| 1. |
- Buitrago, Elina, et al.
(författare)
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Efficient and Selective Hydrosilylation of Carbonyls Catalyzed by Iron Acetate and N-Hydroxyethylimidazolium Salts
- 2012
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Ingår i: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 354:1, s. 217-222
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Tidskriftsartikel (refereegranskat)abstract
- Aromatic aldehydes, along with aryl alkyl, heteroaryl alkyl, and dialkyl ketones were efficiently reduced to their corresponding primary and secondary alcohols, respectively, in high yields, using the commercially available and inexpensive polymeric silane, polymethylhydrosiloxane (PMHS), as reducing agent. The reaction is catalyzed by in situ generated iron complexes containing hydroxyethyl-functionalized NHC ligands. Turnover frequencies up to 600 h−1 were obtained
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| 2. |
- Lundberg, Helena, et al.
(författare)
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Catalytic amide formation from non-activated carboxylic acids and amines
- 2014
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Ingår i: Chemical Society Reviews. - : Royal Society of Chemistry (RSC). - 0306-0012 .- 1460-4744. ; 43:8, s. 2714-2742
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Forskningsöversikt (refereegranskat)abstract
- The amide functionality is found in a wide variety of biological and synthetic structures such as proteins, polymers, pesticides and pharmaceuticals. Due to the fact that synthetic amides are still mainly produced by the aid of coupling reagents with poor atom-economy, the direct catalytic formation of amides from carboxylic acids and amines has become a field of emerging importance. A general, efficient and selective catalytic method for this transformation would meet well with the increasing demands for green chemistry procedures. This review covers catalytic and synthetically relevant methods for direct condensation of carboxylic acids and amines. A comprehensive overview of homogeneous and heterogeneous catalytic methods is presented, covering biocatalysts, Lewis acid catalysts based on boron and metals as well an assortment of other types of catalysts.
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| 3. |
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| 4. |
- Lundberg, Helena, et al.
(författare)
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Mechanistic Elucidation of Zirconium-Catalyzed Direct Amidation
- 2017
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 139:6, s. 2286-2295
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism of the zirconium-catalyzed condensation of carboxylic acids and amines for direct formation of amides was studied using kinetics, NMR spectroscopy, and DFT calculations. The reaction is found to be first order with respect to the catalyst and has a positive rate dependence on amine concentration. A negative rate dependence on carboxylic acid concentration is observed along with S-shaped kinetic profiles under certain conditions, which is consistent with the formation of reversible off-cycle species. Kinetic experiments using reaction progress kinetic analysis protocols demonstrate that inhibition of the catalyst by the amide product can be avoided using a high amine concentration. These insights led to the design of a reaction protocol with improved yields and a decrease in catalyst loading. NMR spectroscopy provides important details of the nature of the zirconium catalyst and serves as the starting point for a theoretical study of the catalytic cycle using DFT calculations. These studies indicate that a dinuclear zirconium species can catalyze the reaction with feasible energy barriers. The amine is proposed to perform a nucleophilic attack at a terminal eta(2)-carboxylate ligand of the zirconium catalyst, followed by a C-O bond cleavage step, with an intermediate proton transfer from nitrogen to oxygen facilitated by an additional equivalent of amine. In addition, the DFT calculations reproduce experimentally observed effects on reaction rate, induced by electronically different substituents on the carboxylic acid.
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| 5. |
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| 6. |
- Lundberg, Helena, et al.
(författare)
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Zirconium catalyzed amide formation without water scavenging
- 2019
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Ingår i: Applied organometallic chemistry. - : Wiley. - 0268-2605 .- 1099-0739. ; 33:9
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Tidskriftsartikel (refereegranskat)abstract
- A scalable homogeneous metal-catalyzed protocol for direct amidation of carboxylic acids is presented. The use of 2-10 mol% of the commercially available Zr(Cp)(2)(OTf)(2)center dot THF results in high yields of amides at moderate temperature, using an operationally convenient reaction protocol that circumvents the use of water scavenging techniques.
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| 7. |
- Margalef, Jessica, et al.
