- Amide rotation trajectories probed by symmetry
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Amide rotation of peptidyl-prolyl fragments is an important factor in backbone structure organization of proteins. Computational studies have indicated that this rotation preferentially proceeds through a defined transition-state structure (syn/exo). Here, we complement the computational findings by determining the amide bond rotation barriers for derivatives of the two symmetric proline analogues, meso and racemic pyrrolidine-2,5-dicarboxylic acids. The rotations around these residues represent syn/exo-syn/exo and anti/endo-syn/exo hybrid transition states for the meso and racemic diastereomer, respectively. The rotation barriers are lower for the former rotation by about 9 kJ mol-1 (aqueous medium), suggesting a strong preference for the syn/exo (clockwise) rotation over the anti/endo (anticlockwise) rotation. The results show that both hybrid rotation processes are enthalpically driven but respond differently to solvent polarity changes due to the different transition state dipole-dipole interactions.
- Kubyshkin, Vladimir,Budisa, Nediljko
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Read Online
- IrIII-Catalyzed direct syntheses of amides and esters using nitriles as acid equivalents: A photochemical pathway
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An unprecedented IrIII[df(CF3)ppy]2(dtbbpy)PF6-catalyzed simple photochemical process for direct addition of amines and alcohols to the relatively less reactive nitrile triple bond is described herein. Various amides and esters are synthesized as the reaction products, with nitriles being the acid equivalents. A mini-library of different types of amides and esters is made using this mild and efficient process, which uses only 1 mol% of photocatalyst under visible light irradiation (λ = 445 nm). The reaction strategy is also efficient for gram-scale synthesis.
- Talukdar, Ranadeep
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supporting information
p. 5303 - 5308
(2020/04/17)
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- Environmentally benign decarboxylative: N-, O-, and S-Acetylations and acylations
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An operationally simple and general method for acetylation and acylation of a wide variety of substrates (amines, alcohols, phenols, thiols, and hydrazones) has been reported. Meldrum's acid and its derivatives have been used as an air-stable, non-volatile, cost-effective, and easy to handle acetylating/acylating agent. Easily separable byproducts (CO2 and acetone) allowed the isolation of analytically pure acetylated products without the requirement of work-up and any chromatography. This journal is
- Ghosh, Santanu,Purkait, Anisha,Jana, Chandan K.
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supporting information
p. 8721 - 8727
(2020/12/30)
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- An organocatalytic C-C bond cleavage approach: A metal-free and peroxide-free facile method for the synthesis of amide derivatives
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A facile organocatalytic approach has been devised towards the synthesis of amide derivatives using 1,3-dicarbonyls as easily available acyl-sources under peroxide-free reaction conditions. This transformation was accomplished by the cleavage of the C-C bond in the presence of TEMPO as an organocatalyst and excludes the use of transition-metals and harsh reaction conditions. A broad range of substrates with diverse functional groups were well tolerated and delivered the products in high yields.
- Vodnala, Nagaraju,Gujjarappa, Raghuram,Polina, Saibabu,Satheesh, Vanaparthi,Kaldhi, Dhananjaya,Kabi, Arup K.,Malakar, Chandi C.
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supporting information
p. 20940 - 20944
(2020/12/31)
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- Synthesis of acetamides using CO2, methanol, H2 and amines
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Herein, we report the synthesis of acetamides from CO2, methanol, H2 and corresponding amines, which is a new route used to synthesize acetamides. It was found that the Rh catalyst with LiI/LiCl as promoters could effectively catalyze this reaction. Interestingly, no ligand was required and amine substrates played a role in accelerating the reaction.
- Zhang, Jingjing,Qian, Qingli,Wang, Ying,Asare Bediako, Bernard Baffour,Cui, Meng,Yang, Guanying,Han, Buxing
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supporting information
p. 233 - 237
(2019/01/28)
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- Synthesis of Benzofurans and Benzoxazoles through a [3,3]-Sigmatropic Rearrangement: O-NHAc as a Multitasking Functional Group
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The synthesis of heterocycles relies heavily on diverse sigmatropic rearrangements triggered by the cleavage of X-Y (X, Y = C, O, N, S, I) bonds. However, a unified rearrangement approach for constructing heterocyclic libraries is highly desirable. Encouraged by computational analysis of [3,3]-sigmatropic rearrangements, we can now rapidly synthesize oxa-heterocycles by treating N-phenoxyacetamides (Ph-ONHAc) with compounds containing an sp-hybridized carbon. The generality of the process is illustrated by the late-stage diversification of natural products, including estrone and an approved drug. A combination of experimental and computational studies revealed that the reactions proceed through a facile Claisen-like [3,3]-sigmatropic rearrangement/annulation process.
- Yan, Dingyuan,Jiang, Heming,Sun, Wenxue,Wei, Wei,Zhao, Jing,Zhang, Xinhao,Wu, Yun-Dong
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supporting information
p. 1646 - 1653
(2019/09/04)
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- Synthesis of 4-Vinylmorpholine Based on Acetylene
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It has been shown that from the possible methods for the synthesis of 4-vinylmorpholine, the vinylation of morpholine with acetylene remains acceptable. A technologically accessible method for vinylation of morpholine with acetylene at atmospheric pressure was developed.
