- A Four-Step Synthesis of (±)-γ-Lycorane via Pd0-Catalyzed Double C(sp2)-H/C(sp3)-H Arylation
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An expedient synthesis of lycorine alkaloids is reported using a palladium(0)-catalyzed double C-X/C-H arylation as the key step. The selectivity of this reaction was controlled through the judicious choice of the two halogen atoms, and its generality was
- Rocaboy, Ronan,Dailler, David,Baudoin, Olivier
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- Direct Synthesis of Paracetamol via Site-Selective Electrochemical Ritter-type C-H Amination of Phenol
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The synthesis of paracetamol still relies on multistep protocols involving the utilization of a stoichiometric amount of oxidizing/reducing or other corrosive agents. Herein we report a regioselective electrochemical Ritter-type reaction at the C(sp2)-H of unprotected phenol toward the environmentally benign and direct synthesis of paracetamol. The reaction proceeds under exogenous oxidant- and catalyst-free conditions. The protocol is scalable, can be deployed to a variety of phenols, and offers a sustainable alternative for the synthesis of paracetamol.
- Banerjee, Prabal,Saha, Debarshi,Taily, Irshad Maajid
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supporting information
(2022/04/07)
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- Redox-Neutral Selenium-Catalysed Isomerisation of para-Hydroxamic Acids into para-Aminophenols
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A selenium-catalysed para-hydroxylation of N-aryl-hydroxamic acids is reported. Mechanistically, the reaction comprises an N?O bond cleavage and consecutive selenium-induced [2,3]-rearrangement to deliver para-hydroxyaniline derivatives. The mechanism is studied through both 18O-crossover experiments as well as quantum chemical calculations. This redox-neutral transformation provides an unconventional synthetic approach to para-aminophenols.
- Chuang, Hsiang-Yu,Schupp, Manuel,Meyrelles, Ricardo,Maryasin, Boris,Maulide, Nuno
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p. 13778 - 13782
(2021/03/31)
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- 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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- A novel CAN-SiO2-mediated one-pot oxidation of 1-keto-1,2,3,4-tetrahydrocarbazoles to carbazoloquinones: Efficient syntheses of murrayaquinone A and koeniginequinone A
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One-pot oxidations of substituted 1-keto-1,2,3,4-tetrahydrocarbazoles (1) to carbazole-1,4-quinones (2) are efficiently carried out by CAN-SiO 2-mediated reaction. This generalized protocol was successfully extended to the synthesis of two naturally occurring carbazoloquinones: murrayaquinone A (2b) and koeniginequinone A (2g). A plausible mechanism for this novel reaction involves formation of a 9-hydroxy-2,3,4,9-tetrahydro-1H- carbazole-1-one followed by rearrangement to 1-hydroxycarbazole derivatives, which are further oxidized by cerium (IV) to carbazoloquinones.
- Chakraborty, Suchandra,Chattopadhyay, Gautam,Saha, Chandan
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experimental part
p. 331 - 338
(2011/06/19)
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- Bisacetamide hydrochloride: A chemoselective and inexpensive N-acetylating reagent for aminophenols
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A facile and chemoselective acetylation of aminophenols using bisacetamide hydrochloride under conventional heating and microwave irradiation has been developed. Also, a rapid method for the microwave-assisted preparation of aminophenols is described herein.
- Peng, Yanqing,Song, Gonghua,Ding, Fang
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p. 2021 - 2023
(2007/10/03)
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- Introduction of a hydroxy group at the para position and N-iodophenylation of N-arylamides using phenyliodine(III) bis(trifluoroacetate)
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The reaction of anilides with phenyliodine(III) bis(trifluoroacetate) (PIFA) in trifluoroacetic acid (TFA), TFA-CHCl3, or hexafluoroisopropyl alcohol (HFIP) is described. When the acyl group of the anilide is highly electronegative, such as trifluoroacetyl, or the phenyl group is substituted with an electron-withdrawing group, the 4-iodophenyl group is transferred from PIFA to the amide nitrogen to afford acetyldiarylamines. On the other hand, when the acyl group contains an electron-donating function, such as 4-methoxyphenyl, or the phenyl group is substituted with an electron-donating group, a trifluoroacetoxy group is transferred to the para position of the anilide aromatic ring. This group is hydrolyzed during workup to produce the corresponding phenol.
