- Synthesis of symmetrical dinitro-and diamino-substituted Troeger's base analogues
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This report describes a new synthetic approach to symmetrical diamino-substituted Troeger's base analogues, allowing the synthesis of 1,7-, and 4,10-diamino derivatives with no additional substituents and of 3,9-diamino derivative with methyl groups in the 1-, 4-, 7-and 10-positions. The synthesis uses regioselective nitration of dihalo-substituted-or tetrahalo-substituted Troeger's bases followed either by hydrogenation of the nitro functions accompanied by removal of halogen atoms or alternatively by chemoselective reduction of nitro groups to obtain the dihalo-diamino- substituted Troeger's base analogues. The 2,8-diamino derivatives, not accessible by this approach, can be prepared by Buchwald-Hartwig amination of the 2,8-dibromo-substituted Troeger's bases.
- Sturala, Jiri,Cibulka, Radek
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p. 7066 - 7074
(2013/02/21)
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- Halide ion trapping of nitrenium ions formed in the Bamberger rearrangement of N-arylhydroxylamines. Lifetime of the parent phenylnitrenium ion in water
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The data of p-aminophenol, the product of Bamberger rearrangement, Were analyzed by a mechanism involving rate-limiting formation of the appropriate arylnitrenium ion followed by product-determining steps in involving trapping by the solvent or by the added halide. The possibility that a portion of the halide-trapped products were derived from a pre-association mechanism was also include. Kinetic analyses then produced kBr:kw and kCl:kw ratios for two limiting cases, one involving pre-association with an equilibrium constant Kas = 0.3, and one ignoring pre-association. From an azide:water ratio (kAz:kw) previously determined for the 2,6-dimethylphenylnitrenium, kBr was concluded to lie in the range (4-5) × 109 M-1 s-1 for all of the nitrenium ions of this study. This range for kBr then led to kw values of (1-2) × 109 s-1 (2,5-Me2), (2-3) × 109 s-1 (2-Me), and (4-8) × 109 s-1 (parent and 2-Cl), where the ranges reflect uncertainties in the exact value of kBr and in the contribution from pre-association. The lifetime of the parent phenylnitrenium ion in water at one molar ionic strength is concluded to lie in the range 125-250 ps.
- Fishbein,McClelland
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p. 1321 - 1328
(2007/10/03)
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