- Preparation of carbazole and dibenzofuran derivatives by selective bromination on aromatic rings or benzylic groups with N-bromosuccinimide
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N-Bromosuccinimide (NBS), a bromine source, has been used to study the bromination of toluidine and cresols systematically to clarify the underlying mechanism and the orientation effect. It has been found that bromination of toluidine and cresols which possess electron-donating NH2/OH with NBS gives electrophilic aromatic substitution products quickly instead of the desired benzylic bromination products. In contrast, when the electronic effect of the substituted groups is reversed, only the benzylic bromination products are gained. Based on this methodology, several potential AChE inhibitors, such as 2-methoxy-5-(benzylamino)methyl-dibenzofuran, 3-bromo-2-methoxy-5-methyl-9H- carbazole, 3,6-dibromo-2-methoxy-5-methyl-9H-carbazole, and 5-(bromomethyl)-2- methoxy-9H-(phenylsulfonyl)-carbazole have been synthesized.
- Fang, Lei,Zhang, Haun,Fang, Xubin,Gou, Shaohua,Cheng, Lin
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p. 635 - 641
(2014/06/23)
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- Synthesis of isomers of rhodamine 575 and rhodamine 6G as new laser dyes
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Two new laser dyes of the rhodamine family, substituted at C-1 and C-8, were prepared by condensation of phthalic anhydride with 3-ethylamino-5- methylphenol. Two methodologies have been investigated for the preparation of the latter.
- Scala-Valero, Claudine,Doizi, Denis,Guillaumet, Gerald
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p. 4803 - 4806
(2007/10/03)
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- The efficient and regioselective synthesis of the naphthoquinone core of streptovaricin U
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The efficient and regioselective synthesis of the naphthoquinone core of streptovaricin U 1 via the Diels-Alder reaction of 1-methoxy-2-methyl-3-trimethylsilyloxybuta-1,3-diene 5 with the 2,6-dibromo-3-methyl-1,4-benzoquinone 6 is described.
- Miyashita, Masaaki,Yamasaki, Takahiro,Shiratani, Tomonori,Hatakeyama, Susumi,Miyazawa, Masahiro,Irie, Hiroshi
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p. 1787 - 1788
(2007/10/03)
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- Synthesis and inhibitory activity of bromoquinone derivatives
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2,5 Dibromo-3-methyl-6-isopropyl-1,4-benzoquinone has been reported inhibitory to b6-f and b-c1 complexes [Malkin, R. (1977) Biochim. Biophys. Acta., 501, 552-554]. In this paper, four classes of the analogues are synthesized. They were 5-bromo-3-methyl, 3-bromo-2-methoxy-5-methyl, 2,5-dibromo-3-methyl, and 3,5-dibromo-2-methyl derivatives with the side chain -(CH2)nH of N=5,7,9,11 and 13 at position 6. Dibromo compounds are usually more inhibitory in the mitochondrial ubiquinol cytochrome c reductase; the maximal inhibition was usually with 9 methylene in a functional group.
- Gu, Lianquan,Liu, Cuihua,Xu, Jingxing,King, Tsoo E.
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p. 3199 - 3210
(2007/10/02)
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- Halogenation Using Quaternary Ammonium Polyhalides. IV. Selective Bromination of Phenols by Use of Tetraalkylammonium Tribromides
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Reaction of phenols with calculated amounts of benzyltrimethylammonium tribromide or tetrabutylammonium tribromide in dichloromethane-methanol for 0.5-1 h under mild conditions gave, selectively, the objective mono-, di-, or tribromophenols in good yields.
- Kajigaeshi, Shoji,Kakinami, Takaaki,Okamoto, Tsuyoshi,Nakamura, Hiroko,Fujikawa, Masahiro
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p. 4187 - 4189
(2007/10/02)
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- Electrophilic Substitution with Rearrangement. Part 9. Dienones derived from Brominations of o-, m-, and p-Cresol
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Regiospecific protodebromination of ring-substituted bromophenols derived from 2-, 3-, or 4-methylphenol can be effected by heating them with aqueous hydrogen iodide; the synthetic scope of this reaction has been explored.These di- and poly-bromophenols can generally be converted by further bromination in aqueous acetic acid into dienones , which have now been shown to have the 4-bromo-2,5-dienone rather than the 2-bromo-3,5-dienone structure.The rearrangemens of these dienones to ring-substituted polybromophenols by treatment with sulfuric acid have been investigated; where more than one product is formed, the regioselectivity differs from that prevailing in the corresponding direct bromination of the phenol with liquid bromine.The alternative rearrangements of these dienones in aprotic solvents with and without illumination have been compared with results obtained by reaction of methylphenols with bromine under the same conditions.Characteristic differences between the behaviours of 2-, 3-, and 4-methyl-substituted compounds reflect the specific reactions available to the particular dienones.
- Brittain, Judith M.,Mare, Peter B. D. de la,Newman, Paul A.
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