- A Tethered Tolane: Twisting the Excited State
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The synthesis of a doubly bridged tolane is reported. The target is obtained in a five-step synthesis, starting from commercially available 2-amino-meta-xylene by a combination of a Sandmeyer reaction, radical bromination, and Stille-type coupling, followed by double ring closing. The doubly tethered tolane is crystalline; the two phenyl rings are highly twisted with respect to each other both in solution and in the solid state. Optical spectroscopy and quantum chemical calculations show that the doubly bridged tolane is twisted not only in the ground state, but also in the excited state, leading to emission from the twisted state in solution and in the solid state. Strong phosphorescence is observed at cryogenic temperatures.
- Kozhemyakin, Yury,Kr?mer, Maximilian,Rominger, Frank,Dreuw, Andreas,Bunz, Uwe H. F.
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supporting information
p. 15219 - 15222
(2018/09/21)
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- Synthesis and biological evaluation of thielocin B1 analogues as protein-protein interaction inhibitors of PAC3 homodimer
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The synthesis and biological evaluation of thielocin B1 analogues have been demonstrated. Fourteen analogues modified in the central core and terminal carboxylic acid moiety were concisely synthesized by simple esterification or etherification reaction. The evaluation of synthetic analogues as inhibitors of proteasome assembling chaperone (PAC) complexes (the PAC3 homodimer and PAC1/PAC2) revealed that the natural product-like bending structure and terminal carboxylic acid groups were crucial for its biological activity. Moreover, SAR and in silico docking studies indicated that all methyl groups on the diphenyl ether moiety of thielocin B1 contribute to the potent and selective inhibition of the PAC3 homodimer via hydrophobic interactions.
- Ohsawa, Kosuke,Yoshida, Masahito,Izumikawa, Miho,Takagi, Motoki,Shin-ya, Kazuo,Goshima, Naoki,Hirokawa, Takatsugu,Natsume, Tohru,Doi, Takayuki
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supporting information
p. 6023 - 6034
(2018/11/23)
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- Transition-metal-free decarboxylative bromination of aromatic carboxylic acids
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Methods for the conversion of aliphatic acids to alkyl halides have progressed significantly over the past century, however, the analogous decarboxylative bromination of aromatic acids has remained a longstanding challenge. The development of efficient methods for the synthesis of aryl bromides is of great importance as they are versatile reagents in synthesis and are present in many functional molecules. Herein we report a transition metal-free decarboxylative bromination of aromatic acids. The reaction is applicable to many electron-rich aromatic and heteroaromatic acids which have previously proved poor substrates for Hunsdiecker-type reactions. In addition, our preliminary mechanistic study suggests that radical intermediates are not involved in this reaction, which is in contrast to classical Hunsdiecker-type reactivity. Overall, the process demonstrates a useful method for producing valuable reagents from inexpensive and abundant starting materials.
- Quibell, Jacob M.,Perry, Gregory J. P.,Cannas, Diego M.,Larrosa, Igor
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p. 3860 - 3865
(2018/04/26)
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- Process for Preparing Chloro-and Bromoaromatics
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The present invention relates to a novel process for preparing chloro- or bromoaromatics of the formula (II) by diazotizing the formula (I) by means of sodium nitrite or potassium nitrite in the presence of aqueous hydrochloric or hydrobromic acids and then reacting with an iron(II) or iron(III) compound, optionally in the presence of additional amounts of hydrogen chloride or hydrogen bromide or alkali metal or alkaline earth metal chlorides or bromides.
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Page/Page column 5
(2010/09/18)
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- Efficient one-pot transformation of aminoarenes to haloarenes using halodimethylisulfonium halides generated in situ
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Halodimethylsulfonium halide 1, which is readily formed in situ from hydrohaloic acid and DMSO, is a good nucleophilic halide. This activated nucleophilic halide rapidly converts aryldiazonium salt prepared in situ by the same hydrohaloic acid and nitrite ion to aryl chlorides, bromides, or iodides in good yield. The combined action of nitrite ion and hydrohaloic acid in DMSO is required for the direct transformation of aromatic amines, which results in the production of aryl halides within 1 h. Substituted compounds with electron-donating or -withdrawing groups or sterically hindered aromatic amines are also smoothly transformed to the corresponding aromatic halides. The only observed by-product is the deaminated arene (usually 7%). The isolated aryldiazonium salts can also be converted to the corresponding aryl halides using 1. The present method offers a facile, one-step procedure for transforming aminoarenes to haloarenes and lacks the environmental pollutants that usually accompany the Sandmeyer reaction using copper halides.
