| 1. |
- Kärkäs, Markus D., 1984-, et al.
(författare)
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Light-Induced Water Oxidation by a Ru complex Containing a Bio-Inspired Ligand
- 2011
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 17:28, s. 7953-7959
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Tidskriftsartikel (refereegranskat)abstract
- The new Ru complex 8 containing the bio-inspired ligand 7 was successfully synthesized and characterized. Complex 8 efficiently catalyzes water oxidation using Ce(IV) and Ru(III) as chemical oxidants. More importantly, this complex has a sufficiently low overpotential to utilize ruthenium polypyridyl-type complexes as photosensitizers.
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| 2. |
- Yuan, Ning, et al.
(författare)
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Investigation of the Deactivation and Reactivation Mechanism of a Heterogeneous Palladium(II) Catalyst in the Cycloisomerization of Acetylenic Acids by In Situ XAS
- 2021
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 11:5, s. 2999-3008
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Tidskriftsartikel (refereegranskat)abstract
- A well-studied heterogeneous palladium(II) catalyst used for the cycloisomerization of acetylenic acids is known to be susceptible to deactivation through reduction. To gain a deeper understanding of this deactivation process and to enable the design of a reactivation strategy, in situ X-ray absorption spectroscopy (XAS) was used. With this technique, changes in the palladium oxidation state and coordination environment could be studied in close detail, which provided experimental evidence that the deactivation was primarily caused by triethylamine-promoted reduction of palladium(II) to metallic palladium nanoparticles. Furthermore, it was observed that the choice of the acetylenic acid substrate influenced the distribution between palladium(II) and palladium(0) species in the heterogeneous catalyst after the reaction. From the mechanistic insight gained through XAS, an improved catalytic protocol was developed that did not suffer from deactivation and allowed for more efficient recycling of the catalyst.
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| 3. |
- Gudmundsson, Arnar, et al.
(författare)
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On the Use of Iron in Organic Chemistry
- 2020
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Ingår i: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 25:6
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Forskningsöversikt (refereegranskat)abstract
- Transition metal catalysis in modern organic synthesis has largely focused on noble transition metals like palladium, platinum and ruthenium. The toxicity and low abundance of these metals, however, has led to a rising focus on the development of the more sustainable base metals like iron, copper and nickel for use in catalysis. Iron is a particularly good candidate for this purpose due to its abundance, wide redox potential range, and the ease with which its properties can be tuned through the exploitation of its multiple oxidation states, electron spin states and redox potential. This is a fact made clear by all life on Earth, where iron is used as a cornerstone in the chemistry of living processes. In this mini review, we report on the general advancements in the field of iron catalysis in organic chemistry covering addition reactions, C-H activation, cross-coupling reactions, cycloadditions, isomerization and redox reactions.
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| 4. |
- Närhi, Katja, et al.
(författare)
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An unexpectedly mild thermal alder-ene-type cyclization of enallenes
- 2006
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 71:7, s. 2914-2917
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Tidskriftsartikel (refereegranskat)abstract
- A mild, thermal Alder-ene reaction of enallenes has been developed. The allenic double bond acts as the "ene" and generates a carbon-carbon bond to an unactivated olefinic "enophile" in DMF at 120 degrees C to give [n.3.0] bicyclic systems (n = 3-5) in good yields. Except for a minor [2 + 2] cycloaddition byproduct, the reaction proceeded with complete atom economy, as there is no requirement of a catalyst or additional reactants, and no waste products are formed in the process.
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| 5. |
- Berner, Simon, et al.
(författare)
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Activity boost of a biomimetic oxidation catalyst by immobilization onto a gold surface
- 2006
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 244:1, s. 86-91
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Tidskriftsartikel (refereegranskat)abstract
- Thiol-functionalized cobalt porphyrins were used as a model system for investigating catalytic activity in homogeneous and heterogeneous oxidation catalysis. Self-assemble monolayers of thiol-functionalized cobalt porphyrins were prepared on a gold surface and served as heterogenous catalysts. These immoblilized molecules prevented the strong inactivation observed for their homogeneous congener. As a result, the turnover number per molecule in heterogeneous catalysis was at least 100 times higher than that of the corresponding homogeneous catalyst. It is atypical for a heterogenized catalyst to outperform its homogeneous congener. The properties of the molecular layers were characterized on the molecular level by means of X-ray photoelectorn spectroscopy (XPS) and scanning tunneling microscopy (STM). The results demonstrate that the performance of these biomimetic catalysts can be dramatically improved if the catalyst arangement can be controlled on the molecular level.
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| 6. |
- Bruneau, Alexandre, et al.
