor-donor interaction of catalytic thioamide and N-bromosuccinimide
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Regioselective monobromination of various aromatics was achieved at room temperature using N-bromosuccinimide and 5 mol% of thioamides in acetonitrile. With thiourea as catalyst, activated aromatics, such as anisole, acetanilide, benzamide and phenol analogues containing electron donating or withdrawing groups, were brominated with high regioselectivity. Room temperature brominations of weakly activated aromatics and deactivated 9-fluorenone were accomplished by 5 mol% thioacetamide, higher substrates concentrations and longer reaction times. A backbonding of the bromine lone pairs with the π*of C[dbnd]S group and a halogen bond between the halogen bond donor bromine and the halogen bond acceptor sulfur of the thioamide are thought to be the principal interactions and cause of N-bromosuccinimide activation.
- Bovonsombat, Pakorn,Teecomegaet, Pattaradra,Kulvaranon, Panisanun,Pandey, Aditi,Chobtumskul, Kittithorn,Tungsirisurp, Sireethorn,Sophanpanichkul, Punyanuch,Losuwanakul, Satreerat,Soimaneewan, Dechathon,Kanjanwongpaisan, Patcharida,Siricharoensang, Pornpawit,Choosakoonkriang, Sirirat
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p. 6564 - 6572
(2017/10/17)
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- Preparation method of flame retardant for inflammable hazardous chemical plastic products
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The invention discloses a preparation method of a flame retardant for inflammable hazardous chemical plastic products. The method includes the steps of: 1) in an aliphatic-series halogenated solvent, dissolving phenol, performing a dropwise-adding reaction under stirring with bromine, slowly increasing the temperature until the boiling range of the solvent, and performing reflux to prepare a dibromo (tribromo) phenol aliphatic-series halogenated solution; 2) slowly dropwise adding a newly distilled industrial product phosphorus oxychloride, and slowly dropwise adding diluted triethylamine into the reaction bottle, and then slowly increasing the temperature so as to perform a reaction to the solvent at boiling temperature; 3) maintaining stable reflux to prepare tri(2,4-dibromophenyl) phosphate or tri(2,4,6-tribromophenyl) phosphate; and 4) water-washing and re-crystallizing the product to obtain the flame retardant. The flame retardant is toxic-free, is low in melt point, has good thermostability and compatibility, is good in flame retarding effect, and can be widely used in engineering plastics and alloys, such as nitro-cotton, celluloid and the like.
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Paragraph 0015; 0092-0097
(2017/09/28)
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- Method for preparing baicalein
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The invention relates to a method for preparing anti-virus and anti-bacterial inflammatory medicine baicalein. According to the method, phenol serves as a starting material, and a key chalcone intermediate is prepared through bromination, methoxy substitution, Friedel-crafts acylation and aldol condensation; the key intermediate is subjected to oxidative cyclisation and methyl removal reaction, and high-purity baicalein can be prepared. According to the new method, adopted raw reagents are cheap and easy to obtain, the number of synthesis steps is small, reaction operation is easy and convenient, production control is easy, the product yield is high, purity is good, and the method is suitable for production and application of baicalein.
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Paragraph 007; 008; 0027
(2016/10/09)
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- Green process development for the preparation of 2,6-dibromo-4-nitroaniline from 4-nitroaniline using bromide-bromate salts in an aqueous acidic medium
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An organic solvent-free process for the preparation of 2,6-dibromo-4-nitroaniline, (an important intermediate in the synthesis of azo disperse dyes) from 4-nitroaniline using 2:1 bromide-bromate salts under an aqueous acidic medium at ambient conditions has been developed. The 2:1 bromide-bromate couple could be obtained by mixing pure NaBr/NaBrO3 salts or by adjusting the 5:1 mole ratio of NaBr/NaBrO3 (obtained in an aqueous solution as an intermediate from the bromine manufacture industry by a cold process) to 2:1 by the addition of a suitable oxidant. After completion of the reaction the product was purified by simple filtration and washing with water. The aqueous acidic filtrate was recycled up to five times without loss of purity and yield of the product. The method was extended to other aromatic substrates.
- Pappula, Venkatanarayana,Adimurthy, Subbarayappa
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p. 90184 - 90187
(2016/10/07)
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- A quick, mild and efficient bromination using a CFBSA/KBr system
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Bromination is a fundamental transformation in organic chemistry and brominated compounds as building blocks are of paramount importance in organic synthesis. In our study, we have developed an efficient method of bromination by using a CFBSA/KBr system at room temperature in a short reaction time. Notably, this approach has been proven to be applicable to a range of substrates including 1,3-diketones and β-keto esters, phenols, aromatic amines and heteroarenes with good to excellent yields.
