- Method for the Direct Enantioselective Synthesis of Chiral Primary α-Amino Ketones by Catalytic α-Amination
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A useful catalytic enantioselective approach has been developed for the synthesis of chiral ketamine analogs using Rh(II)-catalyzed amination of triisopropylsilyl enol ethers to form α-amino ketones with O-(4-nitrophenyl)hydroxylamine as nitrogen donor in 81-91% ee.
- Han, Yixin,Corey
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supporting information
p. 283 - 286
(2019/01/10)
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- Rhodium(III)-Catalyzed Cascade Redox-Neutral C–H Functionalization and Aromatization: Synthesis of Unsymmetrical ortho-Biphenols
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An efficient rhodium(III)-catalyzed coupling reaction of N-aryloxyacetamides with 6-diazo-2-cyclohexenones through a cascade redox-neutral C–H functionalization and aromatization has been developed. This novel and scalable transformation provides a straightforward way to construct unsymmetrical ortho-biphenols with broad substrate scope under mild and redox-neutral conditions. The synthetic utility of this approach is demonstrated in the late-stage functionalization of bioactive compounds and the synthesis of an optically active ortho-biphenol. (Figure presented.).
- Hu, Zhiyong,Liu, Guixia
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supporting information
p. 1643 - 1648
(2017/05/22)
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- Visible-Light-Mediated Generation of Nitrogen-Centered Radicals: Metal-Free Hydroimination and Iminohydroxylation Cyclization Reactions
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The formation and use of iminyl radicals in novel and divergent hydroimination and iminohydroxylation cyclization reactions has been accomplished through the design of a new class of reactive O-aryl oximes. Owing to their low reduction potentials, the inexpensive organic dye eosin Y could be used as the photocatalyst of the organocatalytic hydroimination reaction. Furthermore, reaction conditions for a unique iminohydroxylation were identified; visible-light-mediated electron transfer from novel electron donor-acceptor complexes of the oximes and Et3N was proposed as a key step of this process.
- Davies, Jacob,Booth, Samuel G.,Essafi, Stephanie,Dryfe, Robert A. W.,Leonori, Daniele
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p. 14017 - 14021
(2016/01/25)
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- Rhodium(III)-catalyzed C-H olefination for the Synthesis of ortho-alkenyl phenols using an oxidizing directing group
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By using an oxidizing directing group, a mild, efficient Rh(III) catalyzed C-H olefination reaction between N-phenoxyacetamides and alkenes was developed. This reaction provided a straightforward way for the synthesis of ortho-alkenyl phenols, and the directing group is traceless in the product.
- Shen, Yangyang,Liu, Guixia,Zhou, Zhi,Lu, Xiyan
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p. 3366 - 3369
(2013/07/26)
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- PROCESS FOR PREPARING BENZOFURAN DERIVATIVES SUBSTITUTED AT POSITION 5
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The disclosure relates to a process for preparing benzofuran derivatives of general formula I: in which R, R1, and R2 are as defined in the disclosure; by coupling the hydroxylamine with a diketone of general formula III: in order to form an oxime that is then cyclized by heating in order to form the desired compound.
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- Chemoselective amide formation using O-(4-nitrophenyl)hydroxylamines and pyruvic acid derivatives
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A series of O-(4-nitrophenyl)hydroxylamines were synthesized from their respective oximes using a pulsed addition of excess NaBH3CN at pH 3 in 65a-75% yield. Steric hindrance near the oxime functional group played a key role in both the ease by which the oxime could be reduced and the subsequent reactivity of the respective hydroxylamine. Reaction of the respective hydroxylamines with pyruvic acid derivatives generated the desired amides in good yields. A comparison of phenethylamine systems bearing different leaving groups revealed significant differences in the rates of these systems and suggested that the leaving group ability of the Na-OR substituent plays an important role in determining their reactivity with pyruvic acid. Competition experiments (in 68% DMSO/phosphate buffered saline) using 1 equiv of N-phenethyl-O-(4-nitrophenyl)hydroxylamine and 2 equiv of pyruvic acid in the presence of other nucleophiles such as glycine, cysteine, phenol, hexanoic acid, and lysine demonstrated that significant chemoselectivity is present in this reaction. The results suggest that this chemoselective reaction can occur in the presence of excess α-amino acids, phenols, acids, thiols, and amines.