(författare)
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Synthesis of Benzofurans and Indoles from Terminal Alkynes and Iodoaromatics Catalyzed by Recyclable Palladium Nanoparticles Immobilized on Siliceous Mesocellular Foam
- 2017
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 23:52, s. 12886-12891
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we report on the utilization of a heterogeneous catalyst, consisting of Pd nanoparticles supported on a siliceous mesocellular foam (Pd-0-AmP-MCF), for the synthesis of heterocycles. Reaction of o-iodophenols and protected o-iodoanilines with acetylenes in the presence of a Pd nanocatalyst produced 2-substituted benzofurans and indoles, respectively. In general, the catalytic protocol afforded the desired products in good to excellent yields under mild reaction conditions without the addition of ligands. Moreover, the structure of the reported Pd nanocatalyst was further elucidated with extended X-ray absorption fine-structure spectroscopy, and it was proven that the catalyst could be recycled multiple times without significant loss of activity.
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| 7. |
- Deiana, Luca, et al.
(författare)
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Artificial plant cell walls as multi-catalyst systems for enzymatic cooperative asymmetric catalysis in non-aqueous media
- 2021
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 57:70, s. 8814-8817
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Tidskriftsartikel (refereegranskat)abstract
- The assembly of cellulose-based artificial plant cell wall (APCW) structures that contain different types of catalysts is a powerful strategy for the development of cascade reactions. Here we disclose an APCW catalytic system containing a lipase enzyme and nanopalladium particles that transform a racemic amine into the corresponding enantiomerically pure amide in high yield via a dynamic kinetic resolution.
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| 8. |
- Deiana, Luca, et al.
(författare)
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Subtilisin integrated artificial plant cell walls as heterogeneous catalysts for asymmetric synthesis of (S)-amides
- 2023
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 13:29, s. 19975-19980
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Tidskriftsartikel (refereegranskat)abstract
- Subtilisin integrated artificial plant-cell walls (APCWs) were fabricated by self-assembly using cellulose or nanocellulose as the main component. The resulting APCW catalysts are excellent heterogeneous catalysts for the asymmetric synthesis of (S)-amides. This was demonstrated by the APCW-catalyzed kinetic resolution of several racemic primary amines to give the corresponding (S)-amides in high yields with excellent enantioselectivity. The APCW catalyst can be recycled for multiple reaction cycles without loss of enantioselectivity. The assembled APCW catalyst was also able to cooperate with a homogeneous organoruthenium complex, which allowed for the co-catalytic dynamic kinetic resolution (DKR) of a racemic primary amine to give the corresponding (S)-amide in high yield. The APCW/Ru co-catalysis constitutes the first examples of DKR of chiral primary amines when subtilisin is used as a co-catalyst.
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| 9. |
- Eriksson, Kristofer, et al.
(författare)
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Dispersed Gold Nanoparticles Supported in the Pores of Siliceous Mesocellular Foam : A Catalyst for Cycloisomerization of Alkynoic Acids to gamma-Alkylidene Lactones
- 2015
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Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; :10, s. 2250-2255
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Tidskriftsartikel (refereegranskat)abstract
- A versatile approach for the production of dispersed thiol-stabilized gold nanoparticles in the pores of siliceous mesocellular foam (MCF) is described. The reported method is based on an electrochemical oxidation of a gold surface generating oxidative Au-III species, which give rise to a surface-confined redox reaction yielding MCF-supported Au-I thiolates. By reducing the corresponding Au-I-S-MCF species with sodium borohydride, thiol-stabilized gold nanoparticles in the size range of 1-8 nm were obtained as determined by transmission electron microscopy. Elemental analysis indicated an Au loading of 3% (w/w) on the MCF. The surface-confined Au nanoparticles were used to catalyze the cycloisomerization of alkynoic acids to the corresponding -alkylidene lactones in high efficiency and complete 5-exo-dig selectivity under mild reaction conditions.
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| 10. |
- Guđmundsson, Arnar, et al.
(författare)
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Iron(II)-Catalyzed Aerobic Biomimetic Oxidation of Amines using a Hybrid Hydroquinone/Cobalt Catalyst as Electron Transfer Mediator
- 2021
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 60:21, s. 11819-11823
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Tidskriftsartikel (refereegranskat)abstract
- Herein we report the first Fe-II-catalyzed aerobic biomimetic oxidation of amines. This oxidation reaction involves several electron transfer steps and is inspired by biological oxidation in the respiratory chain. The electron transfer from the amine to molecular oxygen is aided by two coupled catalytic redox systems, which lower the energy barrier and improve the selectivity of the oxidation reaction. An iron hydrogen transfer complex was utilized as the substrate-selective dehydrogenation catalyst along with a bifunctional hydroquinone/cobalt Schiff base complex as a hybrid electron transfer mediator. Various primary and secondary amines were oxidized in air to their corresponding aldimines or ketimines in good to excellent yield.
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