- Jiang, Pan-Pan,Yang, Xian-Jin
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p. 90031 - 90034
(2016/10/09)
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- A preparation gas bromine 2, 4, 6-plasma device and process thereof
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The invention discloses a device for preparing 2,4,6-tribromophenol by using gas bromide and a technology thereof. The device comprises a chemical reaction kettle, wherein the chemical reaction kettle is communicated with a bromine vaporizing kettle through an after-vaporization bromine pipeline; a jacket is arranged outside the bromine vaporizing kettle and communicated with a steam pipeline; one end of the after-vaporization bromine pipeline is communicated with the upper end of the bromine vaporizing kettle; the other end of the after-vaporization bromine pipeline is inserted to the bottom of the chemical reaction kettle; the chemical reaction kettle is also communicated with a solid phenol pool through a pipeline; a pump is arranged on the pipeline; and the solid phenol pool is also communicated with the steam pipeline. The liquid bromide is heated and vaporized by steam to realize bromination in the reaction between phenol and ethyl alcohol; the bromine is effectively purified after being vaporized; impurities in the liquid bromide are removed in the vaporization process of the liquid bromide, and the high purity of the reacted 2,4,6-tribromophenol product is ensured.
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Paragraph 0022-0029
(2017/02/24)
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- Vanadium bromoperoxidase (VBrPO) mimics: Synthesis, structure and a comparative account of the catalytic activity of newly synthesized oxidovanadium and oxido-peroxidovanadium complexes
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The bioinspired catalytic activities of two newly synthesised vanadium(iv)dioxido (complex 1) and vanadium(v) oxido-peroxido (complex 2) complexes with the neutral tridentate benzimidazole ligand, 2,6-di-(1H-benzo[d]imidazol-2-yl)pyridine (Byim) have been established. The bromoperoxidase activities of these complexes have been established through the activation of C-H bonds of substrates like phenol, o-cresol and p-cresol. The products, characterized by GC analysis shows that good conversions have been achieved. Considering the catalytic efficiency of the complexes, complex 2, with one in-built peroxido group is found to be more potent than complex 1. The catalytic cycles of both the complexes have been established from experimental results.
- Palmajumder, Eshita,Patra, Swarup,Drew, Michael G. B.,Mukherjea, Kalyan K.
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p. 8696 - 8703
(2016/10/13)
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- Rapid and total bromination of aromatic compounds using TsNBr2 without any catalyst
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N,N-Dibromo-p-toluenesulfonamide (TsNBr2) has been found to be a new reagent for bromination of aromatic compounds. The reaction is extremely fast and goes into completion instantaneously at ambient temperature to produce exclusively the corresponding polybrominated product. This procedure is applicable to various phenols, anisole, and anilines to give corresponding polybrominated compound as a single product in excellent yield.
- Saikia, Indranirekha,Chakraborty, Pranita,Sarma, Manas Jyoti,Goswami, Mridusmita,Phukan, Prodeep
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p. 211 - 217
(2015/10/29)
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- Synthesis, structural studies and catalytic activity of dioxidomolybdenum(VI) complexes with aroylhydrazones of naphthol-derivative
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Reaction of the salicylhydrazone of 2-hydroxy-1-naphthaldehyde (H 2L1), anthranylhydrazone of 2-hydroxy-1-naphthaldehyde (H2L2), benzoylhydrazone of 2-hydroxy-1-acetonaphthone (H2L3) and anthranylhydrazone of 2-hydroxy-1- acetonaphthone (H2L4; general abbreviation H2L) with [MoO2(acac)2] afforded a series of 5- and 6- coordinate Mo(VI) complexes of the type [MoO2L1-2(ROH)] [where R = C2H5 (1) and CH3 (2)], and [MoO 2L3-4] (3 and 4). The substrate binding capacity of 1 has been demonstrated by the formation of one mononuclear mixed-ligand dioxidomolybdenum complex [MoO2L1(Q)] {where Q = γ-picoline (1a)}. Molecular structure of all the complexes (1, 1a, 2, 3 and 4) is determined by X-ray crystallography, demonstrating the dibasic tridentate behavior of ligands. All the complexes show two irreversible reductive responses within the potential window -0.73 to -1.08 V, due to Mo VI/MoV and MoV/MoIV processes. Catalytic potential of these complexes was tested for the oxidation of benzoin using 30% aqueous H2O2 as an oxidant in methanol. At least four reaction products, benzoic acid, benzaldehyde-dimethylacetal, methyl benzoate and benzil were obtained with the 95-99% conversion under optimized reaction conditions. Oxidative bromination of salicylaldehyde, a functional mimic of haloperoxidases, in aqueous H2O2/KBr in the presence of HClO4 at room temperature has also been carried out successfully.