- Asratyan,Bagdasaryan,Markosyan, A. Dzh.,Badalyan,Attaryan
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p. 342 - 345
(2018/05/15)
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- Manganese-Catalyzed Direct Conversion of Ester to Amide with Liberation of H2
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A simple and efficient Mn-catalyzed acylation of amines is achieved using both acyl and alkoxy functions of unactivated esters with the liberation of molecular hydrogen as a sole byproduct. The present protocol provides an atom-economical and sustainable route for the synthesis of amides from esters by employing an earth-abundant manganese salt and inexpensive phosphine-free tridentate ligand.
- Mondal, Akash,Subaramanian, Murugan,Nandakumar, Avanashiappan,Balaraman, Ekambaram
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supporting information
p. 3381 - 3384
(2018/06/11)
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- Cu(II)-Mediated keto C(sp3)-H bond α-acyloxylation of N, N-dialkylamides with aromatic carboxylic acids
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The selective oxidative coupling of aromatic carboxylic acids with the C(sp3)-H bond adjacent to the keto group of alkylamides has been developed by employing a low cost copper source. This provides an efficient approach for synthesis of O-benzoylglycolamides. The protocol displayed good functional group tolerance. A broad range of benzoic acids directly coupled with alkylamides to afford a variety of O-benzoylglycolamides in moderate to good yields. In addition, a reasonable radical mechanism was proposed based on EPR experiments.
- Li, Wenjing,Yin, Changzhen,Yang, Xiao,Liu, Hailong,Zheng, Xueli,Yuan, Maolin,Li, Ruixiang,Fu, Haiyan,Chen, Hua
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supporting information
p. 7594 - 7599
(2017/09/27)
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- Amine-mediated synthesis of amides from 1,3-dicarbonyl compounds through a domino diazo transfer/aminolysis process
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The dual role of amines as both catalysts and substrates for the synthesis of diazo compounds or carboxamides from 1,3-dicarbonyl compounds is described herein. In the presence of a suitable diazo transfer agent, primary and cyclic secondary amines act as basic catalysts for the diazo transfer reaction to malonates, β-keto esters, and β-diketones. Depending on the structure of the 1,3-dicarbonyl compound and the nucleophilicity of the amine, the resulting α-diazo-β-keto ester undergoes cleavage of the acyl group to give amides. A multifunctionalized γ-azido-α-diazo-β-keto ester was cleanly prepared in good yields by this one-pot protocol under practical and safe conditions, being employed in a Knoevenagel-type condensation with aromatic aldehydes to give densely functionalized diazo azido compounds. Further treatment of these unsaturated γ-azido-α-diazo-β-keto esters with primary amines readily furnished the corresponding α-azidocinnamamides in high yields, which were used in the synthesis of novel indole-2-carboxamides through the rhodium-catalyzed intramolecular C–H insertion.
- Costin, Taíssa A.,Dutra, Luiz G.,Bortoluzzi, Adailton J.,Sá, Marcus M.
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p. 4549 - 4559
(2017/07/11)
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- Copper-Manganese Spinel Oxide Catalyzed Synthesis of Amides and Azobenzenes via Aminyl Radical Cations
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A highly efficient Cu-Mn-catalyzed process for the aminolysis of esters was developed. Also, the catalyst promoted the self- And cross-dehydrogenative coupling of anilines to generate symmetrical and unsymmetrical azobenzenes, respectively. The reactions were performed under neutral conditions with an inexpensive catalyst, gave high yields, and offered wide functional group tolerance. Spinel tap: A novel facet of aminyl radical cation reactivity with esters for the synthesis of amides is presented. The developed method also gives access to symmetrical and unsymmetrical azobenzenes. The reactions are performed under neutral conditions with an inexpensive catalyst, give high yields, and have a wide functional group tolerance.
- Sultan, Shaista,Kumar, Manjeet,Devari, Shekaraiah,Mukherjee, Debaraj,Ali Shah, Bhahwal
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p. 703 - 707
(2016/03/05)
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- The Effect of Ring-Size on the Anodic Oxidation of 'Cyclic Amides' in Methanol
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The anodic oxidation of three 'cyclic amides' of type N-acylazacycloalkanes [5- (I), 6- (II) and 7-membered (III) rings] has been studied in methanol under constant current electrolysis, at C anodes and in the presence of various supporting electrolytes, and different concentrations of substrates. Four major products were formed in good yields by all three substrates, namely N-acyl, α-azacycloalkenes, N-acyl, α-methoxyazacycloalkanes, N-acyl, α-methoxy, α'-azacycloalkenes and N-acyl, α,α′-dimethoxyazacycloalkanes. The relative ratios among products and selectivity were found to be highly dependent on the nature of the electrolyte used, and to a lesser extent on substrate concentration. In terms of ring-size effect it was found that the rate of oxidation and current efficiency (yield) was in the order: I > II > III. Also the latter two behaved similarly (but different from I) when various supporting electrolytes were used.
- Golub, Tatiana,Becker, James Y.