(författare)
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Third-Generation Amino Acid Furanoside-Based Ligands from d-Mannose for the Asymmetric Transfer Hydrogenation of Ketones : Catalysts with an Exceptionally Wide Substrate Scope
- 2016
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Ingår i: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 358:24, s. 4006-4018
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Tidskriftsartikel (refereegranskat)abstract
- A modular ligand library of -amino acid hydroxyamides and thioamides was prepared from 10 different N-tert-butyloxycarbonyl-protected -amino acids and three different amino alcohols derived from 2,3-O-isopropylidene--d-mannofuranoside. The ligand library was evaluated in the half-sandwich ruthenium- and rhodium-catalyzed asymmetric transfer hydrogenation of a wide array of ketone substrates, including simple as well as sterically demanding aryl alkyl ketones, aryl fluoroalkyl ketones, heteroaromatic alkyl ketones, aliphatic, conjugated and propargylic ketones. Under the optimized reaction conditions, secondary alcohols were obtained in high yields and in enantioselectivities up to >99%. The choice of ligand/catalyst allowed for the generation of both enantiomers of the secondary alcohols, where the ruthenium-hydroxyamide and the rhodium-thioamide catalysts act complementarily towards each other. The catalytic systems were also evaluated in the tandem isomerization/asymmetric transfer hydrogenation of racemic allylic alcohols to yield enantiomerically enriched saturated secondary alcohols in up to 98% ee. Furthermore, the catalytic tandem -alkylation/asymmetric transfer hydrogenation of acetophenones and 3-acetylpyridine with primary alcohols as alkylating and reducing agents was studied. Secondary alcohols containing an elongated alkyl chain were obtained in up to 92% ee.
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| 8. |
- Rabten, Wangchuk, et al.
(författare)
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Catalytic Water Oxidation by a Molecular Ruthenium Complex : Unexpected Generation of a Single-Site Water Oxidation Catalyst
- 2015
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 54:10, s. 4611-4620
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Tidskriftsartikel (refereegranskat)abstract
- The increasing energy demand calls for the development of sustainable energy conversion processes. Here, the splitting of H2O to O-2 and H-2, or related fuels, constitutes an excellent example of solar-to-fuel conversion schemes. The critical component in such schemes has proven to be the catalyst responsible for mediating the four-electron oxidation of H2O to O-2. Herein, we report on the unexpected formation of a single-site Ru complex from a ligand envisioned to accommodate two metal centers. Surprising N-N bond cleavage of the designed dinuclear ligand during metal complexation resulted in a single-site Ru complex carrying a carboxylate amide motif. This ligand lowered the redox potential of the Ru complex sufficiently to permit H2O oxidation to be carried out by the mild one-electron oxidant [Ru(bpy)(3)](3+) (bpy = 2,2'-bipyridine). The work thus highlights that strongly electron-donating ligands are important elements in the design of novel, efficient H2O :oxidation catalysts.
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| 9. |
- Shatskiy, Andrey, et al.
(författare)
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Ruthenium-Catalyzed Asymmetric Transfer Hydrogenation of Propargylic Ketones
- 2015
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Ingår i: ChemCatChem. - : Wiley. - 1867-3880 .- 1867-3899. ; 7:23, s. 3818-3821
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Tidskriftsartikel (refereegranskat)abstract
- The asymmetric transfer hydrogenation of alpha,beta-propargyl ketones catalyzed by an in situ formed ruthenium-hydroxyamide complex was explored. The acetylenic alcohols were isolated in good to excellent yields with excellent ee values (typically >90%) after short reaction times at room temperature.
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| 10. |
- Slagbrand, Tove, et al.
(författare)
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An Efficient One-pot Procedure for the Direct Preparation of 4,5-Dihydroisoxazoles from Amides
- 2017
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Ingår i: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 359:11, s. 1990-1995
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Tidskriftsartikel (refereegranskat)abstract
- A Mo(CO)(6) (molybdenumhexacarbonyl) catalyzed reductive functionalization of amides to afford 5-amino substituted 4,5-dihydroisoxazoles is presented. The reduction of amides generates reactive enamines, which upon the addition of hydroximinoyl chlorides and base undergoes a 1,3-dipolar cycloaddition reaction that gives access to the desired heterocyclic compounds. The transformation of amides is highly chemoselective and tolerates functional groups such as nitro, nitriles, esters, and ketones. Furthermore, a versatile scope of 4,5-dihydroisoxazoles derived from a variety of hydroximinoyl chlorides and amides is demonstrated.
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| 11. |
- Slagbrand, Tove, et al.
(författare)
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Transformation of Amides into Highly Functionalized Triazolines
- 2017
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 7:3, s. 1771-1775
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Tidskriftsartikel (refereegranskat)abstract
- Triazoles and triazolines are important classes of heterocyclic compounds known to exhibit biological activity. Significant focus has been given to the development of synthetic approaches for the preparation of triazoles, and they are today easily obtainable through a large variety of protocols. The number of synthetic procedures for the formation of triazolines, on the other hand, is limited and further research in this field is required. The protocol presented here gives access to a broad scope of 1,4,5-substituted 1,2,3-triazolines through a one-pot transformation of carboxamides. The two-step procedure involves a Mo(CO)6-catalyzed reduction of tertiary amides to afford the corresponding enamines, followed by in situ cycloaddition of organic azides to form triazolines. The amide reduction is chemoselective and allows for a wide variety of functional groups such as esters, ketones, aldehydes, and imines to be tolerated. Furthermore, a modification of this one-pot procedure gives access to the corresponding triazoles. The chemically stable amide functionality is demonstrated to be an efficient synthetic handle for the formation of highly substituted triazolines or triazoles.