- Pasayat, Sagarika,Dash, Subhashree P.,Roy, Satabdi,Dinda, Rupam,Dhaka, Sarita,Maurya, Mannar R.,Kaminsky, Werner,Patil, Yogesh P.,Nethaji
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- Polymer-grafted and neat vanadium(V) complexes as functional mimics of haloperoxidases
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The monobasic tridentate ONN donor ligand 1-(2-pyridylazo)-2-naphthol [Hpan (I)] reacts with [VIVO(acac)2] in dry methanol to yield the oxidovanadium(IV) complex [VIVO(acac)(pan)] (1). The dioxidovanadium(V) complex [{VVO(pan)}2(μ-O) 2] (2) is obtained by aerial oxidation of 1 in methanol. Complex 2 can also be prepared directly by reacting [VIVO(acac)2] with I followed by aerial oxidation in methanol. Treatment of 1 or 2 in methanol with H2O2 yields the oxidomonoperoxidovanadium(V) complex [VVO(O2)(pan)(MeOH)] (3). Reaction of imidazolomethylpolystyrene cross-linked with 5% divinylbenzene (PS-im) with 2 in DMF resulted in the formation of the polymer-grafted dioxidovanadium(V) complex PS-im[VVO2(pan)] (4). All these complexes are characterized by various spectroscopic techniques (IR, electronic, NMR ( 1H and 51V) and electron paramagnetic resonance (EPR)), thermal, field-emission scanning electron micrographs (FE-SEM) as well as energy dispersive X-ray (EDX) studies. The crystal and molecular structure of 3 has been determined, confirming the ONN binding mode of I. The polymer-grafted complex 4 has been used for the oxidative bromination of styrene, salicylaldehyde and trans-stilbene. Various parameters, such as amounts of catalyst, oxidant (aqueous 30% H2O2), KBr and aqueous 70% HClO4 have been optimized to obtain the maximum oxidative bromination of the substrates. Under the optimized reaction conditions, styrene gave a maximum of 99% conversion after 2 h of reaction, with the main products having a selectivity order of: 1-phenylethane-1,2-diol (75%) > 2-bromo-1- phenylethane-1-ol (20%) > 1,2-dibromo-1-phenylethane (1.2%). With nearly same conversion in same time, the oxidative bromination of salicylaldehyde gave three products with the selectivity order: 5-bromosalicylaldehyde > 2,4,6-tribromophenol > 3,5-dibromosalicylaldehyde. A maximum of 91% conversion of trans-stilbene has been obtained in 2 h of reaction time, where selectivity of the obtained reaction products varied in the order: 2,3-diphenyloxirane (trans-stilbene oxide) > 1,2-dibromo-1,2-diphenylethane > 2-bromo-1,2-diphenylethanol. The catalytic activity of the non-polymer grafted complex 2 is lower than that of the polymer-grafted one. In addition, the recycling ability of the grafted complex makes it better over the neat complex.
- Maurya, Mannar R.,Chaudhary, Nikita,Avecilla, Fernando
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p. 436 - 448
(2013/11/19)
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- Base-promoted protodeboronation of 2,6-disubstituted arylboronic acids
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Facile based promoted deboronation of electron-deficient arylboronate esters was observed for arylboronates containing two ortho electron-withdrawing group (EWG) substituents. Among 30 representative boronates, only the diortho-substituted species underwe
- Lozada, Jerome,Liu, Zhibo,Perrin, David M.
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p. 5365 - 5368
(2014/06/23)
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- Copper(II)-catalyzed aromatization followed by bromination of cyclohexenones leading to phenols and bromophenols
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Conversion of substituted cyclohexenones into the corresponding phenols can be achieved using copper acetate as the catalyst in the presence of LiBr and CF3COOH under oxygen. With the use of excess LiBr, electrophilic aromatic bromination afforded the corresponding bromophenol under similar catalytic conditions. Copyright
- Tong, Hung-Chun,Reddy, K. Rajender,Liu, Shiuh-Tzung
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p. 3256 - 3261
(2014/06/09)
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- Efficient method for demethylation of aryl methyl ether using aliquat-336
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A rapid method for selective cleavage of aryl methylethers can be achieved in the presence of a protic acid and a catalytic amount of phase-transfer catalyst (Aliquat-336). Aliquat-336 accelerates the rate of reaction and affords the corresponding phenols in excellent to good yields on a wide variety of substrates. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications for the following free supplemental resource(s): Full experimental and spectral details.]
