- Carbamates: A Directing Group for Selective C-H Amidation and Alkylation under Cp*Co(III) Catalysis
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The selective reactivity of carbamate and thiocarbamate toward alkylation and amidation is reported under stable, high-valent, cost-effective cobalt(III) catalysis. This method reveals the wide possibility of designing a different branch of synthetically
- Bera, Sourav Sekhar,Maji, Modhu Sudan
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supporting information
p. 2615 - 2620
(2020/04/08)
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- Iron(II)/Persulfate Mediated Newman-Kwart Rearrangement
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Herein, we report that iron(II)/ammonium persulfate in aqueous acetonitrile mediates the Newman-Kwart rearrangement of O-aryl carbamothioates. Electron-rich substrates react rapidly under moderate heating to afford the rearranged products in excellent yie
- Gendron, Thibault,Pereira, Raul,Abdi, Hafsa Y.,Witney, Timothy H.,?rstad, Erik
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supporting information
p. 274 - 278
(2020/01/02)
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- Electrochemically Catalyzed Newman-Kwart Rearrangement: Mechanism, Structure-Reactivity Relationship, and Parallels to Photoredox Catalysis
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The facilitation of redox-neutral reactions by electrochemical injection of holes and electrons, also known as "electrochemical catalysis", is a little explored approach that has the potential to expand the scope of electrosynthesis immensely. To systematically improve existing protocols and to pave the way toward new developments, a better understanding of the underlying principles is crucial. In this context, we have studied the Newman-Kwart rearrangement of O-arylthiocarbamates to the corresponding S-aryl derivatives, the key step in the synthesis of thiophenols from the corresponding phenols. This transformation is a particularly useful example because the conventional method requires temperatures up to 300 °C, whereas electrochemical catalysis facilitates the reaction at room temperature. A combined experimental-quantum chemical approach revealed several reaction channels and rendered an explanation for the relationship between the structure and reactivity. Furthermore, it is shown how rapid cyclic voltammetry measurements can serve as a tool to predict the feasibility for specific substrates. The study also revealed distinct parallels to photoredox-catalyzed reactions, in which back-electron transfer and chain propagation are competing pathways.
- Roesel, Arend F.,Ugandi, Mihkel,Huyen, Nguyen Thi Thu,Májek, Michal,Broese, Timo,Roemelt, Michael,Francke, Robert
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p. 8029 - 8044
(2020/07/25)
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- An Electrocatalytic Newman-Kwart-type Rearrangement
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An electrochemical approach toward rearrangement of O-aryl thiocarbamates to the corresponding S-aryl thiocarbamates is presented. The protocol requires only catalytic amounts of electric charge and allows for operation at room temperature. The electrolys
- Broese, Timo,Roesel, Arend F.,Prudlik, Adrian,Francke, Robert
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supporting information
p. 7483 - 7487
(2019/01/03)
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- Microwave-mediated Newman-Kwart rearrangement in water
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For the first time the unimolecular Newman-Kwart rearrangement is performed in pure water. The elevated temperatures required for the 1,3-aryl shift are easily accomplished by microwave irradiation. Differently functionalized substrates underline the expe
- Hoffmann, Ina,Schatz, Jürgen
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p. 80692 - 80699
(2016/09/09)
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- Ambient-Temperature Newman-Kwart Rearrangement Mediated by Organic Photoredox Catalysis
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The Newman-Kwart rearrangement is perhaps the quintessential method for the synthesis of thiophenols from the corresponding phenol. However, the high thermal conditions required for the rearrangement of the requisite O-aryl carbamothioates often leads to decomposition. Herein, we present a general strategy for catalysis of O-aryl carbamothioates to S-aryl carbamothioates using catalytic quantities of a commercially available organic single-electron photooxidant. Importantly, this reaction is facilitated at ambient temperatures.
- Perkowski, Andrew J.,Cruz, Cole L.,Nicewicz, David A.
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supporting information
p. 15684 - 15687
(2016/01/09)
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- Palladium-catalyzed intramolecular oxidative C-H sulfuration of aryl thiocarbamates
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A palladium-catalyzed intramolecular C-H bond sulfuration reaction of aryl thiocarbamates has been developed. This strategy provides a new route to benzo[d][1,3]oxathiol-2-ones with tolerance of a wide range of substituents. Mechanistic studies suggested
- Zhao, Yingwei,Xie, Yinjun,Xia, Chungu,Huang, Hanmin
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supporting information
p. 2471 - 2476
(2014/09/17)
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- Ago-allosteric modulators of human glucagon-like peptide 2 receptor
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Glucagon-like peptide 2 (GLP-2) is an intestinotropic peptide that binds to GLP-2 receptor (GLP-2R), a class-B G protein-coupled receptor (GPCR). Few synthetic agonists have been reported so far for class-B GPCRs. Here, we report the first scaffold compounds of ago-allosteric modulators for human GLP-2R, derived from methyl 2-{[(2Z)-2-(2,5-dichlorothiophen-3-yl)-2-(hydroxyimino) ethyl]sulfanyl}benzoate (compound 1).