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| 12. |
- Tinnis, Fredrik, et al.
(författare)
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Asymmetric transfer hydrogenation of ketones catalyzed by rhodium complexes containing amino acid triazole ligands
- 2010
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Ingår i: Organic and biomolecular chemistry. - : Royal Society of Chemistry. - 1477-0520 .- 1477-0539. ; 8:20, s. 4536-4539
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Tidskriftsartikel (refereegranskat)abstract
- Active and selective catalysts for the asymmetric reduction of ketones, under transfer hydrogenation conditions, were obtained by combining [RhCl2Cp*](2), with a series of L-amino acid thioamide ligands functionalized with 1,2,3-triazoles. The obtained secondary alcohol products were formed with up to 93% ee.
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| 13. |
- Tinnis, Fredrik, 1976-
(författare)
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Catalytic Formation of Amides
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The amide functionality is a highly important chemical bond, found in a great number of synthetic products such as pharmaceuticals, polymers and agrochemicals. The focus of this thesis has been directed towards efficient, mild and environmentally friendly methods for amide formations. The first part is devoted to the investigation of a Lewis acid catalyzed protocol for direct condensation of non-activated carboxylic acids and amines. ZrCl4 was found to be a highly active catalyst and a low catalytic loading enabled for high yields of secondary and tertiary amides under relatively mild conditions. The second part of the thesis describes our investigations towards a catalytic method for primary amides. We demonstrated that the transformation was feasible by performing minor alterations to the previous Lewis acid based procedure. A variety of primary amides could be obtained in high yields by the use of carbamates, as a non-gaseous source of ammonia in combination with carboxylic acids and catalytic amounts of TiCl4 or ZrCl4. Furthermore, the protocol was extended to include catalytic formation of N,N-dimethylamides from non-activated carboxylic acids.The use of immobilized metal nanoparticles as heterogeneous catalysts has emerged as a highly investigated research area. The final chapter of this thesis deals with the successful application of an immobilized Pd nanocatalyst for amide formation via the aminocarbonylation reaction of aryl iodides. The Pd0-AmP-MCF catalyst was found to operate through a “release and catch” mechanism, in which PdII species were released into the solution and then re-deposited onto the support after completion of the reaction. It was discovered that the combination of aryl halide and amine was the cause of the leaching, and furthermore that the homogeneous Pd species catalyzed the aminocarbonylation reaction. A selection of aryl iodides were evaluated using 2 mol% of Pd0-AmP-MCF under atmospheric pressure of CO, and the corresponding amides were obtained in good to high yields.
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| 14. |
- Tinnis, Fredrik, et al.
(författare)
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Chemoselective Reduction of Tertiary Amides under Thermal Control: Formation of either Aldehydes or Amines
- 2016
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 55:14, s. 4562-4566
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Tidskriftsartikel (refereegranskat)abstract
- The chemoselective reduction of amides in the presence of other more reactive reducible functional groups is a highly challenging transformation, and successful examples thereof are most valuable in synthetic organic chemistry. Only a limited number of systems have demonstrated the chemoselective reduction of amides over ketones. Until now, the aldehyde functionality has not been shown to be compatible in any catalytic reduction protocol. Described herein is a [Mo(CO)6]-catalyzed protocol with an unprecedented chemoselectivity and allows for the reduction of amides in the presence of aldehydes and imines. Furthermore, the system proved to be tunable by variation of the temperature, which enabled for either C−O or C−N bond cleavage that ultimately led to the isolation of both amines and aldehydes, respectively, in high chemical yields.
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| 15. |
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| 16. |
- Tinnis, Fredrik, 1976-, et al.
(författare)
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Efficient Palladium-Catalyzed Aminocarbonylation of Aryl Iodides Using Palladium Nanoparticles Dispersed on Siliceous Mesocellular Foam
- 2014
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Ingår i: Chemistry - A European Journal. - Weinheim : Wiley-VCH Verlag GmbH & Co. KGaA. - 0947-6539 .- 1521-3765. ; 20:20, s. 5885-5889
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Tidskriftsartikel (refereegranskat)abstract
- A highly dispersed nanopalladium catalyst supported on mesocellular foam (MCF), was successfully used in the heterogeneous catalysis of aminocarbonylation reactions. During the preliminary evaluation of this catalyst it was discovered that the supported palladium nanoparticles exhibited a “release and catch” effect, meaning that a minor amount of the heterogeneous palladium became soluble and catalyzed the reaction, after which it re-deposited onto the support.