- Waghmode, Suresh B.,Mahale, Ganesh,Patil, Viraj P.,Renalson, Kartik,Singh, Dharmendra
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supporting information
p. 3272 - 3280
(2013/10/01)
-
- Synthesis, structural characterization, VHPO mimicking peroxidative bromination and DNA nuclease activity of oxovanadium(v) complexes
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The two novel oxovanadium(v) complexes [VO(PyDC)(BHA)] (1) [PyDC = pyridine-2,6-dicarboxylate, BHA = benzohydroxamate] and [VO(PyDC)(BPHA)] (2) [BPHA = benzophenyl hydroxamate] were synthesized by successive addition of a methanolic solution of H2PyDC and the corresponding hydroxamic acid ligand to the aqueous solution of ammonium metavanadate (NH4VO 3). The hydroxamic acid ligands were characterized by elemental analysis, IR, UV-vis and NMR studies whereas the complexes were characterized by IR, UV-vis, CHN, molar conductance, magnetic moment, mass and NMR spectroscopic methods. The structures of the complexes were determined by single crystal X-ray crystallography. The structures of both complexes reveal that vanadium(v) has distorted octahedral geometry. The bromoperoxidase activities of these complexes have been demonstrated through the activation of C-H bonds of phenol, o-cresol and p-cresol. The catalytic products have been characterized by GC-MS analysis which shows that good conversions have been achieved. So far as the catalytic efficiency of the complexes are concerned complex 2 is found to be superior to complex 1. Both the complexes were tested for DNA nuclease activity with pUC19 plasmid DNA. The results show that both of them exhibited nuclease activity against pUC19 circular plasmid DNA. The complexes produced both nicked coils and linear forms. In this case also it is observed that complex 2 shows better nuclease activity than complex 1.
- Patra, Swarup,Chatterjee, Suparna,Si, Tapan Kr.,Mukherjea, Kalyan K.
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p. 13425 - 13435
(2013/09/23)
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- Vanadate-dependent bromoperoxidases from Ascophyllum nodosum in the synthesis of brominated phenols and pyrroles
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Bromoperoxidases from the brown alga Ascophyllum nodosum, abbreviated as VBrPO(AnI) and VBrPO(AnII), show 41% sequence homology and differ by a factor of two in the percentage of α-helical secondary structures. Protein monomers organize into homodimers for VBrPO(AnI) and hexamers for VBrPO(AnII). Bromoperoxidase II binds hydrogen peroxide and bromide by approximately one order of magnitude stronger than VBrPO(AnI). In oxidation catalysis, bromoperoxidases I and II turn over hydrogen peroxide and bromide similarly fast, yielding in morpholine-4-ethanesulfonic acid (MES)-buffered aqueous tert-butanol (pH 6.2) molecular bromine as reagent for electrophilic hydrocarbon bromination. Alternative compounds, such as tribromide and hypobromous acid are not sufficiently electrophilic for being directly involved in carbon-bromine bond formation. A decrease in electrophilicity from bromine via hypobromous acid to tribromide correlates in a frontier molecular orbital (FMO) analysis with larger energy gaps between the π-type HOMO of, for example, an alkene and the σ*Br,X-type LUMO of the bromination reagent. By using this approach, the reactivity of substrates and selectivity for carbon-bromine bond formation in reactions mediated by vanadate-dependent bromoperoxidases become predictable, as exemplified by the synthesis of bromopyrroles occurring naturally in marine sponges of the genera Agelas, Acanthella, and Axinella. The Royal Society of Chemistry.
- Wischang, Diana,Radlow, Madlen,Hartung, Jens
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p. 11926 - 11940
(2013/09/02)
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- Bromination of phenols in bromoperoxidase-catalyzed oxidations
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Phenol and ortho-substituted derivatives furnish products of selective para-bromination, if treated with sodium bromide, hydrogen peroxide, and the vanadate(V)-dependent bromoperoxidase I from the brown alga Ascophyllum nodosum. Relative rates of bromination in morpholine-4-ethane sulfonic acid (MES)-buffered aqueous tert-butanol (pH 6.2) increase by a factor 32, as the ortho-substituent in a phenol changes from F via Cl, OCH3, C(CH 3)3, and H to CH3. The polar effect in phenol bromination by the enzymatic method, according to a Hammett-correlation (ρ=-3), compares to reactivity of molecular bromine under identical conditions (ρ=-2). Hypobromous acid is not able to electrophilically substitute bromine for hydrogen at pH 6.2 in aqueous tert-butanol. The tribromide anion behaves in MES-buffered aqueous tert-butanol as electrophile (ρ～-3), showing a similar polar effect in phenol bromination as molecular bromine.
