- An Effective Method for the Synthesis of 1,3-Dihydro-2H-indazoles via N-N Bond Formation
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The [4+1] cycloaddition reaction of bifunctional amino reagents has been achieved with in situ formed aza-ortho-quinone methides. Specifically, N-(tosyloxy)carbamates were used as an N1 synthon and bifunctional amino reagents for this transformation, which provides a metal-free, catalyst-free, and oxidant-free strategy to form nitrogen-nitrogen bonds. (Figure presented.).
- Zhang, Xiaoke,Pan, Yang,Liang, Peng,Ma, Xiaofeng,Jiao, Wei,Shao, Huawu
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supporting information
p. 5552 - 5557
(2019/11/22)
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- Synthesis of indoles from aroyloxycarbamates with alkynes: Via decarboxylation/cyclization
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An efficient Pd-catalyzed decarboxylation/cyclization of aroyloxycarbamates to realize substituted indoles has been disclosed. Terminal alkynes as the coupling partners lead to site specific 2-substituted indoles through two pathways, while internal alkynes with aroyloxycarbamates can be transformed to 2,3-disubstituted indoles directly. This protocol is further demonstrated by the efficient synthesis of indoles as well as the success of employing inexpensive aryl acids as starting materials to construct C-N bonds by releasing CO2.
- Ma, Nuannuan,Li, Peihe,Wang, Zheng,Dai, Qipu,Hu, Changwen
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supporting information
p. 2421 - 2426
(2018/04/12)
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- Synthesis of N-Oxyureas by Substitution and Cope-Type Hydroamination Reactions Using O-Isocyanate Precursors
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Oxy-carbamate O-isocyanate precursors facilitate access to synthetically valuable N-oxyureas via substitution with amines. This work exploits the reactivity of suitable O-isocyanate precursors, identified by a thorough study highlighting the different reactivity of isocyanate masking groups. This led to bench-stable O-isocyanate precursors, offering improved versatility in the synthesis of N-oxyureas, and demonstrates the controlled reactivity of masked O-isocyanates. Suitable precursors also enabled the first example of Cope-type hydroamination of unsaturated hydroxyureas.
- Allen, Meredith A.,Ivanovich, Ryan A.,Polat, Dilan E.,Beauchemin, André M.
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supporting information
p. 6574 - 6577
(2017/12/26)
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- Regioselective Synthesis of 2-Vinylanilines Using O-aroyloxycarba-mates by Sequential Decarboxylation/Amination/Heck Reaction
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A new sequential approach for 2-vinylanilines utilizing aryl carboxylic acids as stable, inexpensive and widely available arylating reagents is described. Employing a Pd-POVs catalyst system, this protocol is not only overcoming the restriction barrier of decarboxylative coupling to ortho-substituted substrates, but also provides site-special to create new C(sp2)-N and C(sp2)-C(sp2) bonds. Mechanistic experiments suggest the cleavage of C(sp2)-COOH gives priority to C(sp2)-X bond in this reaction.
- Li, Peihe,Ma, Nuannuan,Li, Jikun,Wang, Zheng,Dai, Qipu,Hu, Changwen
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p. 8251 - 8257
(2017/08/14)
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- Palladium-Catalyzed Decarboxylative Synthesis of Arylamines
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A novel approach has been developed for the synthesis of arylamines via the palladium-catalyzed intramolecular decarboxylative coupling (IDC) of aroyloxycarbamates, obtained in situ by reacting aryl carboxylic acids with hydroxycarbamates. The reaction offers facile access to structurally diverse arylamines with the site-specific formation of the C(sp2)-N bond under mild conditions.
