- Stepwise mechanism for the bromination of arenes by a hypervalent iodine reagent
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A mild, metal-free bromination method of arenes has been developed using the combination of bis(trifluoroacetoxy)iodobencene and trimethylsilyl bromide. In situ-formed dibromo(phenyl)-λ3-iodane (PhIBr2) is proposed as the reactive intermediate. This methodology using PIFA/TMSBr has been applied with success to a great number of substrates (25 examples). The treatment of mono-substituted activated arenes led to para-brominated products (2u-z) in excellent 83-96% yields. Density functional theory calculations indicate a stepwise mechanism involving a double bromine addition followed by a type II dyotropic reaction with concomitant re-aromatization of the six-membered ring.
- Arrieta, Ana,Cossío, Fernando P.,Granados, Albert,Shafir, Alexandr,Vallribera, Adelina
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p. 2142 - 2150
(2020/03/11)
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- Chemistry of polyhalogenated nitrobutadienes, part 11: Ipso-formylation of 2-chlorothiophenes under Vilsmeier-Haack conditions
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The regioselective ipso-formylation of electron-rich, 3,4-push-pull- substituted 2-chlorothiophenes under Vilsmeier-Haack conditions was performed in good yields. The synthetic scope of this new reaction was explored using various halothiophenes, chloroanilines, and 1-methyl-3-chloroindole. In comparison with their structural C-H analogs the chlorinated thiophenes, anilines, and the indole proved to be less reactive toward electrophilic attack by chloromethyleniminium salts.
- Vogt, Eva-Janina,Zapol'skii, Viktor A.,Nutz, Eva,Kaufmann, Dieter E.
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experimental part
p. 285 - 294
(2012/07/14)
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- Synthesis of 2,6-disubstituted and 2,3,6-trisubstituted anilines
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A number of 2,6-disubstituted and 2,3,6-trisubstituted anilines have been prepared via the selective para dehalogenation of the corresponding anilines. Modification of the substituents on the amino nitrogen demonstrates that the selectivity is derived from steric rather than electronic effects. The effects of the choice of formate hydrogen donor, Pd catalyst, solvent, and temperature upon the efficiency and selectivity of the dehalogenation are discussed.
- Pews,Hunter,Wehrmeyer
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p. 4809 - 4820
(2007/10/02)
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