- Site-Selective C?H Oxygenation via Aryl Sulfonium Salts
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Herein, we report a two-step process forming arene C?O bonds in excellent site-selectivity at a late-stage. The C?O bond formation is achieved by selective introduction of a thianthrenium group, which is then converted into C?O bonds using photoredox chemistry. Electron-rich, -poor and -neutral arenes as well as complex drug-like small molecules are successfully transformed into both phenols and various ethers. The sequence differs conceptually from all previous arene oxygenation reactions in that oxygen functionality can be incorporated into complex small molecules at a late stage site-selectively, which has not been shown via aryl halides.
- Sang, Ruocheng,Korkis, Stamatis E.,Su, Wanqi,Ye, Fei,Engl, Pascal S.,Berger, Florian,Ritter, Tobias
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supporting information
p. 16161 - 16166
(2019/11/03)
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- Hydroxylation of anilides by engineered cytochrome P450BM3
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Biocatalytic direct monohydroxylation of anilides has been achieved on preparative scale using mutant cytochrome P450BM3 enzymes. Representative mono- and disubstituted N-trifluoromethanesulfonyl anilides are shown to be converted in most cases to the corresponding 4-hydroxy derivatives, with substituent hydroxylation also occurring in two cases. By mutation variation, it is possible to achieve selective hydroxylation of either ring- or side-chain sites.
- O'Hanlon, Jack A.,Ren, Xinkun,Morris, Melloney,Wong, Luet Lok,Robertson, Jeremy
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supporting information
p. 8780 - 8787
(2017/11/03)
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- New insight on the mechanism of the catalytic hydrogenation of nitrobenzene to 4-aminophenol in CH3CN-H2O-CF3COOH as a reusable solvent system.
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The preparation of 4-aminophenol via hydrogenation of nitrobenzene in a single liquid phase has been carried in the presence of different precious metal catalysts. The liquid phase is composed of CH3CN-H 2O-CF3COOH, which can be easily distilled at low temperature, thus avoiding work-up operation. The yield of 4-aminophenol is in the range 45% and in the presence of sulfolane as promoter reaches almost 50%. The best result has been obtained in the presence of Pt/C as hydrogenation catalyst. The role of the solvent is strictly related to the selectivity to 4-aminophenol, since CH3CN decreases the hydrogenation activity compared to other solvent, CF3COOH promotes the formation of the desired product both via Bamberger rearrangement in solution as well by a surface catalyzed reaction, while H2O is responsible for 4-aminophenol formation in both reactions. Even though, nitrosobenzene and phenylhydroxylamine have not been observed, their reactivity suggest a complex pattern of reactions occurring either on the catalyst surface or in the solution. Indeed, formation of 4-aminophenol may occur both in solution, via acid catalyzed Bamberger rearrangement and on the catalyst surface by the formation of a surface Pt-nitrenium complex, which undergoes surface nucleophilic attack by H2O.
- Quartarone, Giuseppe,Ronchin, Lucio,Tosetto, Alice,Vavasori, Andrea
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p. 169 - 178
(2014/03/21)
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- Subphthalocyanines: Addressing water-solubility, nano-encapsulation and activation for optical imaging of B16 melanoma cells
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Water-soluble disulfonato-subphthalocyanines (SubPcs) or hydrophobic nano-encapsulated SubPcs are efficient probes for the fluorescence imaging of cells. 20 nm large liposomes (TEM and DLS) incorporated about 13% SubPc. Moreover, some of these fluorophores were found to be pH activatable.
- Bernhard, Yann,Winckler, Pascale,Chassagnon, Remi,Richard, Philippe,Gigot, lodie,Perrier-Cornet, Jean-Marie,Decrau, Richard A.
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supporting information
p. 13975 - 13978
(2015/02/19)
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- A thermally reversible temperature sensor based on polydiacetylene: Synthesis and thermochromic properties
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A novel temperature sensor based on polydiacetylene, displayed colorimetrically reversible properties in the range of 30 °C and 70 °C in solution. PVA film embedded PDA supramolecules displayed similar temperature reversibility.
- Chen, Xiaoqiang,Yoon, Juyoung
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experimental part
p. 194 - 198
(2011/09/20)
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- Synthesis of 5-substituted 2,3-dihydrobenzofurans in a one-pot oxidation/cyclization reaction
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Variously substituted 2,3-dihydrobenzofurans have been synthesized according to a sequential one-pot oxidation/cyclization procedure between para-aminophenol derivatives and an azadiene.