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p. 207 - 214
(2016/05/24)
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- Generation and trapping of ketenes in flow
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Ketenes were generated by the thermolysis of alkoxyalkynes under flow conditions, and then trapped with amines and alcohols to cleanly give amides and esters. For a 10 min reaction time, temperatures of 180, 160, and 140 °C were required for >95% conversion of EtO, iPrO, and tBuO alkoxyalkynes, respectively. Variation of the temperature and flow rate with inline monitoring of the output by IR spectroscopy allowed the kinetic parameters for the conversion of 1-ethoxy-1-octyne to be easily estimated (Ea = 105.4 kJ/mol). Trapping of the in-situ-generated ketenes by alcohols to give esters required the addition of a tertiary amine catalyst to prevent competitive [2+2] addition of the ketene to the alkoxyalkyne precursor.
- Henry, Cyril,Bolien, David,Ibanescu, Bogdan,Bloodworth, Sally,Harrowven, David C.,Zhang, Xunli,Craven, Andy,Sneddon, Helen F.,Whitby, Richard J.
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p. 1491 - 1499
(2015/03/04)
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- Direct Preparation of Amides from Amine Hydrochloride Salts and Orthoesters: A Synthetic and Mechanistic Perspective
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The conversion of a wide range of primary and secondary aliphatic and a few arylamine hydrochloride salts to their corresponding acetamides with trimethyl orthoacetate is described. Mechanistic studies using NMR and gas chromatography-mass spectrometry techniques indicate these reactions proceed via an O-methylimidate intermediate that undergoes in situ demethylation by chloride, affording the corresponding acetamides. Synthetically, this reaction represents a practical, high-yielding protocol with a simple workup for the rapid conversion of amine hydrochloride salts to acetamides.
- Di Grandi, Martin J.,Bennett, Caitlin,Cagino, Kristen,Muccini, Arnold,Suraci, Corey,Saba, Shahrokh
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supporting information
p. 2601 - 2607
(2015/11/28)
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- Transamidation of carboxamides catalyzed by Fe(III) and water
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The highly efficient transamidation of several primary, secondary, and tertiary amides with aliphatic and aromatic amines (primary and secondary) is described. The reaction is performed in the presence of a 5 mol % concentration of different hydrated salts of Fe(III), and the results show that the presence of water is crucial. The methodology was also applied to urea and phthalimide to demonstrate its versatility and wide substrate scope. An example of its use is an intramolecular application in the synthesis of 2,3-dihydro-5H-benzo[b]-1,4- thiazepin-4-one, which is the bicyclic core of diltiazem and structurally related drugs (Budriesi, R.; Cosimelli, B.; Ioan, P.; Carosati, E.; Ugenti, M. P.; Spisani, R. Curr. Med. Chem. 2007, 14, 279-287). A plausible mechanism that explains the role of water is proposed on the basis of experimental observations and previous mechanistic suggestions for transamidation reactions catalyzed by transition metals such as copper and aluminum. This methodology represents a significant improvement over other existing methods; it can be performed in air and with wet or technical grade solvents.
- Becerra-Figueroa, Liliana,Ojeda-Porras, Andrea,Gamba-Sánchez, Diego
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p. 4544 - 4552
(2014/06/09)
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- Carbonylation of quaternary ammonium salts to tertiary amides using NaCo(CO)4 catalyst
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We reported here the catalytic carbonylation of quaternary ammonium salts under anhydrous condition. Quaternary ammonium salts, a kind of versatile reagents that were widely used in organometallic chemistry, can be carbonylated to tertiary amides by an in situ prepared NaCo(CO)4 catalyst. It was found that the counterions (Cl-, Br-, I-, OTf-) in the quaternary ammonium salts played a significant role in the reaction and tetramethylammonium iodide could give high yield (96%) of N,N-dimethylacetamide (DMAc) with only 0.5 mol% cobalt catalyst. Under optimum conditions, several other quaternary ammonium iodides were also carbonylated to corresponding tertiary amides in moderate to excellent yields. Obviously, these results also give us a special apprehension that Me4NI and other quaternary ammonium salts could be possibly carbonylated to tertiary amides in the carbonylation reaction where they are used as promoters or solvents in most cases. Considering the high activity and moderate to excellent selectivity, this process could be a potential method for the synthesis of certain tertiary amides. Moreover, the cleaving mechanism of CN bonds and the possible catalytic intermediates were discussed in detail.
- Lei, Yizhu,Zhang, Rui,Wu, Qing,Mei, Hui,Xiao, Bo,Li, Guangxing
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p. 120 - 125
(2013/12/04)
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- Palladium-catalyzed carbonylation of quaternary ammonium halides to tertiary amides
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Catalytic carbonylation of quaternary ammonium salts under anhydrous conditions was investigated using palladium catalyst. The carbonylation of tetramethylammonium iodide was chosen as a model reaction and studied systematically. Ligand-free PdCl2 showed efficient catalytic performance for this transformation. A palladium catalyst loading as low as 0.05 mol% was sufficient for high yield (96.9%) of N,N-dimethylacetamide, corresponding to a turnover frequency of 242 h-1. Under optimum conditions, several other quaternary ammonium halides were also carbonylated to corresponding tertiary amides in moderate to excellent yields. The catalytic activity of commercial palladium on activated carbon (Pd/C) catalyst was also evaluated. The Pd/C catalyst exhibited high activity for this carbonylation reaction and could be recycled six times with a slight decrease in activity. Furthermore, mechanistic considerations concerning Pd-catalyzed carbonylation of quaternary ammonium halides were also discussed. Copyright
- Lei, Yizhu,Zhang, Rui,Wu, Linjuan,Wu, Qing,Mei, Hui,Li, Guangxing
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p. 310 - 314
(2014/04/03)
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- Silica-supported boric acid catalyzed synthesis of dihydropyrimidin-2-ones, bis(indolyl)methanes, esters and amides
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Silica-supported boric acid (H3BO3-SiO2) has been established as a green, efficient and recyclable catalyst for the synthesis of dihydropyrimidin-2-ones, bis(indolyl)methanes, and acetylation of alcohols, phenols, amines and thiols under solvent free conditions. The main features of the present method include clean reaction, mild conditions, low loading of environment friendly catalyst and easy workup procedure. The catalyst can be recycled at least five times without any significant loss in activity.