- Yamazaki, Kazuto,Terauchi, Hiroki,Iida, Daisuke,Fukumoto, Hironori,Suzuki, Shuichi,Kagaya, Takaki,Aoki, Mika,Koyama, Koichiro,Seiki, Takashi,Takase, Kazuma,Watanabe, Misako,Arai, Tohru,Tsukahara, Kappei,Nagakawa, Junichi
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p. 6126 - 6135
(2012/10/30)
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- A high temperature investigation using microwave synthesis for electronically and sterically disfavoured substrates of the Newman-Kwart rearrangement
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Electronically deactivated and/or sterically hindered substrates undergo the Newman-Kwart rearrangement (NKR) at around 300 °C, beyond the range of most convenient and safe, small-scale laboratory equipment. We report here the convenient conversions of several difficult substrates using modern microwave technology, which has proven ideal for investigating this high temperature reaction in all but the?most refractory of cases. In addition, several previously reported difficult examples were re-investigated, and found not to require high temperatures under these conditions, for various reasons which are elaborated upon.
- Moseley, Jonathan D.,Lenden, Philip
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p. 4120 - 4125
(2008/01/03)
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- The Newman-Kwart rearrangement re-evaluated by microwave synthesis
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The Newman-Kwart rearrangement (NKR) has been re-evaluated by microwave heating. Microwave technology has proven to be ideal for investigating this high temperature rearrangement and facilitated the confirmation of many aspects of this valuable reaction.
- Moseley, Jonathan D.,Sankey, Rosalind F.,Tang, Olivier N.,Gilday, John P.
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p. 4685 - 4689
(2007/10/03)
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- Organosulfur compounds as pre-exposure therapy for threat agents.
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A series of symmetric (Ar-S-S-Ar) and unsymmetric (Ar-S-S-CH2CH2NH3+Cl-) disulfides have been prepared and evaluated as potential cyanoprotective agents. Target compounds have been prepared by known methods and/or methods developed by us specifically for this program, e.g. reaction of a thiol with 2,2'-dithiobis(benzothiazole) (BT-S-S-BT) followed by reaction with a second thiol. Both 4-methoxyphenyl disulfide and 2-aminoethyl-4-methoxyphenyl disulfide hydrochloride are cyanoprotective against 2-LD50 of injected cyanide. Evaluation of both symmetric and unsymmetric related disulfides indicates that structural requirements for cyanoprotective activity are stringent and strongly suggest that protection is enzyme mediated. In addition to cyanoprotective action, initial results suggest that unsymmetric disulfides may evolve into effective antimustard agents.
- Ternay Jr.,Brzezinska,Sorokin,Cook,Lyaschenko
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- Rapid and Selective Reduction of Functionalized Aromatic Disulfides with Lithium Tri-tert-butoxyaluminohydride. A Remarkable Steric and Electronic Control. Comparison of Various Hydride Reagents
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Lithium tri-tert-butoxyaluminohydride (LTBA), an exceptionally mild reducing agent in organic synthesis, reduces functionalized aromatic disulfides to the corresponding thiols in quantitative yield.The reaction is rapid (for example, o-tolyl disulfide is reduced to completion in 60 min at 25 deg C) and can tolerate a wide variety of functional groups, such as halogen, nitro, carboxylic acid, and their derivatives.The presence of electron-withdrawing substituents dramatically enhances the rate of reduction (p-chlorophenyl disulfide is quantitatively reduced in 30 s) and electron-releasing substituents diminishes the rate of cleavage.The reaction is sensitive to steric effects (2,4-di-tert-pentylphenyl disulfide underwent 25percent reduction in 24 h).However, such hindered disulfides can be rapidly and quantitatively reduced in refluxing THF.The reaction of LTBA with alkyl disulfides is extremely sluggish.The reaction provides a useful and simple means for the facile and selective reduction of aromatic disulfides where this is required in synthetic operations.
- Krishnamurthy, S.,Aimino, D.
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p. 4458 - 4462
(2007/10/02)
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