- Baragona, Fabien,Lomberget, Thierry,Duchamp, Christian,Henriques, Natali,Lo Piccolo, Eugenio,Diana, Patrizia,Montalbano, Alessandra,Barret, Roland
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experimental part
p. 8731 - 8739
(2011/12/02)
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- Trifluoroacetylation of amines with trifluoroacetic acid in the presence of trichloroacetonitrile and triphenylphosphine
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We developed a mild and convenient trifluoroacetylation process for amines using a combination of trichloroacetonitrile and triphenylphosphine. The reaction that we designed is applicable to the trifluoroacetylation of a wide variety of amines, including amines with stereogenic centers, which underwent trifluoroacetylation without racemization.
- Kim, Joong-Gon,Jang, Doo Ok
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scheme or table
p. 683 - 685
(2010/04/02)
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- Primary amine-functional benzoxazine monomers and their use for amide-containing monomeric benzoxazines
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Amino-functional benzoxazine monomers have been successfully prepared. Several routes have been applied to incorporate amino group into benzoxazine structure. These approaches include reduction of the corresponding nitro-functional benzoxazines and deprot
- Agag, Tarek,Arza, Carlos R.,Maurer, Frans H. J.,Ishida, Hatsuo
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experimental part
p. 2748 - 2758
(2011/10/09)
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- A one-pot procedure for trifluoroacetylation of arylamines using trifluoroacetic acid as a trifluoroacetylating reagent
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A convenient procedure for the preparation of aryl trifluoroacetamides from aryl amines is described that employs 2-4 M equiv of trifluoroacetic acid in refluxing xylene as a trifluoroacetylating agent. Addition of an amount of pyridine that is equimolar to the amount of trifluoroacetic acid present in the reaction mixture facilitates the trifluoroacetylation of rather basic arylamines.
- Ohtaka, Junpei,Sakamoto, Takeshi,Kikugawa, Yasuo
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experimental part
p. 1681 - 1683
(2009/09/05)
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- A new, convenient and selective 4-dimethylaminopyridine-catalyzed trifluoroacetylation of anilines with ethyl trifluoroacetate
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A new, convenient, and selective 4-dimethylaminopyridine-catalyzed trifluoroacetylation of anilines with ethyl trifluoroacetate is described. Anilines, containing other functional groups, e.g. alcohols, phenols, hindered secondary amines, and secondary anilines, are also selectively trifluoroacetylated in high yields under these newly developed conditions. (C) 2000 Elsevier Science Ltd.
- Prashad,Hu,Har,Repic,Blacklock
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p. 9957 - 9961
(2007/10/03)
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- Mechanisms of the photochemical rearrangement of diphenyl ethers
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The mechanism of the photochemical rearrangement of diphenyl ether (1a) was studied. Irradiation of 1a in ethanol gave 2-phenylphenol (2, 42%) and 4-phenylphenol (3, 11%) as rearrangement products, in addition to phenol (4, 30%) and benzene (5, 25%) as diffusion products. Cross-coupling experiments employing [2H10]1a demonstrated that the formation of 2- and 4-phenylphenol was an intramolecular process. Irradiation of 1a in benzene or in toluene gave biphenyls in good yields. The combined yields of rearrangement products (2 and 3) increased with increase of solvent viscosity, with a concomitant decrease in the formation of 4. All the results can be rationalized in terms of excitation of 1a to the singlet state and dissociation to a radical pair intermediate involving phenoxy and phenyl radicals. Intramolecular recombination of these radicals gives rearrangement products, and escape followed by hydrogen abstraction from the solvent gives diffusion products. When position 4 of 1a was occupied by an electron-donating substituent (1b-e), aryloxy-phenyl bond cleavage to give the corresponding rearrangement products prevailed over phenoxy-aryl bond cleavage. The opposite was the case for substrates with an electron-withdrawing substituent at position 4 (1h,i).
