- Double functionalization of 2-amino-2′-hydroxy-1,1′-biaryls: Synthesis of 4-nitro-dibenzofurans and benzofuro-indoles
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Several substituted 2′-amino-biphenyl-2-ols were synthesized. The mild and TM-free double functionalization: nitration and cycloetherification of 2′-amino-biphenyl-2-ols have been achieved for the synthesis of functionalized 4-nitro-dibenzofurans utilizing NaNO2 in TFA and water. Interestingly, nitration of phenol ring was observed along with the dibenzofuran ring formation in the one-pot synthesis. The position of the nitro group in several dibenzofurans is also established by X-ray crystal structure studies. Further functionalization of the obtained 4-nitro-dibenzofurans has been carried into 3-nitro-terphenyl-2-ol, novel benzofuro-indoles, and amino-dibenzofurans. The mechanistic understanding on double functionalization of 2′-amino-biphenyl-2-ols suggests that reaction proceeds by a combination of nitration of the phenol ring followed by Sandmeyer reaction for dibenzofuran ring formation.
- Kumar, Amit,Sattar, Moh.,Verma, Ajay,Dara, Ankit,Kumar, Sangit
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Read Online
- Regioselective Preparation of 2- and 3-Nitrodibenzofurans by the Direct Nitration of Dibenzofuran
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Nitration of dibenzofuran with nitric acid in trifluoroacetic acid gave 3-nitrodibenzofuran selectively under very mild conditions.In contrary, the Friedel-Crafts type nitration using alkyl nitrates and aluminium chloride in nitromethane gave 2-nitrodibenzofuran as the main product.
- Keumi, Takashi,Yamada, Hideyo,Takahashi, Hisakazu,Kitajima, Hidehiko
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Read Online
- Quinoline Ligands Improve the Classic Direct C?H Functionalisation/Intramolecular Cyclisation of Diaryl Ethers to Dibenzofurans
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The C?H functionalisation approach to the synthesis of dibenzofurans is hampered by a number of problems. Herein we describe the evolution of a cheap, bench stable quinoline ligand, which obviates most of the current limitations and allows for a high yielding synthesis of a range of valuable dibenzofurans. Dibenzofurans are important motifs in natural products and compounds with wide biological activity.
- Mackey, Katrina,Jones, David J.,Pardo, Leticia M.,McGlacken, Gerard P.
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p. 495 - 498
(2021/01/12)
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- Synthesis of Dibenzofurans by Cu-Catalyzed Deborylative Ring Contraction of Dibenzoxaborins
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An efficient transformation of dibenzoxaborins to dibenzofurans by deborylative ring contraction was achieved under mild conditions using a copper catalyst. The method showed a broad substrate scope enabling the preparation of various dibenzofurans, including those bearing a functional group. The ready availability of various dibenzoxaborins enhances the utility of this method, as demonstrated by the regiodivergent synthesis of dibenzofurans.
- Sumida, Yuto,Harada, Ryu,Sumida, Tomoe,Johmoto, Kohei,Uekusa, Hidehiro,Hosoya, Takamitsu
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supporting information
p. 6687 - 6691
(2020/09/02)
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- 3-(Ethoxycarbonyl)-1-(5-methyl-5-(nitrosooxy)hexyl)pyridin-1-ium cation: A green alternative to tert-butyl nitrite for synthesis of nitro-group-containing arenes and drugs at room temperature
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Due to their remarkable properties, task-specific ionic liquids have turned out to be progressively popular over the last few years in the field of green organic synthesis. Herein, for the first time, we report that a new task-specific nitrite-based ionic liquid such as 3-(ethoxycarbonyl)-1-(5-methyl-5-(nitrosooxy)hexyl)pyridin-1-ium bis(trifluoromethanesulfonyl)imides (TS-N-IL) derived from biodegradable ethyl nicotinate indeed acted as an efficient and eco-friendly reagent for the synthesis of highly valuable nitroaromatic compounds and drugs including nitroxynil, tolcapone, niclofolan, flutamide, niclosamide and nitrazepam. The bridging of an ionic liquid with nitrite group not only increases the yield and rate of direct C[sbnd]N bond formation reaction but also allows easy product separation and recyclability of a byproduct. Nonvolatile nature, easy synthesis, merely stoichiometric need and mildness are a portion of the extra focal points of TS-N-IL while contrasted with tert-butyl nitrite an outstanding and highly-flammable reagent utilized largely in organic synthesis.