- Kumar, Vishal,Singh, Chitra,Sharma, Upendra,Verma, Praveen K.,Singh, Bikram,Kumar, Neeraj
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- Chemoselective intermolecular α-arylation of amides
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A new approach for the fully chemoselective α-arylation of amides is presented. By means of electrophilic amide activation, aryl groups can be regioselectively introduced α- to amides, even in the presence of esters and alkyl ketones. Mechanistic studies reveal key reaction intermediates and emphasize a remarkably subtle base effect in this transformation. Arylating me softly: A new approach for the fully chemoselective α-arylation of amides has been developed. When electrophilic amide activation is employed, aryl groups can be regioselectively introduced in the position α to the amide, and that even in the presence of esters or alkyl ketones. Mechanistic studies emphasize a remarkably subtle base effect in this transformation.
- Peng, Bo,Geerdink, Danny,Fares, Christophe,Maulide, Nuno
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supporting information
p. 5462 - 5466
(2014/06/09)
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- Selectivities in acylation of primary and secondary amine with diacylaminoquinazolinones and diacylanilines
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The diacylaminoquinazolinones are highly selective acylating agents for primary amines in the presence of secondary amines. The chemoselective N-acetylation reagents have been investigated using 2-substituted N,Ndiacylaminoquinazolinones (DAQs) and 2-substitued-N-diacylanilines (DAAs). Determination of the selectivity ratios have been made by comparison of the crude product in each case with authentic samples of the amide products using NMR spectroscopy. The control experiments in which pairs of amines compete for acetyl chloride show some selectivity but not comparable with that of DAQs and DAAs selectivity. When the DAQs, DAAs and acetyl chloride react with mixtures of pyrrolidine and piperidine, they give amides in the corresponding ratios. The DAQs 1 and 2 react entirely with diethylamine without any competitive reaction with diphenylamine. The high level of chemoselectivity has also been observed when the 1 and 2 react exclusively with the ethanolamine without any competitive reaction with diethanolamine. Moreover, 1 and 2 react with succinimide without any competitive reaction with phthalimide.
- Al-Sehemi, Abdullah G.,Al-Amri, Reem S. Abdul-Aziz,Irfan, Ahmad
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p. 1115 - 1121
(2014/10/15)
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- Overcoming product inhibition in catalysis of the intramolecular Schmidt reaction
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A method for carrying out the intramolecular Schmidt reaction of alkyl azides and ketones using a substoichiometric amount of catalyst is reported. Following extensive screening, the use of the strong hydrogen-bond-donating solvent hexafluoro-2-propanol was found to be consistent with low catalyst loadings, which ranged from 2.5 mol % for favorable substrates to 25 mol % for more difficult cases. Reaction optimization, broad substrate scope, and preliminary mechanistic studies of this improved version of the reaction are described.
- Motiwala, Hashim F.,Fehl, Charlie,Li, Sze-Wan,Hirt, Erin,Porubsky, Patrick,Aube, Jeffrey
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supporting information
p. 9000 - 9009
(2013/07/26)
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- N -acyl DBN tetraphenylborate salts as N -acylating agents
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Air-stable and crystalline N-acyl DBN tetraphenylborate salts have been synthesized from 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and the corresponding acyl chloride in the presence of sodium tetraphenylborate. The salts have been shown to be effective N-acylating agents, reacting with primary amines, secondary amines, and sulfonamides to form the corresponding N-acylated products in good yields. The DBN hydrotetraphenylborate byproduct can be conveniently removed by filtration, providing pure N-acylated products without the need for further purification. The N-acyl DBN tetraphenylborate salts are attractive alternatives to acyl halides as they can be stored in air without decomposition, avoid the production of free acid during acylation reactions, and can be used under more forcing thermal conditions.
- Taylor, James E.,Jones, Matthew D.,Williams, Jonathan M. J.,Bull, Steven D.
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experimental part
p. 2808 - 2818
(2012/04/23)
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- In situ generation and intramolecular schmidt reaction of keto azides in a microwave-assisted flow format
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Go with the flow! A method for conversion of keto halides to lactams by means of sequential azidation and intramolecular Schmidt reaction in a combined flow format is described (see scheme; MWI=microwave irradiation, TFA=trifluoroacetic acid).
