- Near-Ambient-Temperature Dehydrogenative Synthesis of the Amide Bond: Mechanistic Insight and Applications
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The current existing methods for the amide bond synthesis via acceptorless dehydrogenative coupling of amines and alcohols all require high reaction temperatures for effective catalysis, typically involving reflux in toluene, limiting their potential practical applications. Herein, we report a system for this reaction that proceeds under mild conditions (reflux in diethyl ether, boiling point 34.6 °C) using ruthenium PNNH complexes. The low-temperature activity stems from the ability of Ru-PNNH complexes to activate alcohol and hemiaminals at near-ambient temperatures through the assistance of the terminal N-H proton. Mechanistic studies reveal the presence of an unexpected aldehyde-bound ruthenium species during the reaction, which is also the catalytic resting state. We further utilize the low-temperature activity to synthesize several simple amide bond-containing commercially available pharmaceutical drugs from the corresponding amines and alcohols via the dehydrogenative coupling method.
- Kar, Sayan,Xie, Yinjun,Zhou, Quan Quan,Diskin-Posner, Yael,Ben-David, Yehoshoa,Milstein, David
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p. 7383 - 7393
(2021/06/30)
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- Metal-Free Transamidation of Secondary Amides by N-C Cleavage
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Transamidation reactions represent a fundamental chemical process involving conversion of one amide functional group into another. Herein, we report a facile, highly chemoselective method for transamidation of N-tert-butoxycarbonylation (N-Boc) activated secondary amides that proceeds under exceedingly mild conditions in the absence of any additives. Because this reaction is performed in the absence of metals, oxidants, or reductants, the reaction tolerates a large number of useful functionalities. The reaction is compatible with diverse amides and nucleophilic amines, affording the transamidation products in excellent yields through direct nucleophilic addition to the amide bond. The utility of this methodology is highlighted in the synthesis of Tigan, a commercial antiemetic, directly from the amide bond. We expect that this new metal-free transamidation will have broad implications for the development of new transformations involving direct nucleophilic addition to the amide bond as a key step.
- Rahman, Md. Mahbubur,Li, Guangchen,Szostak, Michal
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p. 12091 - 12100
(2019/10/11)
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- Nickel-Catalyzed Phosphine Free Direct N-Alkylation of Amides with Alcohols
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Herein, we developed an operational simple, practical, and selective Ni-catalyzed synthesis of secondary amides. Application of renewable alcohols, earth-abundant and nonprecious nickel catalyst facilitates the transformations, releasing water as byproduct. The catalytic system is tolerant to a variety of functional groups including nitrile, allylic ether, and alkene and could be extended to the synthesis of bis-amide, antiemetic drug Tigan, and dopamine D2 receptor antagonist Itopride. Preliminary mechanistic studies revealed the participation of a benzylic C-H bond in the rate-determining step.
- Das, Jagadish,Banerjee, Debasis
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p. 3378 - 3384
(2018/03/26)
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- REDOX DEHYDRATION COUPLING CATALYSTS AND METHODS RELATED THERETO
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This disclosure relates to synthetic coupling methods using catalytic molecules. In certain embodiments, the catalytic molecules comprise heterocyclic thiolamide, S-acylthiosalicylamide, disulfide, selenium containing heterocycle, diselenide compound, ditelluride compound or tellurium containing heterocycle. Catalytic molecules disclosed herein are useful as catalysts in the transformation of hydroxy group containing compounds to amides, esters, ketones, and other carbon to heteroatom or carbon to carbon transformations.
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Page/Page column 17
(2017/08/01)
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- Efficient fluoride-catalyzed conversion of CO2 to CO at room temperature
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A protocol for the efficient and selective reduction of carbon dioxide to carbon monoxide has been developed. Remarkably, this oxygen abstraction step can be performed with only the presence of catalytic cesium fluoride and a stoichiometric amount of a disilane in DMSO at room temperature. Rapid reduction of CO2 to CO could be achieved in only 2 h, which was observed by pressure measurements. To quantify the amount of CO produced, the reduction was coupled to an aminocarbonylation reaction using the two-chamber system, COware. The reduction was not limited to a specific disilane, since (Ph 2MeSi)2 as well as (PhMe2Si)2 and (Me3Si)3SiH exhibited similar reactivity. Moreover, at a slightly elevated temperature, other fluoride salts were able to efficiently catalyze the CO2 to CO reduction. Employing a nonhygroscopic fluoride source, KHF2, omitted the need for an inert atmosphere. Substituting the disilane with silylborane, (pinacolato)BSiMe2Ph, maintained the high activity of the system, whereas the structurally related bis(pinacolato)diboron could not be activated with this fluoride methodology. Furthermore, this chemistry could be adapted to 13C-isotope labeling of six pharmaceutically relevant compounds starting from Ba13CO 3 in a newly developed three-chamber system.
- Lescot, Camille,Nielsen, Dennis U.,Makarov, Ilya S.,Lindhardt, Anders T.,Daasbjerg, Kim,Skrydstrup, Troels
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supporting information
p. 6142 - 6147
(2014/05/20)
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- An improved process for trimethobenzamide hydrochloride
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An improved process for the preparation of trimethobenzamide hydrochloride conforming to regulatory specification is reported. Specifically, a process for the preparation of trimethobenzamide hydrochloride, which is free from the associated impurities that are normally encountered during coupling of 4-(2-dimethylaminoethoxy)benzyl amine with 3,4,5-trimethoxy benzoic acid is described.
- Neelakandan,Manikandan,Santosha,Prabhakaran
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p. 981 - 984
(2013/08/23)
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- Synthesis, gastrointestinal prokinetic activity and structure-activity relationships of novel N-[[2-(dialkylamino)ethoxy]benzyl]benzamide derivatives
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Novel N-[[2-(dialkylamino)ethoxy]benzyl]benzamide derivatives (II-1-51), derived from the structural modification of metoclopramide (1), were synthesized and examined for their pharmacological activities. Among them, N-[4-[2-(dimethylamino)ethoxy]benzyl]-3,4-dimethoxybenzamide (II-34) which exhibited well balanced gastrointestinal prokinetic and antiemetic activities was selected as a new type of gastrointestinal prokinetic agent.
- Sakaguchi,Nishino,Ogawa,Iwanaga,Yasuda,Kato,Ito
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p. 202 - 211
(2007/10/02)
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