- Itoh, Naoki,Sakamoto, Takeshi,Miyazawa, Etsuko,Kikugawa, Yasuo
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p. 7424 - 7428
(2007/10/03)
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- Comparative Toxicities and Analgesic Activities of Three Monomethylated Analogues of Acetaminophen
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Three monomethylated derivatives of 4'-hydroxyacetanilide (acetaminophen) were prepared in order to compare their cytotoxic potential and analgesic activity with that of acetaminophen.Only 4'-hydroxy-methylacetanilide (N-methylacetaminophen) was devoid of cytotoxic effects to hepatic tissue of mice.Results of comparative tissue distribution studies and metabolism studies both in vivo and in vitro in mice indicate that the disposition of N-methylacetaminophen is similar to that of acetaminophen except that it is not oxidized to a toxic metabolite.In contrast, 3'-methyl-4'-hydroxyacetanilide (3-methlacetaminophen) is as hepatotoxic as acetaminophen in mice while 2'-methyl-4'-hydroxyacetanilide (2-methylacetaminophen) is less hepatotoxic.The analgesic potency of the analogues seems to parallel their hepatotoxic potential, and both activities parallel the oxidation potentials in this series of compounds.
- Harvison, Peter J.,Forte, Anthony J.,Nelson, Sidney D.
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p. 1737 - 1743
(2007/10/02)
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- Hydrolysis of N-(Sulfonatooxy)-p-acetotoluidide: Solution Chemistry of Models for Carcinogenic Metabolites of Aromatic Amides
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The hydrolysis reactions of the title compound, a model for the carcinogenic metabolites of polycyclic aromatic amides, were investigated over the pH range 1.0-8.0 by UV spectroscopic methods, product analyses, HPLC, and 1H NMR.This compound is unique among the N-(sulfonatooxy)acetanilides that have been studied to date in that over most of the pH range examined it exhibits non-first-order reaction kinetics.Product analyses indicate that, like the other N-(sulfonatooxy)acetanilides, the hydrolysis of this compound involves N-O bond cleavage, and the kinetics of the N-O bond cleavage process are consistent with a mechanism that includes generation of nitrenium ion-sulfate ion pairs.Four transient species, 9-12, were generated in sufficient quantity to be detected during the hydrolysis reaction.On the basis of isolated decomposition products and kinetic and spectral data obtained during the course of the hydrolysis reaction, the intermediate 9 was identified as 4-hydroxy-4-methylcyclohexa-2,5-dien-1-one N-acetylimine, while 10 and 11 were identified as the isomeric cis- and trans-N-acetyl-2-amino-5,6-dihydroxy-5-methylcyclohexa-1,3-dienes.These species are analogous to materials isolated by Gassman and Granrud from the methanolysis reactions of the methanesulfonate ester of N-hydroxy-p-acetotoluidide.The fourth intermediate, 12, has been tentatively identified as 4-(sulfonatooxy)-4-methylcyclohexa-2,5-dien-1-one.The pH dependence of the hydrolysis reactions of 9 and 10 have also been thoroughly investigated.Both are subject to acid catalysis of hydrolysis and give rise to a number of products.
- Novak, Michael,Roy, Ajit K.
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p. 571 - 580
(2007/10/02)
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- Hydrolysis of N-(Pivaloyloxy)-p-acetotoluidide: N-O Bond Cleavage Reactions of a Model Proximate Carcinogen
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The hydrolysis reactions of N-(pivaloyloxy)-p-acetotoluidide (1a), a model for the carcinogenic metabolites of polycyclic aromatic amides, were investigated by a combination of UV spectroscopy, product analyses, and HPLC methods at 70 deg C over the pH range 2.0-8.0.Under these conditions 1a undergoes exclusive N-O bond cleavage to yield products characteristic of processes involving nitrenium ion pairs.In many ways the reactions of 1a in aqueous solution parallel those of the analogous sulfuric acid ester, 1b.However, two unique products, 3-(pivaloyloxy)-4-methylacetanilide (2b) and 4-acetotoluidide (9), which have no analogues in the reactions of 1b under these conditions, were isolated.The first-order rate constant for the decomposition of 1a, which is independent of pH and buffer composition, is (380 +/- 60)-fold less than the corresponding rate constant for 1b under the same conditions.The characteristics of the hydrolysis reaction of 1a are considerably different from those of the N-acetoxy-N-arylacetamides which undergo a considerable amount of acyl transfer under similar conditions.These results indicate that pivalic acid esters may be more appropriate models for the proximate carcinogens derived from N-hydroxy-N-arylacetamides than are the acetic acid estrs if, indeed, nitrenium ions are the ultimate carcinogens.
- Novak, Michael,Roy, Ajit K.
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p. 4884 - 4888
(2007/10/02)
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