- Painter, Thomas O.,Thornton, Paul D.,Orestano, Mario,Santini, Conrad,Organ, Michael G.,Aube, Jeffrey
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supporting information; experimental part
p. 9595 - 9598
(2011/10/04)
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- Synthesis of amides from esters and amines with liberation of H2 under neutral conditions
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Efficient synthesis of amides directly from esters and amines is achieved under mild, neutral conditions with the liberation of molecular hydrogen. Both primary and secondary amines can be utilized. This unprecedented, general, environmentally benign reaction is homogeneously catalyzed under neutral conditions by a dearomatized ruthenium-pincer PNN complex and proceeds in toluene under an inert atmosphere with a high turnover number (up to 1000). PNP analogues do not catalyze this transformation, underlining the crucial importance of the amine arm of the pincer ligand. A mechanism is proposed involving metal-ligand cooperation via aromatization-dearomatization of the pyridine moiety and hemilability of the amine arm.
- Gnanaprakasam, Boopathy,Milstein, David
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supporting information; experimental part
p. 1682 - 1685
(2011/04/22)
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- Synthesis of amide libraries with immobilized HOBt
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Highly reactive N-acylating solid-phase reagents based on macroporous polystyrene-bound 1-hydroxybenzotriazole (P-HOBt) and silica-bound 1-hydroxybenzotriazole (Si-HOBt) were prepared and compared for reactivity by synthesis of small combinatorial libraries of acetamides and benzamides.
- Vokkaliga, Smitha,Jeong, Jeannie,Lacourse, William R.,Kalivretenos, Aristotle
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supporting information; experimental part
p. 2722 - 2724
(2011/06/19)
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- Efficient one-pot synthesis of N-substituted 2-aminochromones, their benzo-fused derivatives, and diaminobenzodipyrandiones of two new structural classes
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N-Substituted 2-aminochromones and their benzo-fused derivatives were obtained in high yields by a new one-pot synthesis, starting from the appropriate acetamides, salicylic acid or its benzo-fused derivatives, and phosphoryl chloride. By the same reaction, from suitable dihydroxybenzenedicarboxylic acids, some compounds of two new structural classes, 2,7-diaminobenzo[1,2-b:4,5-b']dipyran-4,9-diones and 2,8-diamino-4H,6H-benzo[1,2-b:5,4-b']dipyran-4,6-diones, were synthesized. Georg Thieme Verlag Stuttgart.
- Roma, Giorgio,Piras, Daniela,Di Braccio, Mario,Grossi, Giancarlo
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experimental part
p. 849 - 857
(2010/10/02)
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- Direct synthesis of N-acylpyrrolidines from tetrahydrofuran and nitriles of aliphatic and aromatic acids on zeolite catalysts under supercritical conditions
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The tetrahydrofuran-nitrile (CH3CN, n-C4H 9CN, C6H5CN)-zeolite (faujasites, mordenite, beta, pentasils) system and its transformations under supercritical conditions were studied. The feasibility of d
- Usachev,Kalinin,Udal'Tsova,Davydov,Chizhov
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experimental part
p. 94 - 98
(2010/03/24)
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- Proline-rich proteins - Deriving a basis for residue-based selectivity in polyphenolic binding
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1H NMR titration experiments have been used to establish that minimal proline-based models show enhanced binding selectivity towards phenol in CDCl3, relative to other similarly protected amino acid residues. Cooperative binding effects appear to play a role, with sarcosine models affording binding constants to phenol intermediate to those obtained from proline models and other amino acid models. The mechanism for binding, based on DFT calculations and the application of Hunter's molecular recognition toolbox model, cannot be solely attributed to hydrogen bond strength, and appears to be mediated through C-H-π bonds and the rotational freedom of the amide substrate. The Royal Society of Chemistry 2008.
- Croft,Foley
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supporting information; experimental part
p. 1594 - 1600
(2008/10/09)
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- Bi(III) halides as efficient catalysts for the O-acylative cleavage of tetrahydrofurans: An expeditious entry to tetralins
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The mild (DCM/20°C), quantitative, regioselective, O-acylative cleavage of tetrahydrofurans using organic acid halides with catalytic Bi(III) halides is reported. X-ray crystallography is used to rationalise the failure of the reaction in the case of certain crowded acid chlorides, and a useful aspect of chemoselectivity is revealed. The synthetic potential of this reaction is illustrated with a highly efficient O-acylative cleavage/intramolecular alkylation approach to tetralins.
- Coles, Simon J.,Costello, James F.,Draffin, William N.,Hursthouse, Michael B.,Paver, Simon P.
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p. 4447 - 4452
(2007/10/03)
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- Amidine Nitrosation
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The acidic nitrosation chemistry of nine acyclic secondary and tertiary amidines (Ph-N=C(R1)-NR2R3; R1 = H, CH3, Ph; R2, R3 = H, Ph or (CH 3)2 or C(CH2)4) and several N-acylamidines was investigated. The principal nitrosation products were amides derived from the amino moiety and compounds derived from the benzenediazonium ion, which was independently trapped for quantitation in several cases. Tertiary amidines also produce nitrosamines in minor, but significant, yields. The benzamidines did not react, and the N-acylamidines hydrolyzed much more rapidly than they nitrosated. The data support the hypothesis that the reaction occurs by nitrosation on the imino nitrogen, followed by the addition of H 2O to give a tetrahedral intermediate (α-hydroxynitrosamine) for which the main decomposition pathway generates an amide and a diazonium ion. In the case of the pyrrolidine-derived amidines, about 25% of the decomposition results in cleavage of the amine moiety, which nitrosates to give N-nitrosopyrrolidine. Pseudo-first-order rate constants for amidine nitrosation in aqueous acetic acid with excess nitrite at 25 °C ranged from (3 to 106) × 10-5 s-1, while the amidine basicity ranged over 5 pKa units. Rate constants corrected for amidine basicity showed the pyrrolidine derived amidines to be most reactive. The lack of benzamidine nitrosative reactivity is attributed to a very slow rate of H2O additon to the N-nitrosoamidinium ion and reversible nitrosation.