- Kumar, Sonali,Sharma, Rashi,Garcia, Megan,Kamel, Joseph,McCarthy, Caroline,Muth, Aaron,Phanstiel, Otto
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p. 10835 - 10845
(2013/02/23)
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- NEW PROCESS FOR PREPARING DIKETONES AND MEDICAMENTS
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There is provided a process for the preparation of a compound of formula (III), wherein X and Y are as described in the description. Such compounds may, for example, be useful intermediates in the synthesis of drugs such as Dronedarone. There is also provided a process for the preparation of a compound of formula (I).
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Page/Page column 45
(2010/04/27)
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- NEW PROCESS FOR PREPARING HYDROXYLAMINES AND MEDICAMENTS
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There is provided a process for the preparation of a compound of formula (II), wherein R1, R2, R3 and R4 are as described in the description. Such compounds may, for example, be useful intermediates in the synthesis of drugs such as Dronedarone.
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Page/Page column 47
(2010/11/03)
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- PROCESS FOR PREPARING BENZOFURANS
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There is provided a process for the preparation of a compound of formula (I), wherein R1, R2, R3, R4, X and Y are as described in the description. Such compounds may, for example, be useful intermediates in the synthesis of drugs such as Dronedarone.
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Page/Page column 38
(2009/05/29)
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- Aldehyde detection by chromogenic/fluorogenic oxime bond fragmentation
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Amination of 4-nitrophenol, umbelliferone and 4-methylumbelliferone gave the corresponding oxyamines 1-3. These oxyamines react with aldehydes and ketones to form oximes. In the case of aliphatic aldehydes and electron-poor aromatic aldehydes, the oximes undergo base-catalyzed fragmentation in aqueous buffer in the presence of bovine serum albumin to give the parent phenols, which is the acyclic analog of Kemp's elimination reaction of 5-nitrobenzisoxazole 28. The process can be used as a spectrophotometric assay for formaldehyde under aqueous neutral conditions.
- Salahuddin, Syed,Renaudet, Olivier,Raymond, Jean-Louis
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p. 1471 - 1475
(2007/10/03)
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- Electrophilic N-amination of two quinazoline-2,4-diones using substituted (Nitrophenyl)hydroxylamines
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The preparation of a few (nitrophenyl)hydroxylamines and reaction with two quinazoline-2,4-diones is described. The electrophilic aminating agents were assessed in terms of yield for the N-amination of two quinazoline-2,4-diones and safety considerations for rapid scale-up. For the amination of the described system, the best yield and the highest onset temperature were found in the same aminating agent, specifically, (4-nitrophenyl)hydroxylamine.
