- Selective Bromination of β-Positions of Porphyrin by Self-Catalytic Behaviour of VOTPP: Facile Synthesis, Electrochemical Redox Properties and Catalytic Application
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Oxidovanadium(IV) complex of β-octabromo-meso-tetraphenylporphyrin, {[VIVO(TPPBr8)], 2} was synthesized by self-catalytic oxidative bromination of meso-tetraphenylporphyrinatooxidovanadium(IV) {[VIVO(TPP), 1} in excellent yield under mild conditions at 25 °C and its structure was confirmed by single crystal X-ray study. UV-Vis and 1H NMR spectra further confirmed that the meso-phenyl rings are not brominated and thus emphasizes on the selectivity as well as synthetic importance of this catalytic method. In the presence of substrates e. g. phenol derivatives, 1 biomimics the vanadium bromoperoxidase (VBPO) enzyme and catalyses the oxidative bromination of substrates in water at 25 °C. Remarkably, 2 also catalyses the oxidative bromination of phenol derivatives under similar reaction conditions with very high turnover frequency (TOF) values (ca. 29 s?1) along with its recyclability. It was found that 2 showed superior catalytic performance as compared to 1 because of its electron deficient nature due to electron withdrawing bromo substituents and robust saddle shaped nonplanar structure (further supported by DFT studies).
- Maurya, Mannar R.,Prakash, Ved,Avecilla, Fernando,Sankar, Muniappan
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p. 1685 - 1694
(2021/05/03)
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- Microflow fluorinations of benzynes: Efficient synthesis of fluoroaromatic compounds
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Fluorinated aromatic compounds are found in a variety of biologically active compounds, including clinical drugs and agrochemicals. Therefore, the synthesis of aryl fluorides is particularly important in the medicinal and process chemistry fields. In this
- Ikawa, Takashi,Masuda, Shigeaki,Akai, Shuji
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p. 1153 - 1164
(2018/12/10)
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- Green halogenation reactions for (hetero)aromatic ring systems in alcohol, water, or no solvent
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A new method of brominating aromatic and heteroaromatic ring systems is investigated. The combination of hydrobromic acid as the halogen source, hydrogen peroxide as the oxidant, and ethanol, water, or no solvent are evaluated as greener conditions than those that have been previously published. The new conditions give high yields and good regioselectivity for a variety of substrates when the ring is activated by electron-donating groups or heteroatoms. Phenols, anisole, thiophenes, and pyrrole give comparable or superior results when compared to a traditional bromination by N-bromosuccinimide in tetrahydrofuran. Other nitrogen-containing heterocycles do not react under the conditions because they are protonated and hence deactivated; similarly, substrates with electron-withdrawing groups are not brominated. The reaction is very tolerant of a variety of functional groups.
- Kajorinne, Jessie K.,Steers, Jennifer C.M.,Merchant, Marnie E.,MacKinnon, Craig D.
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p. 1087 - 1091
(2018/11/25)
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- Selective and efficient generation of ortho-brominated para-substituted phenols in ACS-grade methanol
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The mono ortho-bromination of phenolic building blocks by NBS has been achieved in short reaction times (15-20 min) using ACS-grade methanol as a solvent. The reactions can be conducted on phenol, naphthol and biphenol substrates, giving yields of >86% on gram scale. Excellent selectivity for the desired mono ortho-brominated products is achieved in the presence of 10 mol % para-TsOH, and the reaction is shown to be tolerant of a range of substituents, including CH3/ F,and NHBoc.
- Georgiev, David,Saes, Bartholomews W.H.,Johnston, Heather J.,Boys, Sarah K.,Healy, Alan,Hulme, Alison N.
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- Binuclear complexes of Ni(i) from 4-terphenyldithiophenol
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Binuclear complexes of Ni(i) have been prepared from a 4-terphenyldithiophenol ligand. Steric effects were found to determine the formation of coordination isomeric structures that differ in the nature of metal-to-ligand bonding. Coordination of spatially
- Koch, Felix,Schubert, Hartmut,Sirsch, Peter,Berkefeld, Andreas
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supporting information
p. 13315 - 13324
(2016/01/09)
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- Environmentally benign electrophilic and radical bromination 'on water': H2O2-HBr system versus N-bromosuccinimide
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A H2O2-HBr system and N-bromosuccinimide in an aqueous medium were used as a 'green' approach to electrophilic and radical bromination. Several activated and less activated aromatic molecules, phenylsubstituted ketones and styrene were efficiently brominated 'on water' using both systems at ambient temperature and without an added metal or acid catalyst, whereas various non-activated toluenes were functionalized at the benzyl position in the presence of visible light as a radical activator. A comparison of reactivity and selectivity of both brominating systems reveals the H2O2-HBr system to be more reactive than NBS for benzyl bromination and for the bromination of ketones, while for electrophilic aromatic substitution of methoxy-substituted tetralone it was higher for NBS. Also, higher yields of brominated aromatics were observed when using H2O2-HBr 'on water'. Bromination of styrene reveals that not just the structure of the brominating reagent but the reaction conditions: amount of water, organic solvent, stirring rate and interface structure, play a key role in defining the outcome of bromination (dibromination vs bromohydroxylation). In addition, mild reaction conditions, a straightforward isolation procedure, inexpensive reagents and a lower environment impact make aqueous brominating methods a possible alternative to other reported brominating protocols.