- Loeppky, Richard N.,Yu, Hongbin
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p. 3015 - 3024
(2007/10/03)
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- (Pyridine)(tetrahydroborato)zinc complex mediated acetylation of amines with ethyl acetate
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(Pyridine)(tetrahydroborato)zinc complex, (Py)Zn(BH4)Z, can efficiently perform acetylation of a variety of aliphatic and aromatic amines with ethyl acetate under refluxing THF.
- Zeynizadeh, Behzad,Zahmatkesh, Karam
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p. 801 - 805
(2007/10/03)
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- Efficient chemoselective liquid phase acylation of amines, alcohols and bifunctional compounds over ZSM-35
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ZSM-35, is a medium pore zeolite, has been synthesized using ethylene diamine as organic template. The catalyst is used in the acylation of different amines, alcohols and bifunctional compounds. This material is found to be active and selective acid catalyst, exhibits not only very good activity but also very high chemo-selectivity towards monoacylation of bifunctional compounds. This material is more reactive for smaller organic compounds because of its pore dimension. In case of bifunctional compounds like amino alcohols, amines are selectively acylated at lower temperature.
- Srivastava,Venkatathri
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p. 888 - 891
(2007/10/03)
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- Transacylation of α-Aryl-β-keto Esters
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The acyl group of an α-aryl-β-keto ester was readily transferred to N-, O-, and S-nucleophiles. The transacylation from arylated diethyl 3-oxoglutarate to amines led to unsymmetrical malonic acid amide esters in high yields. The present reaction proceeded under mild conditions without formation of detectable byproducts. Only simple experimental manipulations were required. This reaction was also found to be sensitive to steric factors, which enabled the chemoselective monoacylation of diamines and amino alcohols without any modifications such as protection.
- Nishiwaki, Nagatoshi,Nishida, Daisei,Ohnishi, Tetsuya,Hidaka, Fumie,Shimizu, Satoru,Tamura, Mina,Hori, Kazushige,Tohda, Yasuo,Ariga, Masahiro
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p. 8650 - 8656
(2007/10/03)
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- Stereoselective synthesis of 2-aminocyclobutanols via photocyclization of α-amido alkylaryl ketones: Mechanistic implications for the Norrish/Yang reaction
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A series of chiral N-acylated α-amino p-methylbutyrophenone derivatives 1a-1h was synthesized from α-amino acids via a three-step procedure. These substrates were photolyzed in benzene and gave Norrish II and Norrish I cleavage products as well as the N-acylated 2-aminocyclobutanols that derive from γ-hydrogen abstraction and 1,4-triplet biradical combination (Yang cyclization). The products were formed with characteristic Yang/cleavage ratios. The quantum yields for the photodecomposition of the N-acetyl-protected substrates 1b,e,f were moderate (12-26%); the diastereoselectivities of the cyclobutanol formation were remarkably high for all substrates. High diastereospecificity was observed for the isoleucine derivatives (2S,3S)-1g and allo-(2S,3R)-1g; the Yang reaction dominated the photochemistry of allo-1g, whereas 1g gave preferentially Norrish II cleavage. The role of hydrogen bonding as one of the stereo-directing effects was demonstrated by comparison of the cyclization efficiency of the valine derivative 1e with 1h,i,j. Also, aromatic β-keto esters gave the Yang cyclization products in low yields. The diastereoselectivity of the cyclobutanol formation was rationalized by a three-step mechanism where every step is connected with one distinct stereochemical induction mechanism: (a) diastereoselective hydrogen abstraction, (b) conformational equilibration of the 1,4-tetramethylene biradicals (as calculated by semiempiric methods) controlled by hydrogen bonding, and (c) diastereoselective biradical combination (versus cleavage) influenced by spin-orbit coupling controlled intersystem crossing geometries.
- Griesbeck, Axel G.,Heckroth, Heike
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p. 396 - 403
(2007/10/03)
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- Synthesis of amides from esters and amines under microwave irradiation
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Formamide, primary and secondary amines react with esters in the presence of potassium tert-butoxide under microwave irradiation. Substituted amides are formed in yields (generally more than 70%) much higher than under conventional heating.
