- Ultrafast amidation of esters using lithium amides under aerobic ambient temperature conditions in sustainable solvents
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Lithium amides constitute one of the most commonly used classes of reagents in synthetic chemistry. However, despite having many applications, their use is handicapped by the requirement of low temperatures, in order to control their reactivity, as well as the need for dry organic solvents and protective inert atmosphere protocols to prevent their fast decomposition. Advancing the development of air- and moisture-compatible polar organometallic chemistry, the chemoselective and ultrafast amidation of esters mediated by lithium amides is reported. Establishing a novel sustainable access to carboxamides, this has been accomplished via direct C-O bond cleavage of a range of esters using glycerol or 2-MeTHF as a solvent, in air. High yields and good selectivity are observed while operating at ambient temperature, without the need for transition-metal mediation, and the protocol extends to transamidation processes. Pre-coordination of the organic substrate to the reactive lithium amide as a key step in the amidation processes has been assessed, enabling the structural elucidation of the coordination adduct [{Li(NPh2)(OCPh(NMe2))}2] (8) when toluene is employed as a solvent. No evidence for formation of a complex of this type has been found when using donor THF as a solvent. Structural and spectroscopic insights into the constitution of selected lithium amides in 2-MeTHF are provided that support the involvement of small kinetically activated aggregates that can react rapidly with the organic substrates, favouring the C-O bond cleavage/C-N bond formation processes over competing hydrolysis/degradation of the lithium amides by moisture or air.
- Bole, Leonie J.,Fairley, Michael,García-Alvarez, Joaquín,Hevia, Eva,Kennedy, Alan R.,Main, Laura,Mulks, Florian F.,O'Hara, Charles T.
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p. 6500 - 6509
(2020/07/15)
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- Synthesis of Aliphatic Amides through a Photoredox Catalyzed Radical Carbonylation Involving Organosilicates as Alkyl Radical Precursors
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Alkyl radicals, from primary to tertiary, formed by photocatalyzed oxidation of organosilicates, are involved efficiently in radical carbonylation with carbon monoxide (CO), in the presence of various amines and CCl4, leading to a variety of amides in moderate to good yields. (Figure presented.).
- Cartier, Alex,Levernier, Etienne,Dhimane, Anne-Lise,Fukuyama, Takahide,Ollivier, Cyril,Ryu, Ilhyong,Fensterbank, Louis
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p. 2254 - 2259
(2020/05/06)
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- Mild and Low-Pressure fac-Ir(ppy)3-Mediated Radical Aminocarbonylation of Unactivated Alkyl Iodides through Visible-Light Photoredox Catalysis
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A novel, mild and facile preparation of alkyl amides from unactivated alkyl iodides employing a fac-Ir(ppy)3-catalyzed radical aminocarbonylation protocol has been developed. Using a two-chambered system, alkyl iodides, fac-Ir(ppy)3, amines, reductants, and CO gas (released ex situ from Mo(CO)6), were combined and subjected to an initial radical reductive dehalogenation generating alkyl radicals, and a subsequent aminocarbonylation with amines affording a wide range of alkyl amides in moderate to excellent yields.
- Chow, Shiao Y.,Stevens, Marc Y.,?kerbladh, Linda,Bergman, Sara,Odell, Luke R.
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supporting information
p. 9155 - 9161
(2016/07/14)
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- Mild and selective Et2Zn-catalyzed reduction of tertiary amides under Hydrosilylation conditions
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Diethylzinc (Et2Zn) can be used as an efficient and chemoselective catalyst for the reduction of tertiary amides under mild reaction conditions employing cost-effective polymeric silane (PMHS) as the hydride source. Crucial for the catalytic activity was the addition of a substoichiometric amount of lithium chloride to the reaction mixture. A series of amides containing different additional functional groups were reduced to their corresponding amines, and the products were isolated in good-to-excellent yields.