- Chaudhary, Renu,Natarajan, Palani,Rani, Neetu,Sakshi,Venugopalan, Paloth
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supporting information
(2019/12/30)
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- NOVEL OXIME ESTER COMPOUND AND PHOTORESIST COMPOSITION CONTAINING THE SAME
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The present invention relate to an oxime ester compound represented by chemical formula A, and to a photoresist composition containing the same. The X, R1, R2 and R5 of the formula A are as described in the description of the invention. The present inventnion aims to provide the oxime ester compound as a novel photoinitiator which can be used as a photoresist composition.COPYRIGHT KIPO 2018
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Paragraph 0103-0106
(2019/02/13)
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- Microwave-Promoted Pd-Catalyzed Synthesis of Dibenzofurans from Ortho-Arylphenols
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ortho-Aryl phenols, synthesized via protecting group free Suzuki–Miyaura coupling of ortho-halophenols and arene boronic acids, undergo a cyclization to dibenzofurans via oxidative C–H activation. The reaction proceeds under microwave irradiation in short reaction times using catalytic amounts of Pd(OAc)2 without additional ligands.
- Schmidt, Bernd,Riemer, Martin
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p. 1287 - 1297
(2017/03/27)
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- One-Pot Assembly of Fused Heterocycles via Oxidative Palladium-Catalyzed Cyclization of Arylols and Iodoarenes
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A one-pot, two-step cyclization reaction of iodoarenes with diversified arylols, including 4-hydroxyquinoline, quinolinone, 4-hydroxypyridine and phenol, has been developed. By using this palladium-catalyzed formal tandem O-arylation, dehydrogenative cross-coupling reaction, a variety of biologically significant fused benzo[4,5]furo heterocycles and dibenzofurans were quickly assembled in high yields with excellent regioselectivity. Notably, the efficient one-pot reaction led to the heterocycles via sequential oxidation, iodination, isomerization and cyclization steps without purification of any reaction intermediates.
- Hong, Fenglin,Chen, Yingwen,Lu, Beili,Cheng, Jiajia
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p. 353 - 357
(2016/02/12)
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- One pot synthesis of diarylfurans from aryl esters and PhI(OAc)2 via palladium-associated iodonium ylides
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The example of palladium-catalyzed intermolecular cyclization for the synthesis of various diarylfurans in which one of the aromatic rings originates from the phenolic part of the starting ester and the other one from PhI(OAc)2 has been reported. The reaction is carried out through two steps: the rearrangement of palladium-associated iodonium ylides to form o-iodo diaryl ether and then palladium catalyzed intramolecular direct arylation. This reaction can tolerate a variety of functional groups and is alternative or complementary to the previous methods for the synthesis of diarylfurans.
- Bao, Yong-Sheng,Bao, Agula,Bao, Zhaorigetu,Jia, Meilin,Baiyin, Menghe
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supporting information
p. 4179 - 4182
(2015/04/14)
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- Synthesis of Dibenzofurans via C-H Activation of o-Iodo Diaryl Ethers
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An efficient method for the synthesis of dibenzofuran from o-iododiaryl ether using reusable Pd/C under ligand-free conditions has been developed. Synthesis of o-iododiaryl ether was achieved in one pot through sequential iodination and O-arylation of phenol under mild reaction conditions.
- Panda, Niranjan,Mattan, Irshad,Nayak, Dinesh Kumar
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p. 6590 - 6597
(2015/10/06)
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- ORGANIC ELECTROLUMINESCENT ELEMENT MATERIAL HAVING SILICON-CONTAINING FOUR MEMBERED RING STRUCTURE, AND ORGANIC ELECTROLUMINESCENT ELEMENT
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Provided are a material for an organic electroluminescent element formed of a silicon-containing four-membered ring compound, and an organic electroluminescent element using the material. The material for an organic electroluminescent element is formed of
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Paragraph 0090
(2014/08/19)
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- Ultrasound-promoted intramolecular direct arylation in a capillary flow microreactor
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An intramolecular direct arylation of various aryl bromides was performed using ultrasonic irradiation and a continuous flow capillary microreactor. The present procedure provided a higher functional group tolerance, ligand-free, milder reaction condition
- Zhang, Lei,Geng, Mei,Teng, Peng,Zhao, Dan,Lu, Xi,Li, Jian-Xin
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p. 250 - 256
(2012/04/23)
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- Cu-catalyzed oxidative C(sp2)-H cycloetherification of o-arylphenols for the preparation of dibenzofurans
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A new process involving copper-catalyzed aerobic C(sp2)-H activation, followed by cycloetherification, has been developed. This reaction serves as a direct method for the preparation of multisubstituted dibenzofurans starting with o-arylphenols. The presence of a strong para-electron-withdrawing group (e.g., NO2) on the phenol is essential for the success of the reaction.
