- Direct Amidation of Esters by Ball Milling**
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The direct mechanochemical amidation of esters by ball milling is described. The operationally simple procedure requires an ester, an amine, and substoichiometric KOtBu and was used to prepare a large and diverse library of 78 amide structures with modest to excellent efficiency. Heteroaromatic and heterocyclic components are specifically shown to be amenable to this mechanochemical protocol. This direct synthesis platform has been applied to the synthesis of active pharmaceutical ingredients (APIs) and agrochemicals as well as the gram-scale synthesis of an active pharmaceutical, all in the absence of a reaction solvent.
- Barreteau, Fabien,Battilocchio, Claudio,Browne, Duncan L.,Godineau, Edouard,Leitch, Jamie A.,Nicholson, William I.,Payne, Riley,Priestley, Ian
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supporting information
p. 21868 - 21874
(2021/09/02)
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- Switching from biaryl formation to amidation with convoluted polymeric nickel catalysis
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A stable, reusable, and insoluble poly(4-vinyl-pyridine) nickel catalyst (P4VP-NiCl2) was prepared through the molecular convolution of poly(4-vinylpyridine) (P4VP) and nickel chloride. We proposed a coordination structure of the Ni center in the precatalyst based on elemental analysis and Ni K-edge XANES, and we confirmed that it is consistent with Ni K-edge EXAFS. The Suzuki?Miyaura-type coupling of aryl halides and arylboronic esters proceeded using P4VP-NiCl2 (0.1 mol % Ni) to give the corresponding biaryl compounds in up to 94% yield. Surprisingly, when the same reaction of aryl halides and arylboronic acid/ester was carried out in the presence of amides, the amidation proceeded predominantly to give the corresponding arylamides in up to 99% yield. In contrast, the reaction of aryl halides and amides in the absence of arylboronic acid/ester did not proceed. P4VP-NiCl2 successfully catalyzed the lactamization for preparing phenanthridinone. P4VP-NiCl2 was reused five times without significant loss of catalytic activity. Pharmaceuticals, natural products, and biologically active compounds were synthesized efficiently using P4VPNiCl2 catalysis. Nickel contamination in the prepared pharmaceutical compounds was not detected by ICP-MS analysis. The reaction was scaled to multigrams without any loss of chemical yield. Mechanistic studies for both Suzuki?Miyaura and amidation were performed.
- Sen, Abhijit,Dhital, Raghu N.,Sato, Takuma,Ohno, Aya,Yamada, Yoichi M.A.
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p. 14410 - 14418
(2020/12/21)
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- TBHP-mediated highly efficient dehydrogenative cross-oxidative coupling of methylarenes with acetanilides
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A TBHP-mediated dehydrogenative cross-oxidative-coupling approach has been developed for the synthesis of N-arylbenzamides from methylarenes and acetanilides. This cross-coupling method is free of transition metal catalysts and ligands, and no extra organic solvents are required, which make it an useful and attractive strategy for the straightforward construction of C-N bonds. Besides, this conversion is an important complement to the conventional C-N forming strategies.
- Chen, Cui,Liu, Weibing,Zhou, Peng
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supporting information
p. 2250 - 2255
(2016/11/17)
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- Effective nitration of anilides and acrylamides by tert-butyl nitrite
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Nitro compounds are important intermediates in synthetic organic chemistry and the chemical industry. Herein, the efficient copper-catalyzed [10% Cu(NO3)2·3H2O] nitration of anilides was developed by using TBN (tert-butyl nitrite) as a nitrating reagent to give the corresponding nitro-substituted aromatic products in good to excellent yields. The use of TBN also led to the selective nitration of acrylamides at room temperature to afford only the (E) isomer of the nitration product. A series of anilides and acrylamides with a broad array of functional groups were well-tolerated by this procedure. This synthetic method has many advantages, which include inexpensive starting materials, mild reaction conditions, a fast reaction rate, and high yields. A mechanistic investigation indicates that a nitro radical, which is generated from the thermal homolysis of TBN, is involved in the two nitration processes. The efficient nitration of both anilides and acrylamides was achieved by using TBN (tert-butyl nitrite) as a metal-free nitrating reagent. This synthetic method has many advantages such as mild reaction conditions, a fast reaction rate, good to excellent yields, and a broad substrate scope. Our investigation indicates that a nitro radical is involved in the reaction mechanism.
- Ji, Yi-Fei,Yan, Hong,Jiang, Qi-Bai
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p. 2051 - 2060
(2015/03/18)
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- Synthesis of amides through an oxidative amidation of tetrazoles with aldehydes under transition-metal-free conditions
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A simple, inexpensive and efficient one-pot synthesis of amides was achieved in good yields via the direct oxidative amidation of tetrazoles with aldehydes under transition-metal-free conditions.
- Du, Juan,Luo, Kai,Zhang, Xiuli
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p. 54539 - 54546
(2015/01/09)
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- Direct synthesis of amides from coupling of alcohols and amines catalyzed by ruthenium(II) thiocarboxamide complexes under aerobic conditions
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Four octahedral ruthenium(II) thiocarboxamide complexes of the general formula [RuClCO(AsPh3)2(L)] (L = N-substituted pyridine-2-thiocarboxamide) incorporating carbonyl and triphenylarsine have been synthesized from the reaction of 1 equiv of ruthenium precursor [RuHClCO(AsPh3)3] with 1 equiv of thiocarboxamide ligands in refluxing ethanol in the presence of base. All the new complexes have been fully characterized by means of elemental analysis, IR, UV-vis, and NMR spectral methods. Molecular structures of all the complexes were determined by X-ray crystallography, which confirm the coordination mode of thiocarboxamide and reveal the presence of a distorted octahedral geometry around the Ru ion. All the ruthenium(II) thiocarboxamide complexes were generated as highly efficient catalysts for synthesis of secondary or tertiary amides by coupling of amines and alcohols with low catalyst loading, and the maximum yield was obtained up to 97%. The coupling reaction can be readily carried out under mild aerobic conditions, and release of water is the only byproduct. Further, the effect of substituents of the ligand, solvents, reaction temperature, time, and catalyst loading on the catalytic activity of the complexes has been investigated. A plausible mechanism is proposed for the synthesis of amides via hemiaminal as intermediate through an oxidation of an alcohol to aldehyde.
- Sindhuja, Elangovan,Ramesh, Rengan,Balaji, Sundarraman,Liu, Yu
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p. 4269 - 4278
(2014/12/09)
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- Copper-catalyzed synthesis of benzoxazoles via a regioselective C-H functionalization/C-O bond formation under an air atmosphere
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(Chemical Equation Presented) An efficient method for the synthesis of functionalized benzoxazoles is described that involves a copper(II)-catalyzed regioselective C-H functionalization/C-O bond formation protocol. The use of dichlorobenzene as a solvent at 160°C allows the use of air as the terminal oxidant in the catalytic synthesis of benzoxazoles in a process that has high functional group tolerance. The presence of a directing group at the meta position markedly improves the reaction efficacy and a variety of 7-substituted benzoxazoles are selectively produced under mild reaction conditions. The mechanism of the reaction is also discussed in this report.
- Ueda, Satoshi,Nagasawa, Hideko
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supporting information; experimental part
p. 4272 - 4277
(2009/09/08)
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