- Crown-containing spironaphthoxazines and spiropyrans 3. Synthesis and investigation of the merocyanine form of crown-containing spirobenzothiazolinonaphthoxazine
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A method for the synthesis of the spirobenzothiazolinonaphthoxazine, stable in the merocyanine form and containing a crown-ether fragment was developed. The complexing properties of the prepared merocyanine compound and the spectroscopic and photochromic characteristics of its complexes with alkaline earth metal cations were studied by NMR and UV spectroscopy. The results were analyzed using quantum-chemical calculations. The addition of alkaline earth metal perchlorates to a solution of a crown ether-containing merocyanine dye in MeCN results in the coordination of metal cations to two binding centers, namely, the crown-ether fragment and the merocyanine oxygen atom. This gives rise to two types of complexes, which differ substantially in their structurally. The complexation induces changes in the UV spectra and influences on the photochromic behavior of the prepared compound.
- Fedorova,Koshkin,Gromov,Avakyan,Nazarov,Brichkin,Vershinnikova,Nikolaeva,Chernych,Alfimov
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- Anti-inflammatory, ulcerogenic and platelet activation evaluation of novel 1,4-diaryl-1,2,3-triazole neolignan-celecoxib hybrids
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This study reports the synthesis of novel neolignans-celecoxib hybrids and the evaluation of their biological activity. Analogs 8–13 (L13-L18) exhibited anti-inflammatory activity, inhibited glycoprotein expression (P-selectin) related to platelet activation, and were considered non– ulcerogenic in the animal model, even with the administration of 10 times higher than the dose used in reference therapy. In silico drug-likeness showed that the analogs are compliant with Lipinski's rule of five. A molecular docking study showed that the hybrids 8–13 (L13-L18) fitted similarly with celecoxib in the COX-2 active site. According to this data, it is possible to infer that extra hydrophobic interactions and the hydrogen interactions with the triazole core may improve the selectivity towards the COX-2 active site. Furthermore, the molecular docking study with P-selectin showed the binding affinity of the analogs in the active site, performing important interactions with amino acid residues such as Tyr 48. Whereas the P-selectin is a promising target to the design of new anti-inflammatory drugs with antithrombotic properties, a distinct butterfly-like structure of 1,4-diaryl-1,2,3-triazole neolignan-celecoxib hybrids synthesized in this work may be a safer alternative to the traditional COX-2 inhibitors.
- Baroni, Adriano C. M.,Carvalho, Diego B.,Carvalho, Maria G.,Cassamale, Tatiana B.,Duarte, Rita C. F.,Felipe, Josyelen L.,Louren?o, Leticia D.,Toffoli-Kadri, Monica C.,das Neves, Amarith R.
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- Direct bromodeboronation of arylboronic acids with CuBr2 in water
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An efficient and practical method has been developed for the preparation of aryl bromides via the direct bromodeboronation of arylboronic acids with CuBr2 in water. This strategy provides several advantages, such as being ligand-free, base-free, high yielding, and functional group tolerant.
- Tang, Yan-Ling,Xia, Xian-Song,Gao, Jin-Chun,Li, Min-Xin,Mao, Ze-Wei
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supporting information
(2021/01/05)
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- Bis-selenonium Cations as Bidentate Chalcogen Bond Donors in Catalysis
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Lewis acids are frequently employed in catalysis but they often suffer from high moisture sensitivity. In many reactions, catalysts are deactivated because of the problem that strong Lewis acids also bond to the products. In this research, hydrolytically stable bidentate Lewis acid catalysts derived from selenonium dicationic centers have been developed. The bis-selenonium catalysts are employed in the activation of imine and carbonyl groups in various transformations with good yields and selectivity. Lewis acidity of the bis-selenonium salts was found to be stronger than that of the monoselenonium systems, attributed to the synergistic effect of the two cationic selenonium centers. In addition, the bis-selenonium catalysts are not inhibited by strong bases or moisture.
- He, Xinxin,Wang, Xinyan,Tse, Ying-Lung Steve,Ke, Zhihai,Yeung, Ying-Yeung
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p. 12632 - 12642
(2021/10/21)
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- Visible light-induced mono-bromination of arenes with BrCCl3
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A highly efficient and regioselective bromination of electron-rich arenes and heteroarenes using commercially available BrCCl3as a “Br” source has been developed. The reaction was performed in air under mild conditions with photocatalyst Ru(bpy)3Cl2·6H2O, avoiding the usage of strong acids and strong oxidants. Mono-brominated products were obtained with medium to excellent yields (up to 94%). This strategy has shown good compatibility and highpara-selectivity, which will facilitate the complicated synthesis.
- Fan, Jiali,Wei, Qiancheng,Zhu, Ershu,Gao, Jing,Cheng, Xiamin,Lu, Yongna,Loh, Teck-Peng
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supporting information
p. 5977 - 5980
(2021/06/18)
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- Eco-Friendly Methodology for the Formation of Aromatic Carbon–Heteroatom Bonds by Using Green Ionic Liquids
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A new sustainable method is reported for the formation of aromatic carbon–heteroatom bonds under solvent-free and mild conditions (no co-oxidant, no strong acid and no toxic reagents) by using a new type of green ionic liquid. The bromination of methoxy arenes was chosen as a model reaction. The reaction methodology is based on only using natural sodium bromine, which is transformed into an electrophilic brominating reagent within an ionic liquid, easily prepared from the melted salt FeCl3 hexahydrate. Bromination reactions with this in-situ-generated reagent gave good yields and excellent regioselectivity under simple and environmentally friendly conditions. To understand the unusual bromine polarity reversal of sodium bromine without any strong oxidant, the molecular structure of the reaction medium was characterised by Raman and direct infusion electrospray ionisation mass spectroscopy (ESI-MS). An extensive computational investigation using density functional theory methods was performed to describe a mechanism that suggests indirect oxidation of Br? through new iron adducts. The versatility of the methodology was successively applied to nitration and thiocyanation of methoxy arenes using KNO3 and KSCN in melted hexahydrated FeCl3.