- Boyles, David C.,Curran, Timothy T.,Parlett IV, Roger V.,Davis, Mark,Mauro, Frank
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p. 230 - 233
(2013/09/06)
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- Imine exchange in O-aryl and O-alkyl oximes as a base reaction for aqueous 'dynamic' combinatorial libraries. A kinetic and thermodynamic study
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Kinetics and mechanisms of the imine exchange reactions of O-alkyl and O-aryl oximes with O-alkyl-and O-aryloxyamines, respectively, were studied by 1H NMR spectroscopy in aqueous solutions. The reaction between benzaldehyde O-methyloxime and O-ethylhydroxylamine at 60 °C is first order in both oxime and the alkoxylamine (the second-order rate constant k2 = 0.86 ± 0.081 mol-1 min-1 at pD 2.9). the reaction being subject to acidic catalysis. A similar imine transfer was studied in the reaction of 1,3-diaminooxyprog with bifunctional oximes. Testing of various additives as potential catalysts for the reaction revealed imidazole as a moderately effective catalyst. The exchange in O-aryl oximes was studied in the interaction between 3-pyridinealdehyde O-pnenyloxime and O-(p-nitrophenyl)hydroxylamine. The reaction is first order in the oxime, but its is independent on the aryloxyamine concentration and pD. The proposed mechanism involves a rate-limiting hydration of the oxime molecule. Mechanisms of the exchange reactions are discussed in relation to their possible use to generate diverse pools of compounds for the recently proposed 'dynamic' combinatorial chemistry approach Copyright
- Polyakov, Vladimir A.,Nelen, Marina I.,Nazarpack-Kandlousy, Noureddin,Ryabov, Alexander D.,Eliseev, Alexey V.
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p. 357 - 363
(2007/10/03)
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- Synthesis of Phenoxyamines
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Treatment of phenols with 2,4-dinitrophenoxyamine leads to the synthesis of phenoxyamines through an amine exchange reaction.Yields for this reaction are sensitive to the pKa of the phenol in a manner explainable in terms of a competing bimolecular decomposition reaction involving the 2,4-dinitrophenoxyamines.By use of an appropriately sustituted phenol, this phenomenon can be exploited to give high yields of phenoxyamines having oxygenated substitution patterns that were unattainable by previous methods.
- Castellino, Angelo J.,Rapoport, Henry
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p. 1348 - 1352
(2007/10/02)
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- Acid-Catalyzed Solvolysis of N-Sulfonyl- and N-Acyl-O-arylhydroxylamines. Phenoxenium Ions
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The acid-catalyzed reaction of N-acyl- and N-sulfonyl-O-arylhydroxylamines with benzene proceeded quite smoothly to give 2- and 4-hydroxybiphenyls.The results of product analysis, the orientation of the reaction, and the effects of substituents on the nitrogen atom and on the phenyl ring suggested a mechanism that involves a phenoxenium ion.The phenoxenium ion was trapped by benzene and other various nucleophiles.
- Endo, Yasuyuki,Shudo, Koichi,Okamoto, Toshihiko
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p. 6393 - 6397
(2007/10/02)
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- Aryloxenium Ions. Generation from N-(Aryloxy)pyridinium Tetrafluoroborates and Reaction with Anisole and Benzonitrile
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N-(Aryloxy)pyridinium tetrafluoroborates (4) decompose thermally at 180-200 deg C in anisole and benzonitrile to form products of intermolecular C-O-C and C-C bond formation.With anisole, diphenyl ethers (5) and hydroxybiphenyls (6) are formed; with benzonitrile, the main product is benzoxazole (14).A homolytic process was ruled out by showing that none of these products were formed when perbenzoyl p-nitrophenyl carbonate (18) was decomposed in these solvents.The main products in this case were those of homolytic phenylation (and benzoyloxylation with anisole).A concerted SN2-type heterolytic process was ruled out by showing that the nature of the substituent in the pyridine ring had no effect on the isomer ratios of 5 and 6 in the thermolysis of 4 (X = p-NO2) in anisole.The results are explained in terms of a unimolecular heterolysis of 4 to give the pyridine and aryloxenium ion 2 which now attacks solvent molecules.When an electron-withdrawing substituent is present in 2, more C-O-C than C-C products are formed in anisole.When it is absent only products of C-C bond formation are found.PhO+ is apparently electrophilic enough to attack anisole and give the four possible hydroxymethoxybiphenyls (10-13).
- Abramovitch, Rudolph A.,Alvernhe, Gerard,Bartnik, Romuald,Dassanayake, Nissanke L.,Inbasekaran, Mutiah N.,Kato, Shiego
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p. 4558 - 4565
(2007/10/02)
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