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| 17. |
- Tinnis, Fredrik, et al.
(författare)
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Metal-Free N-Arylation of Secondary Amides at Room Temperature
- 2015
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 17:11, s. 2688-2691
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Tidskriftsartikel (refereegranskat)abstract
- The arylation of secondary acyclic amides has been achieved with diaryliodonium salts under mild and metal-free conditions. The methodology has a wide scope, allows synthesis of tertiary amides with highly congested aryl moieties, and avoids the regioselectivity problems observed in reactions with (diacetoxyiodo)benzene.
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| 18. |
- Tinnis, Fredrik, et al.
(författare)
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Ruthenium catalyzed asymmetric transfer hydrogenation employing novel bidentate abnormal NHC ligands
- 2011
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- N-Heterocyclic carbenes (NHCs) have been successfully employed as ligands in iridium, rhodium and ruthenium catalyzed transfer hydrogenation reactions. However, there are few reports on the use of catalysts containing chiral NHC ligands for this particular transformation. Furthermore, to the best of our knowledge there are no reports on the use of catalysts based on abnormal NHC ligands in asymmetric transfer hydrogenations. In this work we have prepared novel chiral bidentate NHCs that have the potential for an abnormal binding mode to transitionmetals. Ruthenium complexes of these ligands were employed in the asymmetric transfer hydrogenation of ketones in 2-propanol.
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| 19. |
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| 20. |
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| 21. |
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| 22. |
- Trillo, Paz, et al.
(författare)
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Facile preparation of pyrimidinediones and thioacrylamides via reductive functionalization of amides
- 2017
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 53:65, s. 9159-9162
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Tidskriftsartikel (refereegranskat)abstract
- The development of an efficient protocol for the reductive functionalization of amides into pyrimidinediones and amino-substituted thioacrylamides is presented. Enamines are generated in a highly chemoselective amide hydrosilylation reaction catalyzed by molybdenum hexacarbonyl in combination with 1,1,3,3-tetramethyldisiloxane. The direct addition of either isocyanate or isothiocyanate generates the corresponding pyrimidinediones and 3-aminothioacrylamides in high yields.
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| 23. |
- Trillo, Paz, et al.
(författare)
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Mild Reductive Functionalization of Amides into N-Sulfonylformamidines
- 2017
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Ingår i: ChemistryOpen. - : WILEY-V C H VERLAG GMBH. - 2191-1363. ; 6:4, s. 484-487
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Tidskriftsartikel (refereegranskat)abstract
- The development of a protocol for the reductive functionalization of amides into N-sulfonylformamidines is reported. The one-pot procedure is based on a mild catalytic reduction of tertiary amides into the corresponding enamines by the use of Mo(CO)(6) (molybdenum hexacarbonyl) and TMDS (1,1,3,3-tetramethyldisiloxane). The formed enamines were allowed to react with sulfonyl azides to give the target compounds in moderate to good yields.
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| 24. |
- Volkov, Alexey, et al.
(författare)
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Catalytic Reductive Dehydration of Tertiary Amides to Enamines under Hydrosilylation Conditions
- 2014
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 16:3, s. 680-683
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Tidskriftsartikel (refereegranskat)abstract
- Tertiary amides are efficiently reduced to their corresponding enamines under hydrosilylation conditions, using a transition-metal-free catalytic protocol based on t-BuOK (5 mol %) and (MeO)(3)SiH or (EtO)(3)SiH as the reducing agent. The enamines were formed with high selectivity in good-to-excellent yields.
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| 25. |
- Volkov, Alexey, et al.
(författare)
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Chemoselective reduction of carboxamides
- 2016
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Ingår i: Chemical Society Reviews. - : Royal Society of Chemistry. - 0306-0012 .- 1460-4744. ; 45:24, s. 6685-6697
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Forskningsöversikt (refereegranskat)abstract
- The reduction of amides gives access to a wide variety of important compounds such as amines, imines, enamines, nitrites, aldehydes and alcohols. The chemoselective transformation into these functional groups is challenging due to the intrinsic stability of the amide bond; nevertheless, the ability to reduce highly stable carboxamides selectively in the presence of sensitive functional groups is of high synthetic value for academic and industrial chemists. Hydride-based reagents such as LiAlH4 or diboranes are today the most commonly used compounds for amide reductions, and apart from the substantial amount of waste generated using these methods, they lack tolerance to most other functional groups. This tutorial review provides an overview of the recent progress made in the development of chemoselective protocols for amide reduction and gives an insight to their advantages and drawbacks.
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| 26. |
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