- Richards, Kenza,Petit, Eddy,Legrand, Yves-Marie,Grison, Claude
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supporting information
p. 809 - 814
(2020/11/30)
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- Cooperativity within the catalyst: alkoxyamide as a catalyst for bromocyclization and bromination of (hetero)aromatics
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Alkoxyamide has been reported as a catalyst for the activation ofN-bromosuccinimide to perform bromocyclization and bromination of a wide range of substrates in a lipophilic solvent, where adequate suppression of the background reactions was observed. The key feature of the active site is the alkoxy group attached to the sulfonamide moiety, which facilitates the acceptance as well as the delivery of bromonium species from the bromine source to the substrates.
- Mondal, Haripriyo,Sk, Md Raja,Maji, Modhu Sudan
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supporting information
p. 11501 - 11504
(2020/10/12)
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- Design, synthesis and antitrypanosomatid activities of 3,5-diaryl-isoxazole analogues based on neolignans veraguensin, grandisin and machilin G
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Using bioisosterism as a medicinal chemistry tool, 16 3,5-diaryl-isoxazole analogues of the tetrahydrofuran neolignans veraguensin, grandisin and machilin G were synthesized via 1,3-dipolar cycloaddition reactions, with yields from 43% to 90%. Antitrypanosomatid activities were evaluated against Trypanosoma cruzi, Leishmania (L.) amazonensis and Leishmania (V.) braziliensis. All compounds were selective for the Leishmania genus and inactive against T.?cruzi. Isoxazole analogues showed a standard activity on both promastigotes of L.?amazonensis and L.?braziliensis. The most active compounds were 15, 16 and 19 with IC50 values of 2.0, 3.3 and 9.5?μM against L.?amazonensis and IC50 values of 1.2, 2.1 and 6.4?μM on L.?braziliensis, respectively. All compounds were noncytotoxic, showing lower cytotoxicity (>250?μM) than pentamidine (78.9?μM). Regarding the structure–activity relationship (SAR), the methylenedioxy group was essential to antileishmanial activity against promastigotes. Replacement of the tetrahydrofuran nucleus by an isoxazole core improved the antileishmanial activity.
- Trefzger, Ozildéia S.,das Neves, Amarith R.,Barbosa, Natália V.,Carvalho, Diego B.,Pereira, Indiara C.,Perdomo, Renata T.,Matos, Maria F. C.,Yoshida, Nidia C.,Kato, Massuo J.,de Albuquerque, Sérgio,Arruda, Carla C. P.,Baroni, Adriano C. M.
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p. 313 - 324
(2018/11/30)
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- Regioselective Oxybromination of Benzene and Its Derivatives by Bromide Anion with a Mononuclear Nonheme Mn(IV)-Oxo Complex
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Oxybromination of aromatic compounds by high-valent metal-oxo intermediates has yet to be explored despite extensive studies on the oxybromination of aliphatic C-H bonds of hydrocarbons. Herein, we report the regioselective oxybromination of methoxy-substituted benzenes by a nonheme MnIV-oxo complex binding scandium ions, [(Bn-TPEN)MnIV(O)]2+-(Sc(OTf)3)2 (1), in the presence of tetrabutylammonium bromide. The regioselective oxybromination occurs at the carbon atom with the highest positive charge via electron transfer (ET) from the methoxy-substituted benzenes to 1. ET driving force dependence of the rate constants of ET from methoxy-substituted benzenes to 1 is well fitted in light of the Marcus theory of ET. Under photoirradiation, the oxybromination of benzene by 1 can be achieved via ET from benzene to the photoexcited state of 1, although no reaction occurs between benzene and the ground state of 1 in the dark. To the best of our knowledge, this is the first example of reporting the stoichiometric regioselective oxybromination of the benzene ring by a synthetic high-valent Mn(IV)-oxo complex and the catalytic regioselective oxybromination reaction with a Mn(II) complex and a terminal oxidant.
- Sharma, Namita,Lee, Yong-Min,Li, Xiao-Xi,Nam, Wonwoo,Fukuzumi, Shunichi
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supporting information
p. 14299 - 14303
(2019/11/03)
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- Atom-economical brominations with tribromide complexes in the presence of oxidants
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Bromination is an important transformation in organic synthesis, and novel efficient bromination techniques are still required. Herein, we demonstrate atom-economical brominations using (DMI)2HBr3, a novel tribromide complex, with oxidants such as DMSO and Oxone. Using this system, olefinic and aromatic brominations, as well as selective α-monobrominations of ketones proceeded well to afford the desired bromides in good yields. Importantly, in these reactions all of the bromine atoms in this complex are used to brominate.
