- Iron-catalyzed arene C-H hydroxylation
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The sustainable, undirected, and selective catalytic hydroxylation of arenes remains an ongoing research challenge because of the relative inertness of aryl carbon-hydrogen bonds, the higher reactivity of the phenolic products leading to over-oxidized by-products, and the frequently insufficient regioselectivity. We report that iron coordinated by a bioinspired L-cystine-derived ligand can catalyze undirected arene carbon-hydrogen hydroxylation with hydrogen peroxide as the terminal oxidant. The reaction is distinguished by its broad substrate scope, excellent selectivity, and good yields, and it showcases compatibility with oxidation-sensitive functional groups, such as alcohols, polyphenols, aldehydes, and even a boronic acid. This method is well suited for the synthesis of polyphenols through multiple carbon-hydrogen hydroxylations, as well as the late-stage functionalization of natural products and drug molecules.
- Cheng, Lu,Wang, Huihui,Cai, Hengrui,Zhang, Jie,Gong, Xu,Han, Wei
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- Method for promoting iron-catalyzed oxidation of aromatic compound carbon - hydrogen bond to synthesize phenol by ligand
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The method comprises the following steps: iron is used as - a catalyst metal; a sulfur-containing amino acid or cystine-derived dipeptide is a ligand; and under the common action of hydrogen peroxide as an oxidizing agent, an aromatic compound is synthesized to prepare a phenol. Under the action of an acid as an accelerant and hydrogen peroxide as an oxidizing agent, the aryl carbon - hydrogen bond is directly hydroxylated to form a phenolic compound, and the method for preparing the phenol by the catalytic oxidation reaction has a plurality of advantages. The reaction raw materials, the oxidant and the promoter are wide in source, low in price, environment-friendly and good in stability. The aromatic compound carbon - hydrogen bonds directly participate in the reaction to react in one step to form phenol. The reaction condition is mild, the functional group compatibility and the application range are wide. The reaction selectivity is good; under the optimized reaction conditions, the target product separation yield can reach 85%.
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Paragraph 0054-0055; 0127
(2021/09/21)
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- Synthesis of natural product-like polyprenylated phenols and quinones: Evaluation of their neuroprotective activities
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Twenty-seven natural product-like polyprenylated phenols and quinones were synthesized and their neuroprotective activity was tested using human monoamine oxidase B (MAO-B) and SH-SY5Y cells. Eight compounds inhibited MAO-B (IC50 values 25 μM
- Kamauchi, Hitoshi,Oda, Takumi,Horiuchi, Kanayo,Takao, Koichi,Sugita, Yoshiaki
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- Understanding the regioselectivity in the oxidative condensation of catechins using pyrogallol-type model compounds
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Catechins are found in many foods, including tea. These compounds are bioactive. Previous studies have shown that catechins form dimers on oxidation, and there seem to be distinct regioselective effects. However, the dimerization mechanism and regioselectivity are not well understood. Therefore, we investigated the oxidation of four pyrogallol-type model compounds of epigallocatechin (EGC) having various substituents with 1 equiv of copper chloride and 30% dioxane in water. Compounds having 2C-2C or 2C-4C bonds in the B-ring were obtained in different product ratios. Comparison of the oxidation rates of each compound revealed that the model compounds having an oxygen atom corresponding to the 1-position of the C-ring of EGC underwent slow oxidation. In addition, using density functional theory calculations, we found that the highest occupied molecular orbital energies of these compounds were higher than those of the others. Further, the 2C-2C-bonded oxidation product having an A-ring and an oxygen atom at the C-ring 1-position was confirmed to have the highest thermodynamic stability. From these results, it is suggested that the regioselective condensation reaction of the catechin B-ring is related to interactions between the A-rings, as indicated by earlier studies, and the presence of oxygen at the 1-position of the C-ring in EGC.
- Yanase, Emiko,Ochiai, Yuto,Hirose, Sayumi
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supporting information
p. 12359 - 12366
(2020/11/10)
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- Unusual polycyclic fused product by oxidative enzymatic dimerisation of 5-methylpyrogallol catalysed by horseradish peroxidase/H2O2
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During investigations on the peroxidase-catalysed oxidation of polyhydroxylated monoaromatic substrates such as 5-methylpyrogallol, we observed a spectacular dimerisation proceeding by dearomatisation in contrast with most common reaction patterns involvi
- Bouges, Hélène,Calabro, Kevin,Thomas, Olivier P.,Antoniotti, Sylvain
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- Synthesis method of substituted pyrogallols
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The invention relates to a synthesis method of substituted pyrogallols, belonging to the field of organic synthesis. The method comprises the following steps: by using aryloxy pyridines as a raw material, carrying out reaction in an organic solvent at 60-
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Paragraph 0013-0014; 0018
(2017/03/14)
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- PROCESS FOR STRAIGHTENING KERATIN FIBRES WITH A HEATING MEANS AND DENATURING AGENTS
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The invention relates to a process for straightening keratin fibres, comprising: (i) a step in which a straightening composition containing at least two denaturing agents is applied to the keratin fibres, (ii) a step in which the temperature of the keratin fibres is raised, using a heating means, to a temperature of between 110 and 250° C.
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- Evaluation of the pharmacophoric motif of the caged Garcinia xanthones
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The combination of unique structure and potent bioactivity exhibited by several family members of the caged Garcinia xanthones, led us to evaluate their pharmacophore. We have developed a Pd(0)-catalyzed method for the reverse prenylation of catechols tha
- Chantarasriwong, Oraphin,Cho, Woo Cheal,Batova, Ayse,Chavasiri, Warinthorn,Moore, Curtis,Rheingold, Arnold L.,Theodorakis, Emmanuel A.
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supporting information; experimental part
p. 4886 - 4894
(2010/02/15)
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- Synthesis of crown ethers related to ubiquinones
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Crown ethers in which the two methoxy groups of ubiquinone-0 (2,3-dimethoxy-5-methyl-1,4-benzoquinone) are replaced by oligoethylene glycol bridges have been obtained in five straightforward steps in 35-40% overall yield from 5-methylpyrogallol. A Fremy salt oxidation of a phenolic precursor is used in the final step. The further elaboration of crown ether analogues of ubiquinone-2 was achieved by enol geranylation of cyclopentadiene adducts of the former quinones and subsequent retro-Diels-Alder reaction. The Claisen rearrangement of 2,2-dimethoxy-5-methylphenyl allyl ethers and related crown ethers affords ortho- and para-allyl-substituted phenols (3:1) that are oxidized to give bisnorubiquinone derivatives and their ortho-quinone isomers. All new compounds are characterized by high resolution NMR and mass spectrometry.
- Merz,Rauschel
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p. 797 - 802
(2007/10/02)
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- Production of organic compounds
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Pyrogallol, and analogues thereof having an alkyl, carboxy or alkoxycarbonyl substituent in the benzene ring, and their salts, are prepared by oxidizing, preferably by hydrogen peroxide, the corresponding compounds in which 1 or 2 of the OH groups are replaced by --COR5 groups where R5 represents hydrogen, alkyl or phenylalkyl. The production of intermediates is also described and some of these are novel.
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