- Zhao, Jiaji,Wang, Yong,He, Yimiao,Liu, Lanying,Zhu, Qiang
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p. 1078 - 1081
(2012/03/27)
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- One-pot Synthesis of Dibenzofurans via SNAr and Subsequent Ligand-free Palladium-catalyzed Intramolecular Aryl-aryl Cross-coupling Reactions under Microwave Irradiation
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An efficient one-pot synthesis of dibenzofurans, via SNAr reaction of aryl halides and ortho-bromophenols in the presence of anhydrous K2CO 3 and subsequent ligand-free palladium-catalyzed intramolecular aryl-aryl cross-coupling cyclization under microwave irradiation, is described.
- Che, Zhiping,Xu, Hui
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p. 833 - 836
(2011/10/05)
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- PHOSPHORESCENT EMITTERS
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Compounds including a ligand with a dibenzo-fused 5-membered ring substituent are provided. In particular, the compounds may be iridium complexes including imidazole coordinated to the dibenzo-substituted ligand. The dibenzo-fused 5-membered ring moiety of the ligand may be twisted or minimally twisted out of plane with respect to the rest of the ligand structure. The compound may be used in organic light emitting devices, particularly as emitting dopants in blue devices. Devices comprising the compounds may demonstrate improved stability while maintaining excellent color.
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- Synthesis of dibenzofurans via palladium-catalyzed phenol-directed C-H activation/C-O cyclization
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A practical, Pd(0)/Pd(II)-catalyzed reaction was developed for phenol-directed C-H activation/C-O cyclization using air as an oxidant. The turnover-limiting step of the process was found to be C-O reductive elimination instead of C-H activation. This reaction can tolerate a variety of functional groups and is complementary to the previous methods for the synthesis of substituted dibenzofurans.
- Xiao, Bin,Gong, Tian-Jun,Liu, Zhao-Jing,Liu, Jing-Hui,Luo, Dong-Fen,Xu, Jun,Liu, Lei
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supporting information; experimental part
p. 9250 - 9253
(2011/08/06)
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- Formation of dibenzofurans by flash vacuum pyrolysis of aryl 2-(allyloxy)benzoates and related reactions
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Flash vacuum pyrolysis (FVP) of aryl 2-(allyloxy)benzoates 5 and of the corresponding aryl 2-(allylthio)benzoates 6 at 650°C, gives dibenzofurans 19 and dibenzothiophenes 20, respectively. The mechanism involves generation of phenoxyl (or thiophenoxyl) radicals by homolysis of the O-allyl (or S-allyl) bond, followed by ipso attack at the ester group, loss of CO2 and cyclisation of the resulting aryl radical. Synthetically, the procedure works well for p-substituted substrates, which lead to 2-substituted dibenzofurans 19b-f (73-90%) and dibenzothiophenes 20b-c (90-94%). Little selectivity is shown in the cyclisation of m-substituted substrates and competing interactions of the radical with the substituent - and ipso-attack - complicate the pyrolyses of o-substituted substrates. FVP of related radical precursors including 2-(allyloxy)phenyl benzoates 43 gave no dibenzofurans, whereas 2-(allyloxy-5-methyl)azobenzene 44 gave a much reduced yield. No carbazoles were obtained by FVP of 4-methylphenyl 2-(allylamino)benzoate 42.
- Black, Michael,Cadogan,McNab, Hamish
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experimental part
p. 2961 - 2967
(2010/09/06)
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- Intramolecular Pd(II)-catalyzed oxidative biaryl synthesis under air: Reaction development and scope
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(Figure Presented) New reaction conditions for intramolecular palladium(II)-catalyzed oxidative carbon-carbon bond formation under air are described. The use of pivalic acid as the reaction solvent, instead of acetic acid, results in greater reproducibility, higher yields, and broader scope. This includes the use of electron-rich diarylamines as illustrated in the synthesis of three naturally occurring carbazole products: Murrayafoline A, Mukonine, and Clausenine. A variety of side products have also been isolated, casting light on competing reaction pathways and revealing new reactivity with palladium(II) catalysis.
