- Direct Azidation of Phenols
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Direct azidation of phenols was developed. By treating chloroimidazolinium chloride 1b and sodium azide with phenol in the presence of a secondary amine in methoxyethanol, ortho-azidation of phenol was achieved.
- Kitamura, Mitsuru,Murakami, Kento,Koga, Tatsuya,Eto, Takashi,Ishikawa, Akihiro,Shimooka, Hirokazu,Okauchi, Tatsuo
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- Synthesis of Diazoquinones and Azidophenols via Diazo-Transfer Reaction of Phenols
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The first efficient diazo-transfer reaction of phenols is described. o-Quinone diazides (diazoquinones) were prepared from phenols in high yields by the diazo-transfer reaction using 2-azido-1,3-bis(2,6-diisopropylphenyl)imidazolium hexafluorophosphate (IPrAP, 2-PF6), which is a safe and stable crystalline. The reaction efficiently proceeded in methanol in the presence of a base. Phenols substituted with electron-donating groups reacted more smoothly than those having electron withdrawing groups. Reactive phenols were diazotized by IPrAP with iPr2NH as a base, and low reactive phenols were diazotized with N,N-dimethyl-4-aminopyridine (DMAP). Furthermore, the formed diazoquinones reacted with sodium azide in 2-methoxyethanol and afforded the corresponding azidophenol in high yields.
- Eto, Takashi,Kitamura, Mitsuru,Konai, Kazushige,Okauchi, Tatsuo,Shimooka, Hirokazu,Takahashi, Shuhei
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supporting information
(2022/05/20)
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- ELECTROPHILIC AZIDIZING AGENT OR DIAZOTIZING AGENT
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PROBLEM TO BE SOLVED: To provide a novel electrophilic azidizing agent that is safe without explosibility, capable of azidizing a nucleophilic compound in an electrophilic manner. SOLUTION: The present invention provides an azide imidazolium derivative re
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Paragraph 0075-0078
(2019/07/31)
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- The hydrolysis of 4-acyloxy-4-substituted-2,5-cyclohexadienones: Limitations of aryloxenium ion chemistry
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The title compounds serve as potential precursors to aryloxenium ions, often proposed, but primarily uncharacterized intermediates in phenol oxidations. The uncatalyzed and acid-catalyzed decomposition of 4-acetoxy-4-phenyl-2,5-cyclohexadienone, 2a, generates the quinol, 3a. 18O-Labeling studies performed in 16O-H2O, and monitored by LC/MS and1 13C NMR spectroscopy that can detect 18O-induced chemical shifts on 13C resonances, show that 3a was generated in both the uncatalyzed and acid-catalyzed reactions by C alkyl-O bond cleavage consistent with formation of an aryloxenium ion. Trapping with N3- and Br- confirms that both uncatalyzed and acid-catalyzed decompositions occur by rate-limiting ionization to form the 4-biphenylyloxenium ion, 1a. This ion has a shorter lifetime in H2O than the corresponding nitrenium ion, 7a (12 ns for 1a, 300 ns for 7a at 30 °C). Similar analyses of the product, 3b, of acid- and base-catalyzed decomposition of 4-acetoxy-4-methyl-2,5-cyclohexadienone, 2b, in 18O-H2O show that these reactions are ester hydrolyses that proceed by Cacyl-O bond cleavage processes not involving the p-tolyloxenium ion, 1b. Uncatalyzed decomposition of the more reactive 4-dichloroacetoxy-4-methyl-2,5-cyclohexadienone, 2b′, is also an ester hydrolysis, but 2b′ undergoes a kinetically second-order reaction with N3- that generates an oxenium ion-like substitution product by an apparent SN2′ mechanism. Estimates based on the lifetimes of 1a, 7a, and the p-tolylnitrenium ion, 7b, and the calculated relative stabilities of these ions toward hydration indicate that the aqueous solution lifetime of 1b is ca. 3-5 ps. Simple 4-alkyl substituted aryloxenium ions are apparently not stable enough in aqueous solution to be competitively trapped by nonsolvent nucleophiles.
- Novak, Michael,Glover, Stephen A.
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p. 8090 - 8097
(2007/10/03)
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