- Functionalization of α-C(sp3)?H Bonds in Amides Using Radical Translocating Arylating Groups
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α-C?H arylation of N-alkylamides using 2-iodoarylsulfonyl radical translocating arylating (RTA) groups is reported. The method allows the construction of α-quaternary carbon centers in amides. Various mono- and disubstituted RTA-groups are applied to the arylation of primary, secondary, and tertiary α-C(sp3)?H-bonds. These radical transformations proceed in good to excellent yields and the cascades comprise a 1,6-hydrogen atom transfer, followed by a 1,4-aryl migration with subsequent SO2 extrusion.
- Radhoff, Niklas,Studer, Armido
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supporting information
p. 3561 - 3565
(2021/01/04)
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- Ni-Catalyzed Regiodivergent and Stereoselective Hydroalkylation of Acyclic Branched Dienes with Unstabilized C(sp3) Nucleophiles
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Two complementary regiodivergent [(P,N)Ni]-catalyzed hydroalkylations of branched dienes are reported. When amides are employed as unstabilized C(sp3) nucleophiles, a highly regioselective 1,4-addition process is favored. The addition products are obtained in high yield and with excellent stereocontrol of the internal olefin. With use of a chiral ligand and imides as carbon nucleophiles, a 3,4-addition protocol was developed, enabling construction of two contiguous tertiary stereocenters in a single step with moderate to high levels of diastereocontrol and excellent enantiocontrol. Both methods operate under mild reaction conditions, display a broad scope, and show excellent functional group tolerance. The synthetic potential of the 3,4-hydroalkylation reaction was established via a series of postcatalytic modifications.
- Shao, Wen,Besnard, Céline,Guénée, Laure,Mazet, Clément
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supporting information
p. 16486 - 16492
(2020/10/26)
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- Rh(III)-Catalyzed Distal C-H Alkenylation of Weakly Coordinating Acetamides Via Desilylation Pathway
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Rh(III)-Catalyzed distal ortho-C?H alkenylation of arylacetamides have been reported employing acetamide, a weak coordinating group, as a directing group. This challenging C?H alkenylation of arylacetamides has been achieved by using arylalkynyl silanes as a surrogate for terminal alkynes under redox neutral process through desilylation pathway. The control experiments suggest that the in situ generatedRh-species is likely to be Lewis acidic, which is playing a vital role in the desilylation step. (Figure presented.).
- Ramesh, Vinay Bapu,Muniraj, Nachimuthu,Prabhu, Kandikere Ramaiah
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supporting information
p. 3683 - 3688
(2019/07/12)
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- Solvent-Free N-Alkylation of Amides with Alcohols Catalyzed by Nickel on Silica–Alumina
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The N-alkylation of phenylacetamide with benzyl alcohol has been studied using Ni/SiO2–Al2O3. In the optimized conditions, the desired product was isolated in an excellent 98 % yield. The reaction could advantageously be performed in neat conditions, with a slight excess of amide and a catalytic amount of base. These conditions were tested on a large range of amides and alcohols, affording 24 compounds in 13 to 99 % isolated yields.