- Zradni, Fatima-Zohra,Hamelin, Jack,Derdour, Aicha
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p. 3525 - 3531
(2007/10/03)
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- Kinetic resolution of amines with enantiopure 3-N,N-diacylaminoquinazolin-4(3H)-ones
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The title compounds (DAQs) are chiral when the two N-acyl groups are different because of the absence of rotation around the N-N bond (a chiral axis). Enantiopure DAQs have been obtained by incorporation of a chiral centre in enantiopure form either into the substituent at the Q2-position or into one of the N-acyl groups, or into both, followed by separation of diastereoisomers. This separation is unnecessary in one case because conversion of the N-monoacylaminoquinazolinone (MAQ) into the DAQ is completely diastereoselective. Neither is separation of diastereoisomers necessary with 3-[N,N-di-(S)-2-acetoxypropanoylamino]-2-diphenylmethylquinazolin-4(3H)-one 37a: this DAQ 37a has its N-N bond rendered a chiral axis by the bias in its imide moiety wholly in favour of one exo/endo conformation. The high chemoselectivity exhibited by N,N-diacetyl- or N,N-dibenzoylaminoquinazolinones in reaction with the less hindered of two secondary amines (pyrrolidine in the presence of 1 eq. of piperidine) has a stereoselective counterpart: reaction of the above enantiopure DAQs enantioselectively with racemic amines leading to kinetic resolution. Using 1 eq. of DAQ and 2 eq. of amine, both the derivatised and unreacted amine enantiomers are recovered with high enantiomeric excess (ee) (better than 90% ee in some cases). Some of the higher ees are found in the recovered amides where non-chemoselective attack on both N-acyl groups of the DAQ has occurred: from the opposite configurations of the amine component in the two amides and from the low enantiopurity of the recovered unreacted amine, reaction of each of the N-acyl groups with complementary enantiomers of the amine is occurring (parallel kinetic resolution). Although higher ees are, in general, obtained using secondary amines, high ees are obtained in some cases using 1-phenylethylamine and, in particular, amino acid esters (valine and alanine). The sense of enantioselectivity in the reactions of these DAQs with amines is controlled by the configuration of the N-N axis: replacing the Q group in an N-(S)-2-acetoxypropanoyl-N-acetyl-bearing DAQ by phthalimide, thus eliminating the N-N chiral axis, drastically reduces the level of kinetic resolution.
- Al-Sehemi, Abdullah G.,Atkinson, Robert S.,Fawcett, John
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p. 257 - 274
(2007/10/03)
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- Platinum catalysed hydrolytic amidation of unactivated nitriles
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The platinum(II) complex, [(Me2PO··H··OPMe2)PtH(PMe2OH)], efficiently catalyses the direct conversion of unactivated nitriles to N- substituted amides with both primary and secondary amines. Possible mechanisms for this reaction are discussed and evidence for initial amidine formation is reported. Isolated yields vary from 51-89%. (C) 2000 Elsevier Science Ltd.
- Cobley, Christopher J.,Van Den Heuvel, Marco,Abbadi, Abdelilah,De Vries, Johannes G.
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p. 2467 - 2470
(2007/10/03)
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- A simple route to N,N-dialkyl derivatives of 2-amino-5-thiophenecarboxylates
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Starting from acetamides 4 and using three different routes - via thioacetamides 5, 3-amino-thioacrylamides 7, or 3-chloropropeniminium salts 6 - a series of new N,N-dialkyl derivatives of 2-amino-5-thiophenecarboxylates 10 has been prepared and analytically and spectroscopically characterized.
- Heyde, Cornelia,Zug, Ines,Hartmann, Horst
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p. 3273 - 3278
(2007/10/03)
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- HOBT immobilized on macroporous polystyrene beads: A useful reagent for the synthesis of amides
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Polymer-supported 1-hydroxybenzotriazole (P-HOBT), prepared from macroporous polystyrene beads, was used to synthesize amides from primary and secondary amines.
- Dendrinos, Kleanthis,Jeong, Jeannie,Huang, Wei,Kalivretenos, Aristotle G.
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p. 499 - 500
(2007/10/03)
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- Eclipsed Conformation of the Exocyclic N-CH2 Bond in N-Neopentylpiperidines and the Stereodynamic Consequences As Studied by Dynamic NMR Spectroscopy and Molecular Mechanics Calculations
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The dynamic stereochemistry of a range of N-neopentylpiperidines 1 with an eclipsed N-CH2-t-Bu bond is compared with that of the corresponding range of N-ethylpiperidines 2 with a gauche N-CH2Me bond. By using dynamic NMR spectroscopy, the relative importance of ring inversion, exocyclic bond rotation, and nitrogen inversion are elucidated and barriers are reported and discussed. Minor populations of the neopentyl-axial-eclipsed conformation are detected directly and identified with the help of molecular mechanics calculations. The corresponding N-alkylpyrrolidines are also reported.
- Anderson, J. Edgar,Ijeh, Anthony I.,Storch, Christine,Casarini, Daniele,Lunazzi, Lodovico
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p. 3310 - 3317
(2007/10/03)
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- Novel Two-Step Stereoselective Synthesis of (E)-Enamines and 1-Amino-1,3-dienes from Terminal Alkynes
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(E)-Enamines and 1-amino-1,3-dienes have been prepared by reaction of secondary amines with alk-1-en-1-yl acetates resulting from the ruthenium-catalyzed anti-Markovnikov addition of acetic acid to terminal alkynes and enynes.
- Doucet, Henri,Bruneau, Christian,Dixneuf, Pierre H.
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p. 807 - 808
(2007/10/03)
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- The ortho-substituted N,N-diacetylaniline as a selective acetylating reagent
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Selective acetylation of the less hindered amino group in the presence of the more hindered amino group with the use of 2-trifluoromethyl-N,N-diacetylaniline 2c is described. This acetylation with 2c yielded the corresponding less hindered monoacetamide exclusively, simply, conveniently, and in good yields.