- Wischang, Diana,Hartung, Jens
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supporting information
p. 9456 - 9463
(2012/11/07)
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- Regioselective bromination and iodination of aromatic substrates promoted by trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane
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Selective and efficient bromination and iodination of aromatic compounds by ammonium bromide and ammonium iodide, respectively, under promotion of trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane have been explored. Mild reaction conditions, high selectivity and yield, and high reaction rate are some of the major advantages of this synthetic method.
- Azarifar, Davood,Khosravi, Kaveh,Najminejad, Zohreh,Soleimani, Khadijeh
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experimental part
p. 321 - 326
(2012/08/14)
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- A Green protocol for the bromination and iodination of the aromatic compounds using H5IO6/NaBr and H5IO 6/NaI in the water
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Bromination and iodination of the aromatic compounds have efficiently been carried out at room temperature and 70 °C, respectively, in short reaction times using orthoperiodic acid/sodium bromide (1:2) and orthoperiodic acid/sodium iodide (1:2) in water to prepare the corresponding halo compounds with excellent yields.
- Yousefi-Seyf, Jaber,Tajeian, Kazem,Kolvari, Eskandar,Koukabi, Nadiya,Khazaei, Ardeshir,Zolfigol, Mohammad Ali
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p. 2619 - 2622
(2012/10/29)
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- Green, mild and efficient bromination of aromatic compounds by HBr promoted by trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane in water as a solvent
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A combination of HBr and trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane as a new and powerful oxidant was found effective for facile bromination of different aromatic compounds at room temperature in water as a green solvent. Mild reaction conditions, high selectivity and yield, high reaction rate and non-toxicity are some of the major advantages of this synthetic protocol.
- Khosravi, Kaveh,Kazemi, Samira
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experimental part
p. 387 - 390
(2012/05/20)
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- Synthesis, characterization, catalytic and antiamoebic activity of vanadium complexes of binucleating bis(dibasic tridentate ONS donor) ligand systems
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[VIVO(acac)2] (acac = acetylacetonate) was treated with ligands CH2(H2L)2 in methanol heated at reflux to yield two neutral binuclear VIV complexes with the formula [CH2{VIVOL(H2O)}2], namely, 1 and 2. Ligands CH2(H2L)2 I and II were derived from 5,5'-methylenebis(salicylaldehyde) and S-benzyldithiocarbazate [CH 2(H2sal-sbdt)2, I] or S-methyldithiocarbazate [CH2(H2sal-smdt)2, II]. Aerial oxidation of 1 and 2 in the presence of KOH or CsOH·H2O resulted in the formation of dioxidovanadium(V) complexes, K2[CH2{V VO2(sal-sbdt)}2]·2H2O (3), Cs2[CH2{VVO2(sal-sbdt)} 2]·2H2O (4), K2[CH2{V VO2(sal-smdt)}2]·2H2O (5) and Cs2[CH2{VVO2(sal-smdt)} 2]·2H2O (6). The compounds were characterized in the solid state and in solution, namely, by spectroscopic techniques (IR, UV/Vis, EPR, 1H, 13C and 51V NMR spectroscopy). It is demonstrated that the VVO2 complexes 3-6 are efficient and selective towards the oxidative bromination by H2O 2 of styrene to yield 1,2-dibromo-1-phenylethane, 1-phenylethane-1,2-diol and 2-bromo-1-phenylethane-1-ol, and of salicylaldehyde to yield 5-bromosalicylaldehyde, 3,5-dibromosalicylaldehyde and 2,4,6-tribromophenol; they therefore act as functional models of vanadium-dependent haloperoxidases. It is also shown that Cs2[CH 2{VVO2(sal-sbdt)}2]·2H 2O (4) and Cs2[CH2{VVO 2(sal-smdt)}2]·2H2O (6) are catalyst precursors for the catalytic oxidation of styrene by peroxide to yield styrene oxide, benzaldehyde, 1-phenylethane-1,2-diol, benzoic acid and phenylacetaldehyde. Plausible intermediates involved in these catalytic processes were established by UV/Vis, EPR and 51V NMR spectroscopic studies. The VVO2 complexes along with ligands I and II were also screened against HM1:1MSS strains of Entamoeba histolytica; the IC50 values of compounds 3, 4 and 5 were significantly lower than that of metronidazole, thereby suggesting that they may be promising drugs for the treatment of amoebiasis. Copyright
- Maurya, Mannar R.,Haldar, Chanchal,Khan, Aftab Alam,Azam, Amir,Salahuddin, Attar,Kumar, Amit,Costa Pessoa, Joao
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experimental part
p. 2560 - 2577
(2012/08/14)
-
- Assessment of enzymatic methods in the δ18O value determination of the l -tyrosine p -hydroxy group for proof of illegal meat and bone meal feeding to cattle
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The δ18O value of the p-hydroxy group of l-tyrosine depends on the biosynthesis by plants or animals, respectively. In animal proteins it reflects the diet and is therefore an absolute indicator for illegal feeding with meat and bone meal. The aim of this investigation was to perform the positional 18O determination on l-tyrosine via a one-step enzymatic degradation. Proteins from plants, herbivores, omnivores, and carnivores were characterized by their δ13C, δ15N, and δ18O values, the latter for normalizing the positional δ18O values. Their l-tyrosine was degraded by tyrosine phenol lyase to phenol, analyzed as (2,4,6)-tribromophenol. Degradation by tyrosine decarboxylase yielded tyramine. The δ18O values of both analytes corresponded to the trophic levels of their sources but were not identical, probably due to an isotope effect on the tyrosine phenol lyase reaction. Availability of the enzyme, easy control of the reaction, and isolation of the analyte are in favor of tyrosine decarboxylase degradation as a routine method.