- Podgor?ek, Ajda,Stavber, Stojan,Zupan, Marko,Iskra, Jernej
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experimental part
p. 4429 - 4439
(2009/10/09)
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- Design, synthesis, and biological evaluation of novel diarylalkyl amides as TRPV1 antagonists
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We have developed a new class of diarylalkyl amides as novel TRPV1 antagonists. They exhibited potent 45Ca2+ uptake inhibitions in rat DRG neuron. In particular, the amide 59 was identified as a potent antagonist with IC50 of 57 nM. The synthesis and structure-activity relationship of the diarylalkyl amides are also described.
- Li, Fu-Nan,Kim, Nam-Jung,Paek, Seung-Mann,Kwon, Do-Yeon,Min, Kyung Hoon,Jeong, Yeon-Su,Kim, Sun-Young,Park, Young-Ho,Kim, Hee-Doo,Park, Hyeung-Geun,Suh, Young-Ger
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experimental part
p. 3557 - 3567
(2009/09/27)
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- Binucleating ligands: Synthesis of acyclic achiral and chiral Schiff base-pyridine and Schiff base-phosphine ligands
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5-tert-Butyl-3-(2′-pyridyl)salicyaldehyde and 5-tert-butyl-3-(diphenylphosphino)salicyaldehyde were synthesized from 4-tert-butylphenol in good overall yields. Condensation of the salicyaldehydes with 2,3-diamino-2,3-dimethylbutane afforded the desired dinucleating Schiff base-pyridine and Schiff base-phosphine ligands, respectively. 5-tert-Butyl-3-(2′-pyridyl)salicyaldehyde reacted with optically active 1,2-diaminocyclohexanes to give chiral dinucleating Schiff base-pyridine ligands.
- Lam, Fung,Xu, Jia Xi,Chan, Kin Shing
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p. 8414 - 8418
(2007/10/03)
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- Synthesis of acyclic dinucleating Schiff base-pyridine and Schiff base-phosphine ligands
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5-tert-butyl-3-pyridyl-salicyaldehyde and 5-tert-butyl-3-diphenylphosphino-salicyaldehyde have been synthesized from 4-tert-butylphenol in good overall yields. Condensation of the salicyaldehydes with 2,3-diamino-2,3-dimethylbutane afforded the desired dinucleating Schiff base-pyridine and Schiff base-phosphine ligands respectively.
- Lam, Fung,Chan, Kin Shing
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p. 919 - 922
(2007/10/02)
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- Nitrocyclohexadienones : a new class of nitrating agents
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Various nitrocyclohexadienones are proposed as new nitrating agents. These compounds are easy to prepare from corresponding phenols, easy to handle and stable. Nitrocyclohexadienones act as nitronium carriers using rearomatization as the driving force and permit nitration of highly activated substrates under mild conditions and with good yields.
- Lemaire, Marc,Guy, Alain,Roussel, Jacques,Guette, Jean-paul
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p. 835 - 844
(2007/10/02)
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- 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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p. 627 - 630
(2007/10/02)
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- Improved Acylation Rates within Cyclodextrin Complexes from Flexible Capping of the Cyclodextrin and from Adjustment of the Substrate Geometry
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The acylation of β-cyclodextrin by bound substrates has been studied as a model for serine acylase enzymes such as chymotrypsin.Molecular model building suggested that previously examined substrates, which had given acylation rates only a few hundred times accelerated over the hydrolysis rates, were not optimal geometrically.In our work the geometry for such processes has been improved by fashioning an "intrusive floor" on the cyclodextrin cavity, leading to improved rates.Greater improvements have come from substrate modification, using substrates based on the cinnamic acid, adamantane, and ferrocene frameworks.The rates correlate well with the geometric predictions from molecular models.The best case leads to an acceleration of acylation, relative to hydrolysis, of 106-107-fold, exceeding that for chymotrypsin with p-nitrophenyl acetate.
- Breslow, Ronald,Czarniecki, Michael F.,Emert, Jack,Hamaguchi, Hiroshi
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p. 762 - 770
(2007/10/02)
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- Process for preparing pyrogallol
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Pyrogallol is prepared by (A) reacting a halo compound of formula STR1 where X represents Br or I, R1 represents hydrogen, secondary or tertiary alkyl of up to 10 carbon atoms, carboxy or alkoxycarbonyl of 2-5 carbon atoms and R2 represents hydrogen or alkyl of 1-4 carbon atoms, with an alkali metal alkoxide of formula ROM where M represents an alkali metal and R represents alkyl of 1-4 carbon atoms, to replace each X by OR, and then (B) dealkylating each OR and each OR2 where R2 represents alkyl of 1-4 carbon atoms and removing the R1 group where this is not hydrogen.
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