- Yubata, Kotaro,Matsubara, Hiroshi
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supporting information
p. 1001 - 1004
(2019/03/13)
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- Regioselective bromination of arenes mediated by triphosgene-oxidized bromide
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This article first time describes triphosgene (BTC) as an oxidant while the non-toxic and easy-to-handle potassium bromide (KBr) as the source of bromine to the bromination reaction of aromatic substrates. The novel brominating protocol gives excellent para-regioselectivity of the alkoxyl/hydroxyl arenes and high yield, offering good potential of commercial scale applications. The mechanism of “Triphosgene oxidize bromide” was proposed.
- Xu, Yingzhou,Hu, Dufen,Zheng, Hui,Mei, David,Gao, Zhaobo
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supporting information
(2019/08/30)
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- Applications of Selenonium Cations as Lewis Acids in Organocatalytic Reactions
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The use of trisubstituted selenonium salts as organic Lewis acids in electrophilic halogenation and aldol-type reactions has been developed. The substrate scope is broad. The reaction conditions are mild and compatible with various functionalities. This study opens a new avenue for the development of nonmetallic Lewis acid catalysis.
- He, Xinxin,Wang, Xinyan,Tse, Ying-Lung (Steve),Ke, Zhihai,Yeung, Ying-Yeung
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supporting information
p. 12869 - 12873
(2018/09/14)
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- Environmentally benign indole-catalyzed position-selective halogenation of thioarenes and other aromatics
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Halogenated aromatic compounds are the cores of many pharmaceutical, agricultural and chemical products but they are commonly prepared using electrophilic halogenation reactions in non-green chlorinated solvents under harsh conditions. A separate problem happens in the aromatic halogenation of thioarenes because they readily undergo oxidative side-reactions. Herein we report an environmentally benign electrophilic bromination of aromatics using an indole-catalytic protocol, which is suitable for a wide range of substrates including thioarenes.
- Shi, Yao,Ke, Zhihai,Yeung, Ying-Yeung
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supporting information
p. 4448 - 4452
(2018/10/17)
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- Zwitterionic-Salt-Catalyzed Site-Selective Monobromination of Arenes
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A zwitterionic-salt-catalyzed electrophilic monobromination of arenes with high regioselectivity has been developed. Under mild reaction conditions, a wide range of monobrominated aromatic compounds can be obtained in excellent yields. The reaction can be operated using an extremely low catalyst loading (0.05 mol %) with the inexpensive brominating agent N-bromosuccinimide. The versatility of this catalytic protocol has been demonstrated by the scale-up reaction with a 0.01 mol % catalyst loading to provide the selectively halogenated compound in quantitative yield.
- Xiong, Xiaodong,Tan, Fei,Yeung, Ying-Yeung
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supporting information
p. 4243 - 4246
(2017/08/23)
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- Synthesis and Antitrypanosomastid Activity of 1,4-Diaryl-1,2,3-triazole Analogues of Neolignans Veraguensin, Grandisin and Machilin G
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Sixteen 1,4-diaryl-1,2,3-triazole compounds derived from the natural products veraguensin, grandisin and machilin G were synthesized, with yields of 78-92percent. Biological activity tests against Leishmania amazonensis promastigotes showed that three of these compounds were the most active, with maximum inhibitory concentration (IC50 ) values of 1.1, 3.71 and 7.23 μM. One compound was highly active against Leishmania infantum, with an IC50 value of 5.2 μM, and one derivative showed an IC50 value of 28.6 μM against Trypanosoma cruzi trypomastigotes. Regarding structureactivity relationship (SAR), hybrid 1,2,3-triazolic compounds containing a methylenedioxy group, showed the best antileishmanial and antitrypanosomal activities.
- Cassamale, Tatiana B.,Costa, Eduarda C.,Carvalho, Diego B.,Cassemiro, Nadla S.,Tomazela, Carolina C.,Marques, Maria C. S.,Ojeda, Mariáh,Matos, Maria F. C.,Albuquerque, Sérgio,Arruda, Carla C. P.,Baroni, Adriano C. M.
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p. 1217 - 1228
(2016/08/25)
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- Antileishmanial activity and structure-activity relationship of triazolic compounds derived from the neolignans grandisin, veraguensin, and machilin G
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Sixteen 1,4-diaryl-1,2,3-triazole compounds 4-19 derived from the tetrahydrofuran neolignans veraguensin 1, grandisin 2, and machilin G 3 were tested against Leishmania (Leishmania) amazonensis intracellular amastigotes. Triazole compounds 4-19 were synthetized via Click Chemistry strategy by 1,3-dipolar cycloaddition between terminal acetylenes and aryl azides containing methoxy and methylenedioxy groups as substituents. Our results suggest that most derivatives were active against intracellular amastigotes, with IC50 values ranging from 4.4 to 32.7 μM. The index of molecular hydrophobicity (ClogP) ranged from 2.8 to 3.4, reflecting a lipophilicity/hydrosolubility rate suitable for transport across membranes, which may have resulted in the potent antileishmanial activity observed. Regarding structure-activity relationship (SAR), compounds 14 and 19, containing a trimethoxy group, were the most active (IC50 values of 5.6 and 4.4 μM, respectively), with low cytotoxicity on mammalian cells (SI = 14.1 and 10.6). These compounds induced nitric oxide production by the host macrophage cells, which could be suggested as the mechanism involved in the intracellular killing of parasites. These results would be useful for the planning of new derivatives with higher antileishmanial activities.