- Tanz, Nicole,Werner, Roland A.,Eisenreich, Wolfgang,Schmidt, Hanns-Ludwig
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experimental part
p. 9475 - 9483
(2011/12/21)
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- Aqueous hydrogen peroxide and 2,4,4,6-tetrabromo-2,5-cyclohexadienone catalyst: An efficient mild ecofriendly cleaving reagent of thioacetals and thioketals
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A clean mild efficient dethioacetalization protocol is revealed utilizing a catalytic combination of 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TBCHD) (20 mol%) with 30% hydrogen peroxide as a terminal oxidizer in aqueous acetonitrile at room temperature. High yields of carbonyl compounds without overoxidation for oxidation-prone aromatic and furyl aldehydes, simple work-up, use of cost-compatible readily accessible reagents, tolerance of a wide range of common functional and protecting groups including phenolic hydroxy, methylenedioxy, acetoxy, aromatic amino, carbon-carbon double bond, allyl, benzyl, TBDPS ethers, NHBoc, NHBz are the key attractive features of the method.
- Ganguly, Nemai C.,Nayek, Subhasis,Barik, Sujoy Kumar
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experimental part
p. 251 - 256
(2012/03/11)
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- Facile, efficient, and catalyst-free electrophilic aminoalkoxylation of olefins: Scope and application
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A new one-pot electrophilic aminoalkoxylation reaction using olefin, cyclic ether, amine, and N-bromosuccinimide has been developed. The olefinic substrates and the cyclic ether partners can be flexibly varied to produce a range of amino ether derivatives. This novel protocol has been applied in the facile and efficient synthesis of biologically active morpholine compounds.
- Zhou, Ling,Tan, Chong Kiat,Zhou, Jing,Yeung, Ying-Yeung
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supporting information; scheme or table
p. 10245 - 10247
(2010/09/07)
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- Regioselective bromination of organic substrates by LDH-CO3 2--Br- promoted by V2O5-H 2O2
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An efficient, fast, simple, mild, and selective monobromination of aromatic compounds, with high para-selectivity, is reported. The catalytic system is readily prepared from a Mg-Al-layered double hydroxide-CO3 2--Br- (LDH-CO32--Br-) as the source of bromide, V2O5 as a promoter and hydrogen peroxide as the oxidant. The use of hydrogen peroxide as a synthetically useful oxidizing agent is reported for generating electrophilic bromine in situ from easily available KBr as a bromine source, to brominate electron rich aromatic compounds, employing LDH-CO32--Br3- as the phase-transfer catalyst. The phase-transfer catalyst leads to nearly complete bromination in 3 h at room temperature with high selectivity. The reaction rate of p-bromoanisole and p-bromotoluene formation by LDH-CO 32--Br3- in a triphasic system was studied. The heterogeneity of the reaction system facilitates the recovery and recycling of the catalyst, and the reagent components are environmentally acceptable. The catalyst, LDH-CO32--Br3 -, and its precursors, LDH-CO32--Br- and LDH-CO32-, were characterized by powder XRD, FT-IR and UV-vis spectroscopy.