- Haga, Naoki,Takayanagi, Hiroaki
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p. 735 - 745
(2007/10/03)
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- The effect of fluorine substitution on the physicochemical properties and the analgesic activity of paracetamol
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The physicochemical properties and analgesic action of six fluorinated analogues of 4-hydroxyacetanilide (paracetamol) have been investigated. Fluorine substitution adjacent to the hydroxyl group increased lipophilicity and oxidation potential whilst substitution adjacent to the amide had little effect on lipophilicity but led to a greater increase in oxidation potential. Lack of coplanarity and conjugation of the amide group and aromatic ring was also apparent with the analogues that had fluorine in the 2 and 6 positions. Introduction of fluorine into the amide group of paracetamol increased the lipophilicity 4-fold and also increased the oxidation potential of paracetamol. ED50 values for analgesic activity in the phenylquinone-induced abdominal constriction test on male Swiss White mice showed that ring substitution by fluorine reduced activity, especially at the 2,6-positions. Introduction of fluorine into the amide group enhanced activity significantly. Correlation of the analgesic activity with the physicochemical properties indicated that conjugation (and planarity) of the amide group with the aromatic ring is essential for activity and that ease of oxidation may also be an important factor.
- Barnard,Storr,O'Neill,Park
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p. 736 - 744
(2007/10/02)
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- A new approach to the chemical synthesis of the trisaccharide, and the terminal di- and mono-saccharide units of the major, serologically active glycoplipid from Mycobacterium leprae
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The key intermediates for the synthesis of p-trifluoroacetamidophenyl O-(3,6-di-O-methyl-β-D-glucopyranosyl)-(1 → 4)-O-(2,3-di-O-methyl-α-L-rhamnopyranosyl)-(1 → 2)-3-O-methyl-α-L-rhamnopyranoside (15), as well as p-trifluoroacetamidophenyl O-(3,6-di-O-me
- Borbas,Liptak
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- Acid-catalyzed amino-migration of O-phenylhydroxylamines
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The mechanism of amino-migration of O-phenylhydroxylamine (1a) was studied. It was found that 1 rearranges to give 2-aminophenol (50%) and 4-aminophenol (7%) in trifluoroacetic acid (TFA). The predominance of the ortho rearrangement of 1 clearly distinguishes this process from the Bamberger rearrangement. From cross-coupling experiments employing stable isotopes, it was clarified that the ortho rearrangement proceeds intramolecularly and the para rearrangement involves both intra- and intermolecular processes. Good first-order kinetics were obtained for the rearrangement. The Hammett plot (σ+) with a large negative slope (ρ = -7.8) indicates that initial heterolytic N-O bond cleavage of 1 occurs and generates a positive charge on the oxygen atom with considerable delocalization into the aromatic ring. An ion-molecule pair involving a phenoxenium ion and an ammonia molecule as an intermediate rationalizes all of the results. In this pair, intramolecular combination to the ortho position proceeds preferentially over that to the para position. Formation of catechol and hydroquinone can be explained in terms of nucleophilic attack of TFA on the phenoxenium ion in a solvent-separated pair.
- Haga, Naoki,Endo, Yasuyuki,Kataoka, Ken-Ichiro,Yamaguchi, Kentaro,Shudo, Koichi
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p. 9795 - 9806
(2007/10/02)
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- Antibodies which catalyze hydrolysis of ester bonds
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An analog-ligand having a conformation that substantially corresponds to the conformation of a hydrolytic transition state of an amide or ester reactant ligand is used to produce receptor molecules of predetermined specificity. The receptor molecules include an antibody combining site that binds to a reactant ligand and thereby stabilizes the tetrahedral carbon atom of the amide or ester hydrolysis transition state of that reactant ligand to catalytically hydrolyze the reactant ligand at a predetermined site.
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- 2-(Trifluoroacetyloxy)pyridine as a Mild Trifluoroacetylating Reagent of Amines and Alcohols
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A new trifluoroacetylating reagent, 2-(trifluoroacetyloxy)pyridine (TFAP), was prepared by the reaction of 2-pyridinol and trifluoroacetic anhydride.TFAP has been found to be effective in the trifluoroacetylation of aliphatic and aromatic amines and alcohols including phenol under mild conditions.The reaction of p-nitrophenol with TFAP in ether gave the hydrogen-bonded complex between the phenol and 2-pyridone.This reagent has also been shown to be useful for the intramolecular dehydration of aldehyde oximes and amides to give nitriles in high yields.
- Keumi, Takashi,Shimada, Masakazu,Morita, Toshio,Kitajima, Hidehiko
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p. 2252 - 2256
(2007/10/02)
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- N-(ω-cyanoalkyl)aminophenols and use as inhibitors of lipoxygenase activity
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N-(ω-cyanoalkyl)aminophenols of formula STR1 useful as lipoxygenase inhibitors and anti-asthmatic agents, are prepared by acylation of an aminophenol with an ω-haloalkanoyl chloride followed by reduction of the resulting amide then displacement of the halide by cyanide.
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