- Costa, Eduarda C.,Cassamale, Tatiana B.,Carvalho, Diego B.,Bosquiroli, Lauriane S. S.,Ojeda, Mariáh,Ximenes, Thalita V.,Matos, Maria F. C.,Kadri, M?nica C. T.,Baroni, Adriano C. M.,Arruda, Carla C. P.
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- Rapid Access to Benzofuran-Based Natural Products through a Concise Synthetic Strategy
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A concise strategy is described for the synthesis of ailanthoidol (1), egonol (2), homoegonol (3), demethoxyegonol (4), demethoxyhomoegonol (5), and stemofuran A (6). This approach involves a Pd-catalysed domino cyclization/coupling process using triarylbismuth reagents for the generation of the benzofuran core. Subsequent structural modifications then give the final targets. The high yielding synthesis of the recently isolated natural products egonol-9(Z)-12(Z)-linoleate (2a), 7-demethoxyegonol-9(Z)-12(Z)-linoleate (4a), and 7-demethoxy-egonol-9(Z)-oleate (4b) are also reported.
- Rao, Maddali L. N.,Murty, Venneti N.
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p. 2177 - 2186
(2016/05/09)
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- A Fourfold Benzodehydroannuleno-Fused Porphyrazine
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Four benzodehydroannulene subunits were implemented on a dibenzoquinoxalinopoprhyrazine core using efficient palladium-mediated alkyne coupling and oxidative acetylene coupling on phenanthrene dione precursors. Despite the significant amount of strain in system, as evidenced by X-ray analysis of an immediate precursor, porphyrazine assembly leads to an extended model for N-doped graphyne with photosensitizing properties.
- K?rte, Fabian,Bruhn, Clemens,Faust, Rüdigger
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supporting information
p. 1620 - 1624
(2015/06/30)
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- Aerobic oxidative bromination of arenes using an ionic liquid as both the catalyst and the solvent
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A method for the bromination of alkoxy-substituted benzenes and naphthalenes was developed by using the residual oxygen in the reaction tube as the oxidant, and [Bmim]NO3 (1-butyl-3-methylimidazolium nitrate) ionic liquid as both the catalyst and the solvent. No other reagent apart from the ionic liquid and molecular bromine was used in the reactions, and basically all the bromine atoms in the bromine source were transferred to the bromination products, showing that the presented protocol is highly atom economic and practical.
- Ren, Yun-Lai,Wang, Binyu,Tian, Xin-Zhe,Zhao, Shuang,Wang, Jianji
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supporting information
p. 6452 - 6455
(2015/11/16)
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- Columnar mesomorphism of fluorescent board-shaped quinoxalinophenanthrophenazine derivatives with donor-acceptor structure
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Quinoxalino[2′,3′:9,10]phenanthro[4,5-abc]phenazine (QPP) dyes have been studied as electron acceptor materials, fluorophores, and building blocks for self-organizing organic semiconductors. Condensation of tetraketopyrene with electron-rich diamino-terphenylene and -triphenylene derivatives generates new donor-acceptor QPP derivatives that display columnar mesomorphism over wide ranges of temperature; are fluorescent in solution, liquid crystal, and solid phases; and have electron acceptor properties. Also reported are the synthesis and properties of the first diamino-(tetraalkoxy) triphenylene as a valuable new synthon.
- Chen, Shuai,Raad, Farah S.,Ahmida, Mohamed,Kaafarani, Bilal R.,Eichhorn, S. Holger
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supporting information
p. 558 - 561
(2013/04/10)
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- Fast and efficient bromination of aromatic compounds with ammonium bromide and Oxone
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A highly efficient, rapid and regioselective protocol was developed for the ring bromination of aromatic compounds under mild conditions with ammonium bromide as a source of bromine source and Oxone (potassium peroxysulfate) as an oxidant. No metal catalyst or acidic additive is required. A variety of aromatic compounds, including methoxy, hydroxy, amino, and alkyl arenes, reacted smoothly to give the corresponding monobrominated products in good to excellent yields in very short reaction times. Moreover, dibromination of deactivated anilines to give the corresponding dibromides proceeded in high yields. Interestingly, 1-(2-naphthyl)ethanone provided a ring-brominated product. Georg Thieme Verlag Stuttgart . New York.
- Naresh, Mameda,Arun Kumar, Macharla,Mahender Reddy, Marri,Swamy, Peraka,Nanubolu, Jagadeesh Babu,Narender, Nama
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p. 1497 - 1504
(2013/06/27)
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- 2,3,10,11-Tetrahydroxytetraphenylene and its application in molecular recognition
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A rationally designed 2,3,10,11-tetrahydroxytetraphenylene (1) has been synthesized. Employing 1 as a building block, a structurally novel tweezer-like host 2 containing dibenzo-24-crown-8 moieties has been prepared. Host 2 showed excellent molecular-recognition ability toward paraquat (=1,1′-dimethyl-4, 4′-bipyridinium dichloride) derivative 3a to form a 1: 1 stable complex in solution. Copyright
- Cui, Jian-Fang,Chen, Chao,Gao, Xiang,Cai, Zong-Wei,Han, Jian-Wei,Wong, Henry N. C.