- Ghiaci,Sedaghat,Ranjbari,Gil
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experimental part
p. 18 - 26
(2011/01/05)
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- PROCESS FOR THE PREPARATION OF 4-BROMOPHENYL DERIVATIVES
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Disclosed is a process for the preparation of a mixture of 4-bromophenyl derivatives (compound of formula (2)) and 2,4-dibromophenyl derivatives (compound of formula (3)) comprising the steps of [1] reacting in a two-phase (liquid-liquid) system a bromide containing source with a phenyl derivative (formula (1)) in the presence of an excess of an oxidizing agent, an acid, and optionally a catalyst selected from vanadium pentoxide and ammonium heptamolybdate forming 4-bromo- (compound of formula (2)) and 2,4-dibromo derivatives (compound of formula (3)) and as intermediate product the 2-bromo derivative (compound of formula (4)) which reacts in step [2] to the 2,4-dibromo derivative (formula (3)) according to the following reaction scheme 2 wherein R1 is hydroxy; C1-C5alkoxy; or -NR2R3; and R2 and R3 independently from each other are hydrogen; or C1-C5alkyl.
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Page/Page column 10
(2010/04/03)
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- Facile p-toluenesulfonic acid-promoted para-selective monobromination and chlorination of phenol and analogues
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para-Regioselective bromination of phenol and analogues, promoted by p-toluenesulfonic acid, is achieved in high to excellent yields at room temperature with N-bromosuccinimide. Chlorination with N-chlorosuccinimide and catalysed by p-toluenesulfonic acid also gives para-chlorinated phenol analogues in good yields at room temperature. para-Bromination of phenol, promoted by p-toluenesulfonic acid, is achieved in excellent yields at room temperature with N-bromosuccinimide. p-Toluenesulfonic acid is also effective as a promoter of para-chlorination with N-chlorosuccinimide.
- Bovonsombat, Pakorn,Ali, Rameez,Khan, Chiraphorn,Leykajarakul, Juthamard,Pla-On, Kawin,Aphimanchindakul, Suraj,Pungcharoenpong, Natchapon,Timsuea, Nisit,Arunrat, Anchalee,Punpongjareorn, Napat
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experimental part
p. 6928 - 6935
(2010/10/01)
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- Solvent-free phase-vanishing reactions with PTFE (Teflon) as a phase screen
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In a solvent-free phase-vanishing reaction with PTFE (polytetrafluoroethylene, Teflon) tape as the phase screen, a thermometer adapter is utilized to insert a PTFE-sealed tube into the vapor phase above the substrate. Besides avoiding use of solvents, the experimental design is not dependent upon the densities of the reactants and the procedure generates little or no waste while providing the reaction products in high yield and in high purity.
- Pels, Kevin,Dragojlovic, Veljko
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scheme or table
(2010/04/22)
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- Phase-vanishing reactions with ptfe (teflon) as a phase screen
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Phase-vanishing reactions are triphasic reactions, which involve a reagent, a liquid perfluoroalkane, and a substrate. In a phase-vanishing reaction with PTFE tape as the phase screen instead of a liquid perfluoroalkane, there is no limitation related to the density of a phase and the denser phase can be in the top layer. The reactions were faster compared to traditional PV reactions, and it was possible to carry out sequential and tandem reactions and reactions under a reflux.
- Van Zee, Nathan J.,Dragojlovic, Veljko
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supporting information; experimental part
p. 3190 - 3193
(2009/11/30)
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- Regioselective synthesis of phenols and halophenols from arylboronie acids using solid poly(N-vinylpyrrolidone)/hydrogen peroxide and poly(4-vinylpyridine) /hydrogen peroxide complexes
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Solid hydrogen peroxide complexes based on poly(N-vinylpyrrolidone) and poly(4-vinylpyridine) were prepared and used as solid hydroxylating reagents. These solid hydrogen peroxide equivalents are found to be much safer, convenient and efficient reagent systems for the ipso-hydroxylation of arylboronie acids to the corresponding phenols in high yields at a faster rate. The versatility of the reagents has been further expanded for the one-pot synthesis of halophenols. Density functional theory calculations were carried out on hydrogen peroxide complexes of N-ethylpyrrolidone and 4-ethylpyridine as models to get a better understanding of structure and behavior of hydrogen peroxide complexes of the polymers poly(N-vinylpyrrolidone) and poly(4-vinylpyridine) compared to aqueous hydrogen peroxide.
- Prakash, G. K. Surya,Chacko, Sujith,Panja, Chiradeep,Thomas, Tisa Elizabeth,Gurung, Laxman,Rasul, Golam,Mathew, Thomas,Olah, George A.
