- Protocol for Palladium/ N-Heterocyclic Carbene-Catalyzed Suzuki-Miyaura Cross-Coupling of Amides by N-C(O) Activation
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Amides are among the most important and ubiquitous functional groups in organic chemistry and process development. In this Practical Synthetic Procedure, a protocol for the Suzuki-Miyaura cross-coupling of amides by selective N-C(O) bond activation catalyzed by commercially available, air-and moisture-stable palladium/N-heterocyclic carbene (NHC) complexes is described. The procedure described involves [Pd(IPr)(cin)Cl] [IPr = 2,6-(diisopropylphenyl)imidazol-2-ylidene, cin = cinnamyl] at 0.10 mol% at room temperature and is performed on decagram scale. Furthermore, a procedure for the synthesis of amide starting materials is accomplished via selective N-tert-butoxycarbonylation, which is the preferred method over N-Acylation. The present protocol carries advantages of operational simplicity, commercial availability of catalysts, and excellent conversions at low catalyst loadings. The method is generally useful for activation of N-C(O) amide bonds in a broad spectrum of amide precursors. The protocol should facilitate the implementation of amide cross-coupling reactions.
- Lei, Peng,Li, Guangchen,Ling, Yun,An, Jie,Nolan, Steven P.,Szostak, Michal
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- Synthesis of Sulfoxonium Ylides from Amides by Selective N-C(O) Activation
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The direct synthesis of sulfoxonium ylides from amides by selective N-C(O) cleavage is presented. The reaction proceeds through the nucleophilic addition of dimethylsulfoxonium methylide to the amide bond in acyclic twisted amides under exceedingly mild r
- Rahman, Md. Mahbubur,Szostak, Michal
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- Rh-Catalyzed Base-Free Decarbonylative Borylation of Twisted Amides
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We report the rhodium-catalyzed base-free decarbonylative borylation of twisted amides. The synthesis of versatile arylboronate esters from aryl twisted amides is achieved via decarbonylative rhodium(I) catalysis and highly selective N-C(O) insertion. The method is notable for a very practical, additive-free Rh(I) catalyst system. The method shows broad functional group tolerance and excellent substrate scope, including site-selective decarbonylative borylation/Heck cross-coupling via divergent N-C/C-Br cleavage and late-stage pharmaceutical borylation.
- Bie, Fusheng,Liu, Xuejing,Shi, Yijun,Cao, Han,Han, Ying,Szostak, Michal,Liu, Chengwei,Liu, Xuejing,Szostak, Michal,Liu, Chengwei
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- Metal-Free Transamidation of Secondary Amides via Selective N-C Cleavage under Mild Conditions
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Nonplanar, electronically destabilized amides have emerged as powerful intermediates in organic synthesis. We report a highly selective method for transamidation of common secondary amides under mild, metal-free conditions that relies on transient N-selective functionalization to weaken amidic resonance. The combination of rational modification of the amide bond with nucleophilic addition mechanism, and the thermodynamic collapse of the resultant tetrahedral intermediate constitutes a two-step procedure to accomplish a challenging transamidation of secondary amides under mild conditions.
- Liu, Yongmei,Shi, Shicheng,Achtenhagen, Marcel,Liu, Ruzhang,Szostak, Michal
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- Palladium-Catalyzed Aerobic Oxidative Coupling of Amides with Arylboronic Acids by Cooperative Catalysis
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The first fluoride and palladium co-catalyzed conversion of amide to ester through an aerobic oxidative coupling pathway is reported. This new approach presents a practical process that employs easily available oxygen and commercially available arylboronic acids as coupling partners, uses a wide range of N- tosylamides, and proceeds under mild reaction conditions. This protocol demonstrates broad functional group tolerance, and provides an alternative option to synthesize esters from N-tosylamides which obtained by simply N-functionalization of secondary amides.
- Li, Yue,Wu, Hongxiang,Zeng, Zhuo
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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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- 2-Methyltetrahydrofuran (2-MeTHF): A Green Solvent for Pd?NHC-Catalyzed Amide and Ester Suzuki-Miyaura Cross-Coupling by N?C/O?C Cleavage
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The palladium-NHC-catalyzed (NHC=N-heterocyclic carbene) Suzuki-Miyaura cross-coupling of amides and esters via highly chemoselective N?C(O) and O?C(O) cleavage with aryl boronic acids using green, sustainable and eco-friendly 2-methyltetrahydrofuran (2-MeTHF) is reported. A variety of amides and aryl esters were coupled with aryl boronic acids in high to excellent yields. This method employs commercially-available, air- and moisture-stable Pd(II) ?NHC precatalysts. Crucially, the use of 2-MeTHF leads to the highest TON reported to date in amide N?C(O) bond cross-coupling. This operationally-simple protocol was utilized in the synthesis a bioactive ketone intermediate, emphasizing the potential of 2-MeTHF as a green solvent in unconventional amide bond disconnection. Given the tremendous importance of amide bond cross-coupling strategies and the drive to maintain full sustainability in cross-coupling processes, we expect that the synthetic method will be of broad interest.
- Lei, Peng,Ling, Yun,An, Jie,Nolan, Steven P.,Szostak, Michal
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- General Method for the Suzuki-Miyaura Cross-Coupling of Primary Amide-Derived Electrophiles Enabled by [Pd(NHC)(cin)Cl] at Room Temperature
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A general, highly selective method for the room temperature Suzuki-Miyaura cross-coupling of commonly encountered primary benzamides is reported. A combination of site-selective N,N-di-Boc-activation (tert-butoxycarbonyl activation) of the amide nitrogen with practical air- and moisture-stable, well-defined, and highly reactive [Pd(NHC)(cin)Cl] (NHC = N-heterocyclic carbene; cin = cinnamyl) provides a highly effective route to biaryl ketones from primary amides in high yields. For the first time, a TON of >1000 has been achieved in amide acyl cross-coupling.