- Dai, Qipu,Li, Peihe,Ma, Nuannuan,Hu, Changwen
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supporting information
p. 5560 - 5563
(2016/11/17)
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- Iron(II)-catalyzed intermolecular amino-oxygenation of olefins through the N - O bond cleavage of functionalized hydroxylamines
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An iron-catalyzed diastereoselective intermolecular olefin amino-oxygenation reaction is reported, which proceeds via an iron-nitrenoid generated by the N - O bond cleavage of a functionalized hydroxylamine. In this reaction, a bench-stable hydroxylamine derivative is used as the amination reagent and oxidant. This method tolerates a range of synthetically valuable substrates that have been all incompatible with existing amino-oxygenation methods. It can also provide amino alcohol derivatives with regio- and stereochemical arrays complementary to known amino-oxygenation methods.
- Lu, Deng-Fu,Zhu, Cheng-Liang,Jia, Zhen-Xin,Xu, Hao
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supporting information
p. 13186 - 13189
(2015/03/30)
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- Alkyl 4-chlorobenzoyloxycarbamates as highly effective nitrogen source reagents for the base-free, intermolecular aminohydroxylation reaction
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Ethyl-(7), benzyl-(8), tert-butyl-(9), and fluorenylmethyl-4- chlorobenzoyloxycarbamates (10) have been prepared as storable and easy-to-prepare nitrogen sources for use in the intermolecular Sharpless aminohydroxylation reaction and its asymmetric variant. These reagents were found to be effective under base-free reaction conditions. The scope and limitations of these methods have been explored using a variety of alkenes, among which, trans-cinnamates, in particular, proved to be good substrates.
- Harris, Lawrence,Mee, Simon P. H.,Furneaux, Richard H.,Gainsford, Graeme J.,Luxenburger, Andreas
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experimental part
p. 358 - 372
(2011/04/17)
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- IMPROVED AMINOHYDROXYLATION OF ALKENES
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The invention relates to a process for the aminohydroxylation of alkenes using N-oxycarbamate reagents, e.g. N-acyloxycarbamate, N-alkyloxycarbonyloxycarbamate and N-aralkoxycarbonyloxycarbamate reagents. The invention particularly relates to an intermolecular aminohydroxylation reaction that can be carried out in the absence of added base. The invention also relates to novel N-oxycarbamate reagents that are stable crystalline materials. The process of the invention is useful in the synthesis of compounds having a vicinal amino alcohol moiety, such as biologically active compounds.
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Page/Page column 40
(2012/01/06)
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- IMPROVED PROCESS FOR THE PREPARATION OF (±)-1-(1-BENZO[B]THIEN-2-YLETHYL)-1-HYDROXYUREA
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The present invention relates to an improved process for the preparation of (±)-1-(I -Benzo[b]thien-2-ylethyl)-1-hydroxyurea compound of formula 1.
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Page/Page column 19
(2011/04/24)
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- Synthesis and in vitro cytotoxic activity of N-2-(2-furyl)-2- (chlorobenzyloxyimino) ethyl ciprofloxacin derivatives
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Quinolone are a class of potent broad-spectrum antibacterial drugs that target the bacterial type II DNA topoisomerases (DNA gyrase) and topoisomerase IV. In the present study, the synthesis and evaluation of cytotoxicity activity of a new series of N-pipearzinyl quinolones containing N-2-(furyl-2-yl)-2- (chlorobenzyloxyimino) ethyl moiety (6a-c) have been studied. Preliminary screening showed that one of the new compounds, namely 7-(4-(2-(3- chlorobenzyloxyimino)-2-(furan-2-yl) ethyl) piperazin-1-yl)-1-cyclopropyl-6- fluoro-4-oxo-1, 4-dihydroquinoline-3-carboxylic acid (6b) showed significant cytotoxic activity against human breast tumor cell lines.