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p. 2604 - 2620
(2013/03/14)
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- PROCESS FOR PRODUCTION OF HYDROXYTYROSOL USING ORGANOMETALLIC COMPOUNDS
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Disclosed is a process for the production of a 4-(2-hydroxyalkyl)-1,2-benzenediol, comprising the steps of (a) providing protected 1,2-benzenediol having the 1,2-hydroxyl groups protected, (b) halogenating the protected 1,2-benzenediol to obtain a protected 4-halo-1,2-benzenediol having the 1,2-hydroxyl groups protected, (c) reacting, in the presence of a metal or organometallic compound, the protected 4-halo-1,2-benzenediol to protected 4-(2-hydroxyalkyl)-1,2-benzenediol having the 1,2-hydroxyl groups protected, and (d) deprotecting the protected 4-(2-hydroxyalkyl)-1,2-benzenediol to obtain the 4-(2-hydroxyalkyl)-1,2-benzenediol. Also disclosed is the use of 1,2-benzenediol for the production of hydroxytyrosol.
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Page/Page column 11-12
(2012/02/02)
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- In situ acidic carbon dioxide/water system for selective oxybromination of electron-rich aromatics catalyzed by copper bromide
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Carbon dioxide, being one of the major greenhouse gases responsible for global warming, its atmospheric level grows ever faster since the beginning of industrial era. Great efforts have been devoted to developing versatile technologies/processes to adjust and manipulate the rapid growth of CO 2 emission. Besides CO2 capture and storage/sequestration (CCS) to control its emission, chemical utilization of the captured CO 2 (CCU) emerges to be a rational technique for economical benefits as well as environmental concerns. As for the aim of CO2 utilization, an environmentally benign CO2/water reversible acidic system was developed for the copper (II)-catalyzed selective oxybromination of electron-rich aromatics without the need of any conventional acid additive and organic solvent. Notably, up to 95% yields of the bromination products were attained with good regio-selectivity when cupric bromide was used as the catalyst and lithium bromide as a cheap and easy handling bromine source under supercritical CO2. The catalytic system worked well for electron-rich aromatics including ethers, sulfides and mesitylene. Carbonic acid in situ formed from CO2 and water is supposed to act as the proton donator in the Bronsted acid-promoted reaction. Notably, CO2 in this study serves as a reaction medium and a promoter in conjunction with water and also provides safe environment for aerobic reactions. Given with excellent reaction efficiency as well as no need of neutralization disposal, this process thus represents an environmentally friendly approach for aerobic bromination of aromatics with essential reduction of CO2 emission as well as an economically beneficial way for application of captured CO2.
- Liu, An-Hua,Ma, Ran,Zhang, Meng,He, Liang-Nian
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- Brominated methanes as photoresponsive molecular storage of elemental Br2
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The photochemical generation of elemental Br2 from brominated methanes is reported. Br2 was generated by the vaporization of carbon oxides and HBr through oxidative photodecomposition of brominated methanes under a 20 W low-pressure mercury lamp, wherein the amount and situations of Br2 generation were photochemically controllable. Liquid CH 2Br2 can be used not only as an organic solvent but also for the photoresponsive molecular storage of Br2, which is of great technical benefit in a variety of organic syntheses and in materials science. By taking advantage of the in situ generation of Br2 from the organic solvent itself, many organobromine compounds were synthesized in high practical yields with or without the addition of a catalyst. Herein, Br2 that was generated by the photodecomposition of CH2Br2 retained its reactivity in solution to undergo essentially the same reactions as those that were carried out with solutions of Br2 dissolved in CH 2Br2 that were prepared without photoirradiation. Furthermore, HBr, which was generated during the course of the photodecomposition of CH2Br2, was also available for the substitution of the OH group for the Br group and for the preparation of the HBr salts of amines. Furthermore, the photochemical generation of Br2 from CH2Br2 was available for the area-selective photochemical bleaching of natural colored plants, such as red rose petals, wherein Br2 that was generated photochemically from CH 2Br2 was painted onto the petal to cause radical oxidations of the chromophoric anthocyanin molecules. The generation of Br 2 from brominated methanes occurred upon photoirradiation under O2. The solutions that contained elemental Br2 were useful for the synthesis of organobromine compounds and the macroscopic photochemical bleaching of colored plants. Copyright
- Kawakami, Kazumitsu,Tsuda, Akihiko
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p. 2240 - 2252
(2012/11/06)
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- In situ acidic carbon dioxide/ethanol system for selective oxybromination of aromatic ethers catalyzed by copper chloride
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An environmentally benign carbon dioxide/ethanol reversible acidic system was developed for the copper(II)-catalyzed regioselective oxybromination of aromatic ethers without the need of any conventional acid additive and organic solvent. Good to excellent yields together with very good regioselectivity were achieved when easily available cupric chloride dihydrate was used as catalyst and lithium bromide as the cheap and easy-to-handle bromine source under supercritical carbon dioxide conditions. Notably, the catalytic system worked well for a wide range of aromatic ethers including sulfides, resulting in the formation of the mono-brominated products in high yields and exclusive regioselectivity. The alkylcarbonic acid in situ formed from ethanol and carbon dioxide is assumed to play the crucial role in the Braonsted acid-promoted reaction, which could probably act as the proton donator, and was studied employing in situ FT-IR technique under carbon dioxide pressure by monitoring the vibration shift of the hydroxy group of ethanol. Given with excellent bromine atom efficiency as well as no need of neutralization in waste disposal, this approach thus represents a greener pathway for the aerobic bromination of aromatic ethers. A possible catalytic cycle for the in situ alkylcarbonic acid-assisted oxybomination and the effect of supercritical carbon dioxide, i.e., activation of alcohol and enhancement of mass transfer are also discussed. Copyright
- Liu, An-Hua,He, Liang-Nian,Hua, Fang,Yang, Zhen-Zhen,Huang, Cheng-Bin,Yu, Bing,Li, Bin
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experimental part
p. 3187 - 3195
(2012/01/06)
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- Synthesis of the novel ligand tris-(3,4-dimethoxylphenyl) phosphine and its catalytic performance in 1-dodecene hydroformylation
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Tris-(3,4-dimethoxylphenyl)phosphine (TDMOPP) was synthesized and used as a ligand for the homogenous hydroformylation of 1-dodecene. The effects of the P/Rh molar ratio and reaction temperature on the activity and regioselectivity were investigated. The results showed that the activity of TDMOPP was about two times higher than that of the traditional triphenylphosphine at a low P/Rh and temperature.