- Lei, Peng,Meng, Guangrong,Ling, Yun,An, Jie,Nolan, Steven P.,Szostak, Michal
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- A General Method for Two-Step Transamidation of Secondary Amides Using Commercially Available, Air- and Moisture-Stable Palladium/NHC (N-Heterocyclic Carbene) Complexes
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The first general method is reported for transamidation of secondary carboxamides catalyzed by Pd-NHC (NHC = N-heterocyclic carbene) complexes. Commercially available, air- and moisture-stable (NHC)Pd(R-allyl)Cl complexes can effect C-N cross-coupling of a wide range of N-Boc and N-Ts amides, obtained by selective amide N-functionalization, with non-nucleophilic anilines and sterically hindered amines in very good yields. The first use of versatile Pd-NHC complexes as catalysts is represented for transition-metal-catalyzed C(acyl)-N amination of amides by N-C activation.
- Meng, Guangrong,Lei, Peng,Szostak, Michal
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- Ball-milling enables highly selective solvent-free N-tert-butoxycarbonylation for activation of amides
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A ball-milling enabled chemoselective activation of amides via N-tert-butoxycarbonylation catalyzed by 4-dimethylaminopyridine is described under solvent-free conditions. High chemoselectivity with respect to NH acidity of amides has been observed. A one-pot two-step procedure for selective esterification of amides has been demonstrated in model reaction of benzamides with p-cresol and benzyl alcohol.
- Shi, Weijia,Sun, Guoping,Zou, Gang
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supporting information
(2020/07/03)
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- Chemoselective Synthesis of Aryl Ketones from Amides and Grignard Reagents via C(O)-N Bond Cleavage under Catalyst-Free Conditions
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Conversion of a wide range of N-Boc amides to aryl ketones was achieved with Grignard reagents via chemoselective C(O)-N bond cleavage. The reactions proceeded under catalyst-free conditions with different aryl, alkyl, and alkynyl Grignard reagents. α-Ketoamide was successfully converted to aryl diketones, while α,β-unsaturated amide underwent 1,4-addition followed by C(O)-N bond cleavage to provide diaryl propiophenones. N-Boc amides displayed higher reactivity than Weinreb amides with Grignard reagents. A broad substrate scope, excellent yields, and quick conversion are important features of this methodology.
- Sureshbabu, Popuri,Azeez, Sadaf,Muniyappan, Nalluchamy,Sabiah, Shahulhameed,Kandasamy, Jeyakumar
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p. 11823 - 11838
(2019/10/02)
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- Na2CO3-promoted thioesterification via N–C bond cleavage of amides to construct thioester derivatives
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A mild, efficient, and transition-metal-free catalytic strategy is developed to construct thioesters via selective N–C bond cleavage of Boc2-activated primary amides. This strategy is successfully carried out with stoichiometric Na2C
- Tao, Jiasi,Yu, Weijie,Luo, Jin,Wang, Tao,Ge, Wanling,Zhang, Ziwei,Yang, Bingjie,Xiong, Fei
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p. 486 - 492
(2019/11/03)
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- Fluoride-Catalyzed Esterification of Amides
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In recent years, it has been demonstrated that amide carbon–nitrogen bonds can be activated and selectively cleaved using transition metal catalysts. However, these methodologies have been restricted to specific amides; a one-to-one relationship exists between the catalytic system and the amides and also uses large amounts of transition-metal catalysts and ligands. Hence, we now report a general strategy for esterification of common amides using fluoride as a catalyst. This method shows high functional group tolerance, and notably it requires only a slight excess of the alcohol nucleophile, which is a rare case in transition-metal-free amide transformations. Moreover, this approach may provide a new understanding for further studies on esterification of amides and is expected to stimulate the development of alternative methods for direct functionalization of amides.
- Wu, Hongxiang,Guo, Weijie,Daniel, Stelck,Li, Yue,Liu, Chao,Zeng, Zhuo
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supporting information
p. 3444 - 3447
(2018/02/21)
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- A Simple Method for tert-Butoxycarbonylation of Amides
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The tert-butoxycarbonyl (Boc) function was conveniently introduced onto the amide nitrogen in several secondary amides using di-tert-butyl dicarbonate in dry acetonitrile with 4-dimethylaminopyridine as catalyst.Carboxamides with different acyl groups such as formyl, acetyl and benzoyl are presented as well as derivatives of carbamic acid.Examples also include other amide types: sulfonamide, sulfenamide and phosphinamide which were all smoothly converted to the corresponding Boc derivatives under these conditions.The yields were generally excellent and the resulting Boc analogues stable compounds which could be stored for months under ordinary conditions.Some stereochemical and structural aspects of this acylation are also discussed.Bulky substituents in the proximity of the amide moiety significantly retarded the reaction and in some cases no product was detected.For one compound with an activated methine group, C acylation was observed.
- Grehn, Leif,Gunnarsson, Kerstin,Ragnarsson, Ulf
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p. 745 - 750
(2007/10/02)
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- Removal of Formyl, Acetyl, and Benzoyl Groups from Amides with Conversion into the Corresponding t-Butyl Carbamates
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N-Formyl, -acetyl, and -benzoyl groups can be removed from secondary amides with amines under mild conditions after t-butoxycarbonylation, giving acid-labile t-butyl carbamates.
- Grehn, Leif,Gunnarsson, Kerstin,Ragnarsson, Ulf
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p. 1317 - 1318
(2007/10/02)
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