- Baik, Woonphil,Luan, Wanqiang,Lee, Hyun Joo,Yoon, Cheol Hun,Koo, Sangho,Kim, Byeong Hyo
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p. 213 - 219
(2007/10/03)
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- Efficient method for the preparation of aromatic bromides and iodides by ferrocenium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate-catalyzed halogenation with bromine and iodine monochloride
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Direct iodination and bromination of various aromatic compounds with 1.1-2.0 molar amounts of iodine monochloride (ICl) and 1.1-3.0 molar amounts of bromine proceeded smoothly to afford the corresponding aromatic iodides and bromides, respectively, in good to excellent yields by using 0.05 molar amount of ferrocenium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, Cp2FeB[3,5-(CF3)2C6H 3]4 (1), in the presence of ZnO. Iodination of toluene in the co-existence of 0.5 molar amount of DDQ also proceeded to give iodotoluenes in high yield.
- Kitagawa, Hideo,Shibata, Tsuyoshi,Matsuo, Jun-Ichi,Mukaiyama, Teruaki
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p. 339 - 345
(2007/10/03)
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- Aromatic Spiranes XX [1]: Syntheses of Dimethylsubstituted 2-Carboxymethyl-indan-1-ones and Benzylchlorides as Synthones for Syntheses of di- to tetramethylsubstituted Spirobiindandiones
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The isomeric dimethyl methylbenzoates 5, obtained from the bromides via Grignard reactions with dimethylcarbonate, were reduced with LiAlH4 to the hydroxymethyl derivatives 6. The latter were then transformed both to the benzylchlorides 7 (with SOCl2) and to the aldehydes 8 (with pyridinium chlorochromate). Knoevenagel-Doebner reaction of 8 afforded the acrylic acids 9 which (after hydrogenation to 11) were cyclized to the desired indanones 12 with polyphosphoric acid. On the other hand, 12c and 12e were prepared from dimethyl 3-chloropropiophenone (14) by warming with sulfuric acid. After NaH-catalyzed reaction with dimethylcarbonate, the indanones 12 gave the ketoesters 15 which then could be hydrogenated to the indanes 16. All reactions proceeded with satisfactory to excellent yields (60-90%).
- Neudeck
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p. 185 - 200
(2007/10/03)
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- Protonation-induced Isomerization of Gaseous Bromoxylenes : a Radiolytic and Mass Spectrometric Study
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The isomerization of bromoxylenes following protonation by X3+ (X=H or D), CnH5+ (n=1 or 2), iso-C3H7+, and t-C4H9+ ions in the dilute gas state has been investigated.Further evidence has been derived from chemical ionization mass spectrometry and related radiolytic experiments concerning methylation of bromotoluenes by gaseous (CH3)2F+ ions.The results suggest that the observed intramolecular Br migration involves the intermediacy of a radical cation-bromine atom pair.The mechanistic relevance of the results to gas-phase aromatic substitution by free bromine cations is discussed.
- Cacace, Fulvio,Ciranni, Giovanna,Marzio, Annito Di
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p. 775 - 780
(2007/10/02)
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- Process for the preparation of 2,6-dialkylaniline from brominated dialkyl t-butylbenzene
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A process for the preparation of 2,6-dialkylaniline which comprises the reaction of 1,3-dialkyl-5-tertiary-butylbenzene with molecular bromine to form 2-bromo-1,3-dialkyl-5-tertiary-butylbenzene, which is subsequently reacted with 1,3-dialkylbenzene in the presence of hydrogen fluoride to form a mixture of 2-bromo-1,3-dialkylbenzene and 1,3-dialkyl-5-tertiary-butylbenzene, which is then reacted with ammonia in the presence of a catalytic amount of cuprous halide.
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- Regioselective Ring Opening in Substituted Benzocyclopropenes. An Alternative or Complementary Mechanism for Electrophilic Substitution Involving Attack at a ? Bond
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2-Methylbenzocyclopropene (5) reacts with bromine, iodine, and HCl to give the m-xylenes 12a,c,d as the major products, whereas it reacts with silver nitrate in the presence of ethanol and aniline to give the o-xylenes 11e,f as the major products.Similarly, 3-methylbenzocyclopropene (10) gives mainly m-xylenes 14a,c,d with halogens and HCl and gives p-xylenes 13e,f with silver nitrate and ethanol or aniline.Cyclopropabenzocyclobutene (15) also gives different products with halogens and silver nitrate, but in this case HCl gives the same type of product as the silver ion.The difference in electrophilic behavior of 5, 10, and 15 toward the two types of reagents is suggested to arise from attack of the silver ion (and the proton in the case of 15) on the ? electrons of the cyclopropyl ring.
- Bee, Lim Keow,Garratt, Peter J.,Mansuri, Muzamil M.
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p. 7076 - 7079
(2007/10/02)
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