- Yuan, Maolin,Fu, Haiyan,Li, Ruixiang,Chen, Hua,Li, Xianjun
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experimental part
p. 1093 - 1097
(2011/02/21)
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- Silver-catalysed protodecarboxylation of carboxylic acids
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A silver-based catalyst system has been discovered that effectively promotes the protodecarboxylation of various carboxylic acids at temperatures of 80-120 °C - more than 50 °C below those of the best known copper catalysts. The Royal Society of Chemistry 2009.
- Goossen, Lukas J.,Linder, Christophe,Rodriguez, Nuria,Lange, Paul P.,Fromm, Andreas
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supporting information; experimental part
p. 7173 - 7175
(2010/03/25)
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- Predicting the structure of supramolecular dendrimers via the analysis of libraries of AB3 and constitutional isomeric AB2 biphenylpropyl ether self-assembling dendrons
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The synthesis of 4′-hydroxy-4-biphenylpropionic, 3′,4′- dihydroxy-4-biphenylpropionic, 3′,5′-dihydroxy-4-biphenylpropionic, and 3′,4′,5′-trihydroxy-4-biphenylpropionic methyl esters via three efficient and modular strategies including one based on Ni-catalyzed borylation and sequential cross-coupling is reported. These building blocks were employed in a convergent iterative approach to the synthesis of one library of 3,4,5-trisubstituted and two libraries of constitutional isomeric 3,4- and 3,5-disubstituted biphenylpropyl ether dendrons. Structural and retrostructural analysis of supramolecular dendrimers revealed that biphenylpropyl ether dendrons self-assemble and self-organize into the same periodic lattices and quasi-periodic arrays observed in previously reported libraries, but with larger dimensions, different mechanisms of self-assembly, and improved solubility, thermal, acidic, and oxidative stability. The different mechanisms of self-assembly led to the discovery of two new supramolecular structures. The first represents a new banana-like lamellar crystal with a four layer repeat. The second is a giant vesicular sphere self-assembled from 770 dendrons that exhibits an ultrahigh molar mass of 1.73 × 106 g/mol. Thus, the enhanced size of the self-assembled structures constructed from biphenylpropyl ether dendrons permitted for the first time discrimination of various molecular mechanisms of spherical self-assembly and elaborated a continuum between small filled spheres and very large hollow spheres that is dictated by the primary structure of the dendron. The comparative analysis of libraries of biphenylpropyl ether dendrons with the previously reported libraries of benzyl-, phenylpropyl-, and biphenyl-4-methyl ether dendrons demonstrated biomimetic self-assembly wherein the primary structure of the dendron and to a lesser extent the structure of its repeat unit determines the supramolecular tertiary structure. A "nanoperiodic table" of self-assembling dendrons and supramolecular dendrimers that allows the prediction of the general features of tertiary structures from primary structures was elaborated.
- Rosen, Brad M.,Wilson, Daniela A.,Wilson, Christopher J.,Peterca, Mihai,Won, Betty C.,Huang, Chenghong,Lipski, Linda R.,Zeng, Xiangbing,Ungar, Goran,Heiney, Paul A.,Percec, Virgil
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supporting information; experimental part
p. 17500 - 17521
(2010/03/25)
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- Regioselective copper-catalyzed chlorination and bromination of arenes with O2 as the oxidant
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Electron-rich aromatic C-H bonds undergo regioselective chlorination and bromination in the presence of CuX2, LiX (X = Cl, Br) and molecular oxygen. Preliminary mechanistic insights suggest that the bromination and chlorination reactions proceed by different pathways.
- Yang, Lujuan,Lu, Zhan,Stahl, Shannon S.
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supporting information; experimental part
p. 6460 - 6462
(2010/03/04)
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- Copper(II) bromide: A simple and selective monobromination reagent for electron-rich aromatic compounds
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Copper(II) bromide was found to be a simple and efficient reagent for monobromination of electron-rich aromatic compounds at room temperature. The reaction proceeded smoothly with phenols, aryl alkyl ethers, and aromatic amines to afford the corresponding monobrominated product selectively in moderate to good yields. Copyright Taylor & Francis Group, LLC.
- Bhatt, Suchitra,Nayak, Sandip K.
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p. 1381 - 1388
(2008/02/01)
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- METHOD FOR PRODUCING 4-HALOCATECHOL COMPOUND
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Disclosed is a method for producing a 4-halocatechol compound, which is characterized in that a catechol compound is reacted with 1,3-dihalo-5,5-dimethylhydantoin. Also disclosed are a high-purity 4-chloromethylenedioxybenzene which is characterized in that the methylenedioxybenzene content is not more than 0.5% by mass and the 4,5-dichloromethylenedioxybenzene content is not more than 0.5% by mass, and a method for producing such a high-purity 4-chloromethylenedioxybenzene.