- Liegault, Benoit,Lee, Doris,Huestis, Malcolm P.,Stuart, David R.,Fagnou, Keith
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p. 5022 - 5028
(2008/09/21)
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- Synthesis of dibenzofurans directly from aryl halides and ortho-bromophenols via one-pot consecutive SNAr and intramolecular palladium-catalyzed aryl-aryl coupling reactions
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A series of dibenzofurans were efficiently and conveniently synthesized via one-pot consecutive C(sp2)-O bond formation reaction (SNAr) in the presence of anhydrous K2CO3, followed by C(sp 2)-C(sp2) b
- Xu, Hui,Fan, Ling-Ling
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experimental part
p. 1496 - 1498
(2009/10/16)
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- Electroreduction of 2- and 3-Chlorodibenzofuran in Deuterated Methanol
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The cathodic reduction of dibenzofuran (2), 2-chlorodibenzofuran (4), and 3-chlorodibenzofuran (1) in deuterated methanol is investigated. The Birch-type reduction product 1,4-dibenzofuran (3) is formed from 1 via 2, whereas 2-chloro-1,4-dihydrodibenzofuran (5) is obtained as by-product besides 3 from 4 as starting compound. Deuterium is only incorporated into the reduction products if CH3OD or CD3OD but not if CD3OH are used. This observation is strongly indicative of a polar mechanism involving protonation rather than a radical mechanism with hydrogen atom abstraction to be operative.
- Voss, Juergen,Waller, Edgar,Kraenke, Petra
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p. 430 - 436
(2007/10/03)
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- Photochemical nitration by tetranitromethane part XXX. Product isolation and identification in the photochemical reaction of dibenzofuran
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The photolysis of the charge-transfer complex of dibenzofuran (1) and tetranitromethane in either dichloromethane or acetonitrile gives t-2-nitro-r-1-trinitromethyl-1,2-dihydrodibenzofuran (4), the epimeric 4-nitro-1-trinitromethyl-1,4-dihydrodibenzofurans 5 and 7, the epimeric 4-hydroxy-1-trinitromethyl-1,4-dihydrodibenzofurans 6 and 8, 3-trinitromethyldibenzofuran (13), and the four isomeric nitrodibenzofurans 9-12. The five adducts 4-8 are formed via attack by trinitromethanide ion at C1 of the dibenzofuran radical cation, while 3-trinitromethyldibenzofuran is formed by decomposition of an adduct, itself formed via initial attack of trinitromethanide ion at C3 of the dibenzofuran radical cation. The regiochemistry of attack of trinitromethanide ion on the radical cation of the non-alternant dibenzofuran system is in keeping with earlier theoretical predictions. In 1,1,1,3,3,3-hexafluoropropan-2-ol solution the analogous photolysis of the charge-transfer complex of dibenzofuran (1) and tetranitromethane gives only the four nitrodibenzofurans 9-12, the attack of trinitromethanide ion on the radical cation of dibenzofuran being suppressed by the solvent. X-Ray crystal structures are reported for compounds 4, 6 and 13, compound 6 representing the first hydroxytrinitromethyl adduct to be unambiguously assigned this structure. Acta Chemica Scandinavica 1996.
- Butts, Craig P.,Eberson, Lennart,Hartshorn, Michael P.,Robinson, Ward T.,Wood, Bryan R.
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p. 587 - 595
(2007/10/03)
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- Photochemical Nitration by Tetranitromethane. III. On the Anomalous Nitration and Oxidative Substitution of Dibenzofuran and a Novel Test of the Shaik-Pross Model of Radical Cation Reactivity
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The photochemical reaction of dibenzofuran and tetranitromethane in dichloromethane gives predominantly nitro/trinitromethyl adducts and only a small amount of nitro-substitution products.The adducts originate from the reaction between photochemically produced trinitromethanide ion and (dibenzofuran)cation radical, followed by reaction of the trinitromethyl-substituted cyxlohexadienyl radical with NO2.The main sites of attack of trinitromethanide ion are the 1- and the 3-positions.The adducts rapidly eliminate nitroform in the presence of a hindered base.Thus photolysis with with such a base present gives directly a mixture containing predominantly 2- and 4-nitrodibenzofuran.The unexpected attack of trinitromethanide at the 3-position of (dibenzofuran)cation radical is also found in more typical oxidative substitution reactions, such as acetoxylation and cyanation.This isomer distribution is distinctly different from that of electropholic substitution in dibenzofuran (attack at the 2-position), a non-alternant conjugated system.The Shaik-Pross treatment of the radical cation/nucleophile elementary step predicts that the spin density of the corresponding triplet should govern the isomer distribution, and CASSCF calculations show that (dibenzofuran)cation radical then should react predominantly in the 3-position.Thus the electrophilic reactivity of the radical cations of non-alternant systems constitutes a novel test of the configuration mixing model.It is also concluded that the unusual substitution pattern of dibenzofuran with respect to electrophilic nitration is due to incursion of the nitrous acid catalyzed (NAC) reaction.