- Murakami, Yasuoki,Kondo, Kazuhiro,Miki, Kazuki,Akiyama, Yoko,Watanabe, Toshiko,Yokoyama, Yuusaku
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p. 3751 - 3754
(2007/10/03)
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- Reactions of thioamides with metal carboxylates in organic media
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Reactions of thioamides with metal carboxylates in organic solvents are described. These processes enable the selective preparation of nitriles, imides or amides depending on the substitution pattern of the starting material. Mechanistic hypotheses supported by experimental evidences, including the unequivocal synthesis of bis(thioacetanilide)mercury(II) as a key reaction intermediate, are also proposed.
- Avalos, Martin,Babiano, Reyes,Cintas, Pedro,Duran, Carlos J.,Higes, Francisco J.,Jimenez, Jose L.,Lopez, Ignacio,Palacios, Juan C.
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p. 14463 - 14480
(2007/10/03)
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- Intramolecular Schmidt reactions of alkyl azides with ketals and enol ethers
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The ketals or enol ethers of 1,5-azidoketones were converted into lactams using a two-stage process. Treatment of the ketals and enol ethers with acid (trifluoroacetic acid, triflic acid, or trimethylsilyl triflate) afforded an oxonium ion which reacted with the tethered azide to give a 1,1-azido-alkoxy intermediate. Bond reorganization led to an iminium ether that was reacted with sodium iodide in acetone to expose the amide products. Seven intramolecular examples proceeding in yields of 68 to ≥95% are reported using dimethyl or diethyl ketals. Attempts using 1,3-dioxolanes and an intermolecular example are also described.
- Mossman, Craig J.,Aube, Jeffrey
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p. 3403 - 3408
(2007/10/03)
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- Acylation of alcohols and amines with vinyl acetates catalyzed by Cp*2Sm(thf)2
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Cp*2Sm(thf)2 was found to be an efficient catalyst for the acylation of alcohols and amines with esters under mild conditions. In the present acylation, vinyl and isopropenyl acetates served as good acylating agents. Thus, a variety of alcohols and amines underwent acylation with vinyl and isopropenyl acetates in the presence of Cp*2Sm(thf)2 to give the corresponding esters and amides in good to excellent yields. This catalytic acylation of alcohols and amines offers an additional useful method by the use of various esters, instead of acid anhydrides and acid chlorides, as acylating agents under very mild conditions.
- Ishii, Yasutaka,Takeno, Mitsuhiro,Kawasaki, Yumi,Muromachi, Akifumi,Nishiyama, Yutaka,Sakaguchi, Satoshi
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p. 3088 - 3092
(2007/10/03)
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- Intramolecular Schmidt reactions of alkyl azides with ketones: Scope and stereochemical studies
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The intramolecular Schmidt reaction of alkyl azides and ketones has been demonstrated. The reaction is proposed to occur via initial attack of an azide on a ketone activated by a variety of protic or Lewis acids, including trifluoroacetic acid, titanium tetrachloride, and others. The resulting azidohydrin undergoes a direct rearrangement to afford the product amide and molecular nitrogen. When cyclic ketones are used, fused bicyclic lactams of types encountered in a wide variety of natural products are obtained. Although the distance allowed between the carbonyl group and the alkyl azide is quite restricted, the reaction is general with respect to the ketone component, including acyclic ketones and cyclic substrates ranging from standard to large ring sizes. The reaction also succeeds with aldehydes, although elimination or hydride migration products compete. In several cases examined the reaction was found to proceed with retention of configuration at the migrating carbon. Competing reactions with β-diketones and α,β-unsaturated ketones were found to predominate over ring expansion.
- Milligan, Gregory L.,Mossman, Craig J.,Aubé, Jeffrey
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p. 10449 - 10459
(2007/10/03)
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- A Mild and Efficient Method for Selective Acetylation of Amines
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Primary and secondary amines were acetylated under mild conditions by means of 3-acetyl-1,3-thiazolidine-2-thione .The reaction was successfully applied to selective acetylation of a primary amino group of diamines containing a primary and a secondary amino groups or exclusive N-acetylation of amino alcohols.Key Words Selective acetylation; 3-Acetyl-1,3-thiazolidine-2-thione.
- Yang, Shyh-Chyun,Wang, Huey-Min,Chen, Ling-Ching
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p. 585 - 588
(2007/10/02)
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- Reaction of Thioamides with Silver Carboxylates in Aprotic Media. A Nucleophilic Approach to the Synthesis of Imides, Amides, and Nitriles.
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Synthesis of nitriles, imides, and amides by reaction of silver carboxylates with unsubstituted, N-substituted, and N,N-disubstituted thiomaides in aprotic media are described.
- Avalos, Martin,Babiano, Reyes,Duran, Carlos J.,Jimenez, Jose L.,Palacios, Juan C.
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p. 477 - 480
(2007/10/02)
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- Synthesis in dry media coupled with microwave irradiation: Application to the preparation of enaminoketones
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β-diketones react with a variety of amines and aminoesters over clay K10 or silica under microwave irradiation in open vessels to give within a few minutes, the corresponding enaminoketones with good yields. According to the reaction conditions acylamines may also result.
- Rechsteiner,Texier-Boullet,Hamelin
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p. 5071 - 5074
(2007/10/02)
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