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Page/Page column 9-10
(2008/06/13)
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- Preparation of isobenzofurandiones by flash vacuum pyrolysis involving retro-Diels-Alder expulsion of ethylene and concomitant C-O cleavage of methoxy or ethylenedioxy groups
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Flash vacuum pyrolysis (fvp) of a number of substrates, prepared by hydrogenating adducts derived from dimethoxy- or ethylenedioxy-substituted benzynes and furan, affords isobenzofurandiones through retro-Diels-Alder expulsion of ethylene and C-O bond cleavage of the methoxy or ethylenedioxy groups. The parent isobenzofuran-4,5-dione is reactive and undergoes two-fold conjugate addition of water to afford 3,4-dihydroxybenzene-1,2-dicarboxaldehyde.
- Slamet, Riskiono,Wege, Dieter
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p. 12621 - 12628
(2008/03/14)
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- Site directed nuclear bromination of aromatic compounds by an electrochemical method
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Direct bromination of a wide range of aromatic compounds possessing electron-donating groups, such as methoxy, hydroxy or amino groups, have been carried out by two-phase electrolysis. This electrochemical method results in high yields (70-98%) of monobromo compounds and usually with high regioselectivity (>95%) for the para position.
- Raju,Kulangiappar,Anbu Kulandainathan,Uma,Malini,Muthukumaran
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p. 4581 - 4584
(2007/10/03)
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- Sodium nitrite-catalyzed oxybromination of aromatic compounds and aryl ketones with a combination of hydrobromic acid and molecular oxygen under mild conditions
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A novel and efficient catalytic system for the oxybromination of aromatic compounds and aryl ketones utilizing a combination of aqueous hydrobromic acid and molecular oxygen in the presence of sodium nitrite under mild conditions has been developed. The newly developed catalytic system utilizes cheap and readily available reactants, exhibits high bromine atom economy and releases only innocuous water as the by-product.
- Zhang, Guofu,Liu, Renhua,Xu, Qing,Ma, Lixin,Liang, Xinmiao
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p. 862 - 866
(2007/10/03)
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- Grindstone chemistry: (Diacetoxyiodo)benzene-mediated oxidative nuclear halogenation of arenes using NaCl, NaBr or I2
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A technique of "Grindstone chemistry" is applied to the solvent-free halogenation of arenes with NaCl, NaBr or I2 using (diacetoxyiodo)benzene as the oxidant. Improved yields and higher purities of the products are observed compared with those from established methods.
- Karade,Tiwari,Huple,Siddiqui
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p. 366 - 368
(2007/10/03)
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- Exploring and expanding the structural diversity of self-assembling dendrons through combinations of AB, constitutional isomeric AB2, and AB3 biphenyl-4-methyl ether building blocks
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General, efficient and inexpensive methods for the synthesis of dendritic building blocks methyl 3′,4′-dihydroxybiphenyl-4-carboxylate, 3′,5′-dihydroxybiphenyl-4-carboxylate, and methyl 3′,4′,5′-trihydroxybiphenyl-4-carboxylate were elaborated. In all syntheses the major step involved an inexpensive NiII-catalyzed Suzuki cross-coupling reaction. These three building blocks were employed together with methyl 4′-hydroxybiphenyl-4-carboxylate in a convergent iterative strategy to synthesize seven libraries containing up to three generations of 3′,4′-, 3′,5′-, and 3′,4′,5′-substituted biphenyl-4-methyl ether based amphiphilic dendrons. These dendrons self-assemble into supramolecular dendrimers that self-organize into periodic assemblies. Structural and retrostructural analysis of their assemblies demonstrated that these dendrons self-assemble into hollow and non-hollow supramolecular dendrimers exhibiting dimensions of up to twice those reported for architecturally related dendrons based on benzyl ether repeat units. These new dendrons expand the structural diversity and demonstrate the generality of the concept of self-assembling dendrons based on amphiphilic arylmethyl ethers.
- Percec, Virgil,Holerca, Marian N.,Nummelin, Sami,Morrison, John J.,Glodde, Martin,Smidrkal, Jan,Peterca, Mihai,Rosen, Brad M.,Uchida, Satoshi,Balagurusamy, Venkatachalapathy S. K.,Sienkowska, Monika J.,Heiney, Paul A.
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p. 6216 - 6241
(2008/12/22)
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- Novel bromination method for anilines and anisoles using NH 4Br/H2O2 in CH3COOH
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A simple, efficient, regioselective, environmentally safe, and economical method for the oxybromination of anilines and anisoles without catalyst is reported. The electrophilic substitution of bromine generated in situ from ammonium bromide as a bromine source and hydrogen peroxide as an oxidant for the first time.
- Krishna Mohan,Narender,Srinivasu,Kulkarni,Raghavan
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p. 2143 - 2152
(2007/10/03)
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- Efficient halogenation of aromatic systems using N-halosuccinimides in ionic liquids
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A simple, rapid and highly regioselective green protocol has been developed for the halogenation of aromatic systems with N-halosuccinimides using room temperature ionic liquids (ILs) as novel and recyclable reaction media to produce the corresponding halogenated aromatic compounds in high to quantitative yields. N-Halosuccinimides show enhanced reactivity in ionic liquids thereby reducing the reaction times dramatically and improving the yields substantially.