- Eberson, Lennart,Hartshorn, Michael P.,Radner, Finn,Merchan, Manuela,Roos, Bjoern O.
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p. 176 - 183
(2007/10/02)
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- Positional Reactivity of Dibenzofuran in Electrophilic Substitutions
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Isomer distributions of dibenzofuran (DBF) in Friedel-Crafts acylations, Friedel-Crafts alkylations, and nitrations have been determined.The 2- and 3-positions of DBF represents most of the total reactivity.However, the ratio of 2- to 3-isomers greatly varied, depending on the nature of the electrophile.The positional reactivities have been found to be in the following sequence: 2- > 3- > 1- > 4-positions for Friedel-Crafts acylations, Friedel-Crafts benzylations, and nitrations with alkyl nitrate/Lewis acid or nitronium tetrafluoroborate.The ratios for acylations varied over a range from 13.1 to 2.9, while for benzylations and nitrations from 2.0 to 1.0.In contrast, for nitrations of DBF with nitric acid a different reactivity order was found: 3- > 2- > 1- > 4-, with the ratio varying from 0.8 to 0.03 depending on the nature of solvents used.The selectivity for the 3-substitution increased with increase in nitronium ion-like character of nitrating reagents.In particular, nitration with nitric acid in dichloromethane gave mostly 3-nitro-DBF (95percent of the four possible isomeric mixture).The charge-transfer nitration with tetranitromethane under the UV irradiation has shown a similar isomer distribution to that in nitration with nitric acid.The MNDO calculations predicts that the late transition-state model (by ?-complex) favors reactions at the 2-position while the early transition-state model (by HOMO electron density) leads to the 3-substitution.
- Keumi, Takashi,Tomioka, Naoto,Hamanaka, Kozo,Kakihara, Hirohito,Fukishima, Masahiko,et al.
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p. 4671 - 4677
(2007/10/02)
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- A Remarkable Difference of the Positional Selectivity in Electrophilic Aromatic Substitution of Dibenzofuran between the Classical ?-Complex and Charge-Transfer Mechanisms
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Electrophilic nitration of dibenzofuran with nitric acid by a charge-transfer mechanism occurs exclusively at the 3-position and on the other hand, substitution at the 2-position predominates in the acylation, in which a classical ?-complex mechanism is important.
- Keumi, Takashi,Hamanaka, Kozo,Hasegawa, Haruo,Minamide, Naoki,Inoue, Yoshinori,Kitajima, Hidehiko
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p. 1285 - 1288
(2007/10/02)
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- PALLADIUM-CATALYSED CYCLISATION OF 2-SUBSTITUTED HALOGENOARENES BY DEHYDROHALOGENATION
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Cyclodehydrohalogenation mediated by various palladium catalysts and solvents with different bases (the most generally satisfactory system being palladium(II) acetate in NN-dimethylacetamide (DMA) with sodium carbonate as base) has been examined as a route to some heterocyclic systems.Whereas dehydrogenative cyclisation processes require stoichiometric amounts of palladium(II) reagent, the present procedure involves only catalytic amounts (0.1 molar proportion, or less), of palladium compound.The preparation of dibenzofuran, carbazole, fluorenone, 6H-dibenzothiazine-5,5-dioxide, 6H-dibenzopyran and benzofuranopyridine derivatives is described.The cyclisation of 3-benzamido-2-chloropyridine to 6-hydroxybenzonaphthiridine illustrates the regiospecificity of the process.
- Ames, D.E.,Opalko, A.
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p. 1919 - 1926
(2007/10/02)
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- Intramolecular Cyclization of Aryloxenium Ions. C-O-C and C-C Bond Formation. A Novel Ortho Effect
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o-Aryloxenium ions undergo intramolecular C-O-C bond formation readily as shown by the cyclizations yielding dibenzofurans. m-Aryloxenium ions cyclize via C-C bond formation provided the molecule can adopt the appropriate conformation for ring closure to occur.When an oxygen atom is ortho to the ?-aryl cation center, cyclization to form five- or six-membered rings does not occur and this is attributed to an interaction between oxygen and the positive charge that imposes an unfavorible conformation for cyclization on the aryloxy or arylalkyloxy side chain.
- Abramovitch, Rudolph A.,Bartnik, Romuald,Cooper, Melanie,Dassanayake, Nissanke L.,Hwang, Hang-Yuong,et al.
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p. 4817 - 4818
(2007/10/02)
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