- Alipour, Eskandar,Mohammadhosseini, Negar,Panah, Fatemeh,Ardestani, Sussan K.,Safavi, Maliheh,Shafiee, Abbas,Foroumadi, Alireza
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scheme or table
p. 1226 - 1231
(2012/06/30)
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- Pd-catalyzed intermolecular ortho-C-H amidation of anilides by N-nosyloxycarbamate
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A palladium-catalyzed ortho-C-H amidation of anilides by N-nosyloxycarbamates was developed for the synthesis of 2-aminoanilines. This reaction can be carried out under relatively mild conditions and exhibits excellent regioselectivity and functional group tolerance. The amidation reaction is probably initiated by rate-limiting C-H cyclopalladation (k H/kD = 3.7) to form an arylpalladium complex, followed by nitrene functionalization.
- Ng, Ka-Ho,Chan, Albert S. C.,Yu, Wing-Yiu
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supporting information; experimental part
p. 12862 - 12864
(2010/11/03)
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- Synthetic techniques and intermediates for polyhydroxy, dienyl lactone derivatives
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Synthetic methods for lactone-containing compounds such as the discodermolides are provided, as are compounds which mimic the chemical and/or biological activity thereof, and methods and intermediates useful in their preparation.
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- N-nitroso-N,O-dialkylhydroxylamines: Preparation, structure, and mechanism of the hydronium ion catalysed solvolytic nitrous oxide extrusion reaction
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Eleven N-nitroso-N,O-dialkylhydroxylamines, RN(NO)OR′, have been prepared and the mechanisms of their hydronium ion catalysed solvolyses in aqueous solution which liberate nitrous oxide have been investigated. All reactions are first-order in substrate and first-order in hydronium ion, and the second-order rate constants at 25°C vary over a range of less than 140 in spite of considerable variation in substrate structure (R ranges from methyl to 4-methoxybenzyl to 2-adamantyl, for example) and changes in solvent composition (water with up to 50% methanol or 66% acetonitrile). Enthalpies and entropies of activation are qualitatively similar throughout the range (ΔH?= 72-93 kJ mol-1 and ΔS? = -19 to -57 J K-1 mol-1) which, with the product analyses, are accommodated by a mechanism involving pre-equilibrium protonation of the substrates followed by rate-limiting dissociation to give RN2O+ and HOR′. The oxodiazonium ion intermediate, RN2O+, then dissociates further to give the carbenium ion intermediate, R+, or suffers direct nucleophilic displacement of N2O by solvent (the external nucleophile) or by R′OH (the internal nucleophile liberated in the initial fragmentation). The carbenium ion, R+ (if formed), suffers nucleophilic capture either by solvent or by R′OH. When acetonitrile is the co-solvent (rather than methanol) for the N-(2-adamantyl) substrate 3g, the product of the Ritter reaction, 2-acetamidoadamantane, is detected. These nitrous oxide liberating reactions are compared with the nitric oxide liberating reactions of related N-nitrosohydroxylamines, and the origin of the difference between them is identified. The N(1)-nitroso group in the N,O-dibenzyl compound 3c is shown by X-ray crystallography to be essentially coplanar with the C and O atoms also bonded to N(1).
- Bhat, J. Ishwara,Clegg, William,Maskill, Howard,Elsegood, Mark R.J.,Menneer, Iain D.,Miatt, Peter C.
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p. 1435 - 1446
(2007/10/03)
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- Synthetic techniques and intermediates for polyhydroxy, dienyl lactones and mimics thereof
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Synthetic methods for lactone-containing compounds such as the discodermolides are provided, as are compounds which mimic the chemical and/or biological activity thereof, and methods and intermediates useful in their preparation.
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- Carbamates
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Carbamate compounds of the formula: in which CO.X.CO is the diacyl radical of a polybasic carboxylic acid, and R1 is an optionally substituted hydrocarbyl radical; more particularly, X is a member of the group consisting of a direct link, C1 to C4 alkylene groups, C2 to C3 alkenylene, o-phenylene and p-phenylene and R1 is a member of the group consisting of C1 to C18 alkyl, phenyl, chlorophenyl, nitrophenyl, cyclohexyl and benzyl. These carbamates are useful as cross-linking agents in natural rubbers or synthetic rubbers based on isoprene or butadiene polymers.
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