- Charvieux, Aubin,Le Moigne, Louis,Borrego, Lorenzo G.,Duguet, Nicolas,Métay, Estelle
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supporting information
p. 6842 - 6846
(2019/11/11)
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- Synthesis of Unsymmetrical Diaryl Acetamides, Benzofurans, Benzophenones, and Xanthenes by Transition-Metal-Free Oxidative Cross-Coupling of sp3 and sp2 C-H Bonds
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A chemo- and regioselective intermolecular sp3 C-H and sp2 C-H coupling reaction for C-C bond formation is described to access unsymmetrical diaryl acetamides under TM-free conditions from sec- and tert-arylacetamides and nitroarenes using tert-butoxide base in DMSO at room temperature. The coupling partners with sensitive functionalities such as chloro, bromo, hydroxy, and cyano were also amenable to the developed reaction. Synthesized α-(2/4-nitroaryl) phenylacetamides have been transformed into biologically important benzofurans, xanthenes, diaryl indoles, and unsymmetrical benzophenones by novel routes without applying a transition metal. Overall, an economical, yet efficient, strategy has been devised to access unsymmetrical diarylacetamides with the possibility of their further elaboration into a variety of biologically important heterocycles. Mechanistic understanding suggests that the reaction proceeds by a nucleophilic addition of a phenylacetamide carbanion, which is generated in the presence of tert-butoxide base, to the para or ortho (if para is substituted) position of nitrobenzene. The formed α-(4-nitrocyclohexa-2,4-dien-1-yl) phenylacetamide anion intermediate oxidized by a basic solution of DMSO or atmospheric oxygen led to the desired sp3 C-H and sp2 C-H coupled α-(2/4-nitroaryl) phenylacetamides.
- Rathore, Vandana,Sattar, Moh.,Kumar, Raushan,Kumar, Sangit
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p. 9206 - 9218
(2016/10/14)
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- Nickel-Catalyzed Reductive Addition of Aryl/Benzyl Halides and Pseudohalides to Carbodiimides for the Synthesis of Amides
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A Nickel-catalyzed reductive process is described for the direct amidation of benzyl and aryl halides using carbodiimides as the amidating agent. Moreover, aryl and benzyl C–O electrophiles such as triflate, acetate, tosylate, trityl ether, and pivalate were converted into amides using this method. The in-situ-generated Ni0acts as a catalyst for the reaction at room temperature for benzylic substrates, and 70 °C for aryl electrophiles. This new nickel-catalyzed reductive coupling protocol provides a general and operationally simple method for the synthesis of diverse amides using carbodiimides. Amides bearing bulky substituents can be synthesized by this strategy in high yield, which demonstrates its effectiveness in amide synthesis.
- Panahi, Farhad,Jamedi, Fereshteh,Iranpoor, Nasser
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p. 780 - 788
(2017/01/18)
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- Dihydropyrancarboxamides related to zanamivir: A new series of inhibitors of influenza virus sialidases. 1. Discovery, synthesis, biological activity, and structure-activity relationships of 4-guanidino- and 4-amino-4h-pyran-6-carboxamides
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4-Amino- and 4-guanidino-4ff-pyran-6-carboxamides 4 and 5 related to zanamivir (GG167) are a new class of inhibitors of influenza virus sialidases. Structure-activity studies reveal that, in general, secondary amides are weak inhibitors of both influenza
- Smith, Paul W.,Sollis, Steven L.,Howes, Peter D.,Cherry, Peter C.,Starkey, Lan D.,Cobley, Kevin N.,Weston, Helen,Scicinski, Jan,Merritt, Andrew,Whittington, Andrew,Wyatt, Paul,Taylor, Neil,Green, Darren,Bethell, Richard,Madar, Safia,Fenton, Robert J.,Morley, Peter J.,Pateman, Tony,Beresford, Alan
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p. 787 - 797
(2007/10/03)
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- Flash photolytic generation of primary, secondary, and tertiary ynamines in aqueous solution and study of their carbon-protonation reactions in that medium
