- Development of the radical C–O coupling reaction of phenols toward the synthesis of natural products comprising a diaryl ether skeleton
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Compounds comprising a diaryl ether skeleton exist among natural phenols. The diaryl ether skeleton is thought to be biosynthesized through the coupling of two or more phenols. It is an important structural feature in medicines and agrochemicals, and it is imperative to develop methods for constructing such skeletons in organic synthesis. However, by the synthesis method through the coupling of phenols, coupling occurs preferentially at the ortho-substituted carbon atom of phenols. In this study, various radical-generating reagents and conditions were investigated with the aim of developing a short-step construction method of the diaryl ether skeleton by the radical homo-coupling of two phenol molecules. In addition, cross-coupling reactions between radicals of 2,4,6-tri-tert-butylphenol and p-substituted phenol were conducted to synthesize eight C (ortho)–O coupling products. Based on the results, a computational chemical approach was employed to verify the cause of C (ortho)–O bond formation.
- Tanaka, Kumpei,Gotoh, Hiroaki
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- New method for the preparation of o-aryloxyphenols: Pummerer-type rearrangement of ano-hydroxyaryl sulfoxide
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A facile two-step preparation of o-aryloxyphenols is described in which the key step is the intramolecular trapping of an α-keto sulfonium salt prepared by Pummerer rearrangement of a symmetrical o-hydroxyaryl sulfoxide to give an orthoquinone mono(monoth
- Jung,Jachiet,Khan,Kim
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- Isolation of cross-coupling products in model studies on the photochemical modification of proteins by tiaprofenic acid
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To gain insight into the chemical nature of drug-induced photoallergy, model studies have been carried out on the photochemical modification of proteins by tiaprofenic acid. Irradiation of decarboxylated tiaprofenic acid (DTPA) in the presence of p-cresol leads to C-C- and C-O-connected p-cresol 'dimers', together with DTPA hydrodimers. The p-cresol-DTPA cross-coupling product was not detected in this reaction. However, a product of this type is formed using a more hindered phenol, such as 2,6-di-tert-butylphenol. Similar results are obtained when tiaprofenic acid (TPA) or its methyl ester are used as photosensitizers. The observed formation of 'dimers' can be related to protein photo-crosslinking, through the coupling of two tyrosine units. On the other hand, phenol-(D)TPA cross-coupling may be relevant to the understanding of drug-protein photobinding.
- Miranda, Miguel Angel,Perez-Prieto, Julia,Lahoz, Agustin,Morera, Isabel M.,Sarabia, Zaideth,Martinez-Manez, Ramon,Castell, Jose V.
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p. 497 - 502
(2007/10/03)
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