- Kovalenko, Oleksandr O.,Volkov, Alexey,Adolfsson, Hans
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supporting information
p. 446 - 449
(2015/03/05)
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- Water solvent method for esterification and amide formation between acid chlorides and alcohols promoted by combined catalytic amines: Synergy between N-methylimidazole and N,N,N′,N′-tetramethylethylenediamine (TMEDA)
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An efficient method for esterification between acid chlorides and alcohols in water as solvent has been developed by combining the catalytic amines, N-methylimidazole and N,N,N′,N′-tetramethylethylenediamine (TMEDA). The present Schotten-Baumann-type reaction was performed by maintaining the pH at around 11.5 using a pH controller to prevent the decomposition of acid chlorides and/or esters and to facilitate the condensation. The choice of catalysts (0.1 equiv.) was crucial: the combined use of N-methylimidazole and TMEDA exhibited a dramatic synergistic effect. The catalytic amines have two different roles: (i) N-methylimidazole forms highly reactive ammonium intermediates with acid chlorides and (ii) TMEDA acts as an effective HCl binder. The production of these intermediates was rationally supported by a careful 1H NMR monitoring study. Related amide formation was also achieved between acid chlorides and primary or secondary amines, including less nucleophilic or water-soluble amines such as 2-(or 4-)chloroaniline, the Weinreb N-methoxyamine, and 2,2-dimethoxyethanamine.
- Nakatsuji, Hidefumi,Morita, Jun-Ichi,Misaki, Tomonori,Tanabe, Yoo
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p. 2057 - 2062
(2007/10/03)
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- Azirine/oxindole ring enlargement via amidinium intermediates
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A novel general method for the synthesis of oxindoles, namely the 'azirine/oxindole ring enlargement via amidinium-intermediates' has been established: the reaction of 2H-azirin-3-amines 1 with BF3· OEt2 in THF solution at -78° leads
- Mekhael, Maged K. G.,Bienz, Stefan,Linden, Anthony,Heimgartner, Heinz
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p. 2385 - 2404
(2007/10/03)
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- Diethylphosphine oxide (DEPO): High-yielding and facile preparation of indolones in water
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(Matrix presented) Indolones are prepared in excellent yield at 80°C in water by radical reaction (aryl radical formation, hydrogen atom abstraction, cyclization, and rearomatization) mediated by the reagent diethylphosphine oxide (DEPO). The reaction fea
- Khan, Tanweer A.,Tripoli, Regis,Crawford, James J.,Martin, Concepcion G.,Murphy, John A.
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p. 2971 - 2974
(2007/10/03)
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- Palladium-Catalyzed Inter- and Intramolecular α-Arylation of Amides. Application of Intramolecular Amide Arylation to the Synthesis of Oxindoles
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2A palladium-catalyzed α-arylation of amides is reported. Intermolecular arylation of N,N-dimethylamides and lactams occurs using aryl halides, silylamide base, and a palladium catalyst. Intramolecular arylation of N-(2-halophenyl)amides occurs using alkoxide base and a palladium catalyst. The palladium catalyst was formed in situ from Pd(dba)2 (dba = trans,trans-dibenzylidene acetone) and BINAP (2,2′-bis(diphenylphosphino)-1,1′-binaphthalene). Although the intermolecular arylation of amides is less general than that reported previously for ketones, unfunctionalized and electron-rich aryl halides gave α-arylamides in 48-75% yield and N-methyl-α-phenylpyrrolidinone in 49% yield. These reactions provided the highest yields yet reported for regioselective amide arylations. Intramolecular amide arylation of 2-bromoanilides gave oxindoles in 52-82% yield. Mono- and disubstituted acetanilides gave 1,3-di- and 1,3,3-trisubstituted oxindoles. The use of dioxane, rather than THF, solvent was important for some of the amide arylations.
- Shaughnessy, Kevin H.,Hamann, Blake C.,Hartwig, John F.
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p. 6546 - 6553
(2007/10/03)
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- Non-toxic ligands in samarium diiodide-mediated cyclizations
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Samarium diiodide-mediated cyclizations of aryl radicals carried out in the presence of several nitrogen ligands (triethylamine, 1,8-diazabyciclo[5.4.0]undec-7-ene and 1,1-3,3-Tetramethylguanidine) are described. The yields and the selectivities observed are comparable to the ones obtained by using hexamethylphosphoramide.
- Cabri, Walter,Candiani, Ilaria,Colombo, Maristella,Franzoi, Luigi,Bedeschi, Angelo
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p. 949 - 952
(2007/10/02)
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