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A group of nine phenylynamines (PhC≡CNH2, PhC≡CNHCH(CH3)2, PhC≡CNHC6H11, PhC≡CNHC6H5, PhC≡CNHC6F5, PhC≡CN(CH2)5, PhC≡CN(CH2CH2)2O, PhC≡CN(CH2CH2CN)2, and PhC≡CN(CH3)C6F5) were generated in aqueous solution by flash photolytic decarbonylation of the corresponding phenylaminocyclopropenones, and the kinetics of their facile decay in that medium were studied. This decay is catalyzed by acids for all ynamines-primary, secondary, and tertiary-and also by bases for primary and secondary ynamines. Solvent isotope effects and the form of acid-base catalysis show that the acid-catalyzed path involves formation of keteniminium ions by rate-determining proton transfer to the β-carbon atoms of the ynamines. The ions generated from primary and secondary ynamines then lose nitrogen-bound protons to give ketenimines, and the ketenimines obtained from secondary ynamines are hydrated to phenylacetamides, whereas that from the primary ynamine tautomerizes to phenylacetonitrile. Keteniminium ions formed from tertiary ynamines have no nitrogen-bound protons that can be lost, and they are therefore captured by water instead, and the amide enols thus produced then ketonize to phenylacetamides. The base-catalyzed decay of primary and secondary ynamines also generates ketenimines, but protonation on the β-carbon is now preceeded by proton removal from nitrogen. Rate constants for β-carbon protonation of PhC≡CNHCH(CH3)2 and PhC≡CN(CH2)5 by a series of carboxylic acids give linear Bronsted relations with exponents α = 0.29 and 0.28, respectively, whereas inclusion of literature data for protonation of PhC≡CN-(CH2)5 by a group of weaker acids gives a curved Bronsted relation whose exponent varies from 0.25 to 0.97. Application of Marcus rate theory to this curved Bronsted relation produces the intrinsic barrier ΔG((+))(o) = 3.26 ± 0.19 kcal mol-1 and the work term w(r) = 8.11 ± 0.15 kcal mol-1.
- Chiang,Grant,Kresge,Paine
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p. 4366 - 4372
(2007/10/03)
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- A novel and versatile route to mixed p-toluenesulphonic carboxylic anhydrides
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A versatile route to the mixed p-toluenesulphonic carboxylic anhydrides (1) via the reaction of tetra-n-butylammonium carboxylate (2) with p-toluenesulphonyl chloride in a neutral medium is described.Some of the synthetic applications of the proposed method are described.
- Kumar, Arvind,Srivastava, Nivedita,Mital, Alka
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p. 606 - 607
(2007/10/02)
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- A CONVENIENT SYNTHESIS OF AMIDES FROM CARBOXYLIC ACIDS AND PRIMARY AMINES
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A convenient method for the formation of carboxamides from carboxylic acids and primary amines in the presence of molecular sieves is described.This process is very chemoselective.
- Cossy, J.,Pale-Grosdemange, C.
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p. 2771 - 2774
(2007/10/02)
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- Rapid Acid-catalysed and Uncatalysed Hydration of Ketenimines
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The rates of hydration of a series of ketenimines (9) have been examined in water (μ 1.0; 25 deg) over the pH range 2-13.Three mechanisms of hydration to the amides (8) were noted: (a) general acid catalysis by proton transfer from H3O(1+) in the pH range 2-7 (giving kH3O(1+)/kD3O(1+) 2.65); (b) general acid catalysis by H2O at pH > 7 (where kH2O/kD2O = 4.8); (c) rate determining HO(1-) attack.The last mechanism was only shown by N-arylketenimines, e.g. (9e); other N-alkylketenimines continue to react by rate-determining proton transfer from water even at pH 13.This result is confirmed by the incorporation of just one deuterium when (9a) reacted in acidic or basic D2O, while the deuteriated ketenimine (9f) does not loose the label on the reaction in water.Substituent effects are parallel for reactions involving H(1+) transfer from H3O(1+) or H2O; the major effects are obtained on changing substituents at carbon (the protonation site).For example, replacement of C-H by C-Me reduces the reactivity by 10-20-fold, while replacement of C-Me by C-Ph reduces the rate of hydration by >100-fold.Ammonium ions also generally react with ketenimines by rate-determining H(1+) transfer to the ketenimine followed by trapping of the nitrilium ion formed by the free amine.Only with the strongest amine base studied (piperidine) does direct nucleophilic attack on the ketenimine compete.
- McCarthy, Daniel G.,Hegarty, Anthony F.
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p. 579 - 591
(2007/10/02)
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