- Yadav,Reddy,Reddy,Basak,Narsaiah
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- Mild and regioselective oxidative bromination of aromatic compounds using ammonium bromide and oxone
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The selective mono-bromination of various activated aromatic compounds is reported using in situ generated bromine from NH4Br as a bromine source and oxone as an oxidant for the first time.
- Narender,Mohan, K.V.V. Krishna,Kulkarni,Raghavan
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p. 597 - 598
(2007/10/03)
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- An efficient chemo and regioselective oxidative nuclear bromination of activated aromatic compounds using lithium bromide and ceric ammonium nitrate
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A mild, efficient and highly chemo- and regioselective method for the bromination of electron rich aromatic molecules has been developed by electrophilic substitution of Br+, which was generated in situ from LiBr using ceric ammonium nitrate as the oxidant. Free aromatic amines remained unaffected under the reaction conditions.
- Roy, Subhas Chandra,Guin, Chandrani,Rana, Kalyan Kumar,Maiti, Gourhari
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p. 6941 - 6942
(2007/10/03)
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- Environment friendly regiospecific bromination of aromatic ethers by N- bromosuccinimide in presence of montmorillonite
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Reaction of methoxybenzenes and naphthalenes with N-bromosuccinimide in presence of montmorillonite clay (K10) affords excellent yields of regiospecifically brominated products under mild conditions in the absence of solvent.
- Perumal,Vijayabaskar,Gomathi,Selvaraj
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p. 603 - 604
(2007/10/03)
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- Kaolin-assisted Aromatic Chlorination and Bromination
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Moist kaolin catalyses the regioselective and high-yielding chlorination and bromination of C6H5OR (R = C1-C8 alkyl. Bu1, allyl, cyclohexyl, benzyl) to 4-XC6H4OR (X = Cl and Br, respectively) with NaCl02 and Mn(acac)3 in CH2Cl2 in the absence and presence of NaBr, respectively, under mild and neutral conditions.
- Hirano, Masao,Monobe, Hiroyuki,Yakabe, Shigetaka,Morimoto, Takashi
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p. 662 - 663
(2007/10/03)
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- Regioselective aromatic monobromination of alkyl phenyl ethers with NaClO2, NaBr, Mn(acac)3, and Montmorillonite K10 in dichloromethane
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Regioselective and high-yielding nuclear monobromination of aromatic ethers can be accomplished with a combination of NaClO2, NaBr, and Mn(acac)3 catalyst in dilchloromethane under mild and neutral conditions with the aid of Montmorillonite K10.
- Hirano, Masao,Yakabe, Shigetaka,Monobe, Hiroyuki,Morimoto, Takashi
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p. 669 - 676
(2007/10/03)
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- Nuclear monobromination of alkyl phenyl ethers with NaClO2, NaBr, Mn(acac)3, and moist silica gel in aprotic solvent
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Nuclear monobromination of aromatic ethers can be achieved with a NaClO2/NaBr/Mn(acac)3 catalyst/silica gel system in dichloromethane in regioselective and high-yielding manner under mild conditions.
- Hirano, Masao,Monobe, Hiroyuki,Yakabe, Shigetaka,Morimoto, Takashi
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p. 1463 - 1470
(2007/10/03)
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- Electrophilic Aromatic Bromination Using Bromodimethylsulfoniuin Bromide Generated in Situ
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It has been shown that bromodimethylsulfonium bromide, generated in situ by treating dimethyl sulfoxide with aqueous hydrobromic acid, is a milder and more selective reagent for electrophilic aromatic bromination than elemental bromine.
- Majetich, George,Hicks, Rodgers,Reister, Steven
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p. 4321 - 4326
(2007/10/03)
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- The Bromination of Phenolic Methyl Ethers with Hydrogen Bromide using Sodium Tungstate and Hydrogen Peroxide as Oxidant
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Sodium tungstate has been found to be an effective catalyst for the nuclear bromination of some aromatic methyl ethers using hydrogen bromide in glacial acetic acid and hydrogen peroxide as the oxidant.
- Bezodis, Paul,Hanson, James R.,Petit, Philippe
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p. 334 - 335
(2007/10/03)
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- EFFICIENT SYNTHESIS AND BIOLOGICAL PROPERTIES OF NEW BENZOPENTATHIEPINS
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New 6,7-dimethoxybenzopentathiepin and 6-(2-aminoethyl)benzopentathiepin, which are partial structures of varacin, were synthesized from 1,2-dimethoxybenzene and 1,2-benzenedithiol respectively.
- Sato, Ryu,Ohyama, Tetsuya,Ogawa, Satoshi
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p. 893 - 896
(2007/10/02)
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- A Mild Selective Monobromination Reagent System for Alkoxybenzenes; N-Bromosuccinimide-Silica Gel
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The monobromination of alkoxybenzenes with N-bromosuccinimide catalyzed by silica gel in carbon tetrachloride occurred preferentially at the para-position. m-t-Butylmethoxybenzene yielded 4-bromo-3-t-butyl-1-methoxybenzene with a selectivity of 74percent even in the presence of a bulky substituent at the meta-position.
- Konishi, Hisatoshi,Aritomi, Katsutomo,Okano, Tamon,Kiji, Jitsuo
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p. 591 - 593
(2007/10/02)
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