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experimental part
p. 1567 - 1574
(2011/02/25)
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- Dinuclear oxidovanadium(IV) and dioxidovanadium(V) complexes of 5,5′-methylenebis(dibasic tridentate) ligands: Synthesis, spectral characterisation, reactivity, and catalytic and antiamoebic activities
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The synthesis of dinuclear oxidovanadium(IV) and dioxidovanadium(V) complexes of two hydrazones [CH2(H2Salnah)2 (I) and CH2(H2sal-inh)2 (II)] derived from 5,5′-methylenebis(salicylaldehyde)
- Maurya, Mannar R.,Khan, Aftab Alam,Azam, Amir,Kumar, Amit,Ranjan, Samir,Mondal, Neelima,Costa Pessoa
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experimental part
p. 5377 - 5390
(2010/06/14)
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- Aromatization via a dibromination-double dehydrobromination sequence: A facile and convenient synthetic route to 2,6-bis(trifluoroacetyl)phenols
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An efficient and reliable method to synthesize 2,6-bis(trifluoroacetyl) phenols bearing various substituents in the 4-po-sition was developed. These valuable fluorinated building blocks were obtained from the corresponding cyclohexanones in a facile and convenient procedure, demonstrated to be superior to the traditional approaches. The application of this methodology to cyclohex-ane-1,4-dione opened access to 2,5-bis(polyfluoroacyl)-1,4- hydroquinones. Structural peculiarities of the obtained phenols as well as their 1,3-dicarbonyl or 1,3,5-tricarbonyl precursors are discussed on the basis of multinuclear NMR spectroscopy.
- Sevenard, Dmitri V.,Kazakova, Olesya,Schoth, Ralf-Matthias,Lork, Enno,Chizhov, Dmitri L.,Poveleit, Joern,Roeschenthaler, Gerd-Volker
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experimental part
p. 1867 - 1878
(2009/04/07)
-
- PRODUCTION OF TRIS (2,4,6-TRIBROMOPHENOXY-1,3,5-TRIAZINE)
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Tris(2,4,6-tribromophenoxy)-1,3,5-triazine , an effective flame retardant, is prepared by an efficient, low cost process. The process comprises (A) forming a mixture from 2,4,6- tribromophenol, alkali metal carbonate, and acetone as the solvent, refluxing the mixture to form a first reaction product mixture, (B) feeding cyanuric chloride portionwise to first reaction product mixture and refluxing the resultant mixture to form a solids-containing second reaction product mixture; C) recovering solids from second reaction product mixture, washing the solids with acetone and then with hot water, and thereafter drying the washed product.
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Page/Page column 4
(2008/12/06)
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- High-yielding cleavage of (aryloxy)acetates
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A reliable and high-yielding one-pot sequence for the removal of O-carboxymethyl moieties from phenols is presented. When diethylphosphoryl azide is employed as the azide transfer reagent in the Curtius rearrangement and glycerol in the subsequent hydrolytic workup, the protocol can be reliably applied to a very broad scope of substrates. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Spurg, Anke,Waldvogel, Siegfried R.
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p. 337 - 342
(2008/09/18)
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- Regioselective bromination of activated aromatic substrates with a ZrBr4/diazene mixture
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A regioselective method for the bromination of phenols, ethers and anilines using a ZrBr4/diazene mixture is described. The reaction takes place under mild reaction conditions and the bromine atom adds first at the para unsubstituted position with respect to the OH, OR or NR2 group of the activated aromatic substrate. Less reactive compounds such as toluene, phenyl acetate, benzonitrile and trifluoromethylbenzene remain intact under the same conditions.
- Stropnik, Tadej,Bombek, Sergeja,Ko?evar, Marijan,Polanc, Slovenko
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p. 1729 - 1733
(2008/09/18)
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- Regioselective aromatic electrophilic bromination with dioxane dibromide under solvent-free conditions
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Highly regioselective ring bromination of aromatic compounds has been accomplished with high yields and good purity using dioxane dibromide (DD) under solvent-free conditions. Notable features of this methodology include operational simplicity, rapid reactions, excellent control over the degree of bromination, and tolerance of various functional groups during the reaction. Copyright Taylor & Francis Group, LLC.
- Chaudhuri, Subrata Kumar,Roy, Sanchita,Saha,Bhar, Sanjay
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p. 581 - 585
(2007/10/03)
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- Fluorescence enhancements of benzene-cored luminophors by restricted intramolecular rotations: AIE and AIEE effects
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Photoluminescence of simple arylbenzenes with ready synthetic accessibility is enhanced by two orders of magnitude through aggregate formation; viscosity and temperature effects indicate that the emission enhancement is due to the restriction of their intramolecular rotations in the solid state. The Royal Society of Chemistry.
- Zeng, Qi,Li, Zhen,Dong, Yongqiang,Di, Chong'an,Qin, Anjun,Hong, Yuning,Ji, Li,Zhu, Zhichao,Jim, Cathy K. W.,Yu, Gui,Li, Qianqian,Li, Zhongan,Liu, Yunqi,Qin, Jingui,Tang, Ben Zhong
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