| 1. |
- Malmgren, Joel, 1985-, et al.
(författare)
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C-2 Selective Arylation of Indoles with Heterogeneous Nanopalladium and Diaryliodonium Salts
- 2014
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Ingår i: Chemistry - A European Journal. - Weinheim : Wiley. - 0947-6539 .- 1521-3765. ; 20:42, s. 13531-13535
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Tidskriftsartikel (refereegranskat)abstract
- A simple and efficient method to prepare synthetically useful 2-arylindoles is presented, using a heterogeneous Pd catalyst and diaryliodonium salts in water under mild conditions. A remarkably low leaching of metal catalyst was observed under the applied conditions. The developed protocol is highly C-2 selective and tolerates structural variations both in the indole and in the diaryliodonium salt. Arylations of both NH indoles and N-protected indoles with ortho-substituted, electron-rich, electron-deficient, or halogenated diaryliodonium salts were achieved to give the desired products in high to excellent isolated yields within 6 to 15 h at room temperature or 40 °C.
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| 2. |
- Nagendiran, Anuja, 1986-
(författare)
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Catalytic reactions with palladium supported on mesocellular foam : Applications in hydrogenation, isomerization, and C-C bond forming reactions
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The major part of this thesis concerns the development of catalytic methodologies based on palladium nanoparticles immobilized on aminopropyl-functionalized siliceous mesocellular foam (Pd0-AmP-MCF). The catalytic activity of the precursor to the nanocatalyst, PdII-AmP-MCF is also covered by this work.In the first part the application of Pd0-AmP-MCF in Suzuki-Miyaura cross-coupling reactions and transfer hydrogenation of alkenes under microwave irradiation is described. Excellent reactivity was observed and a broad range of substrates were tolerated for both transformations. The Pd0-AmP-MCF exhibited high recyclability as well as low metal leaching in both cases.The aim of the second part was to evaluate the catalytic efficiency of the closely related PdII-AmP-MCF for cycloisomerization of various acetylenic acids. The catalyst was able to promote formation of lactones under mild conditions using catalyst loadings of 0.3 - 0.5 mol% at temperatures of up to 50 oC in the presence of Et3N. By adding 1,4-benzoquinone to the reaction, the catalyst could be recycled four times without any observable decrease in the activity.The selective arylation of indoles at the C-2 position using Pd-AmP-MCF and symmetric diaryliodonium salts is presented in the third part. These studies revealed that Pd0-AmP-MCF was more effective than PdII-AmP-MCF for this transformation. Variously substituted indoles as well as diaryliodonium salts were tolerated, giving arylated indoles in high yields within 15 h at 20 - 50 oC in H2O. Only very small amounts of Pd leaching were observed and in this case the catalyst exhibited moderate recyclability.The final part of the thesis describes the selective hydrogenation of the C=C in different α,β-unsaturated systems. The double bond was efficiently hydrogenated in high yields both under batch and continuous-flow conditions. High recyclability and low metal leaching were observed in both cases.
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| 3. |
- Nagendiran, Anuja, et al.
(författare)
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Cycloisomerization of Acetylenic Acids to gamma-Alkylidene Lactones using a Palladium(II) Catalyst Supported on Amino-Functionalized Siliceous Mesocellular Foam
- 2014
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 79:3, s. 1399-1405
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Tidskriftsartikel (refereegranskat)abstract
- Cycloisomerization of various gamma-acetylenic acids to their corresponding gamma-alkylidene lactones by the use of a heterogeneous Pd(II) catalyst supported on amino-functionalized siliceous mesocellular foam is described. Substrates containing terminal as well as internal alkynes were cyclized in high to excellent yields within 2-24 h under mild reaction conditions. The protocol exhibited high regio- and stereoselectivity, favoring the exo-dig product with high Z selectivity. Moreover, the catalyst displayed excellent stability under the employed reaction conditions, as demonstrated by its good recyclability and low leaching.
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| 4. |
- Nagendiran, Anuja, et al.
(författare)
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Mild and Selective Catalytic Hydrogenation of the C=C Bond in a,b-Unsaturated Carbonyl Compounds Using Supported Palladium Nanoparticles
- 2016
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 22:21, s. 7184-7189
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Tidskriftsartikel (refereegranskat)abstract
- Chemoselective reduction of the C=C bond in a variety of α,β-unsaturated carbonyl compounds using supported palladium nanoparticles is reported. Three different heterogeneous catalysts were compared using 1 atm of H2: 1) nano-Pd on a metal–organic framework (MOF: Pd0-MIL-101-NH2(Cr)), 2) nano-Pd on a siliceous mesocellular foam (MCF: Pd0-AmP-MCF), and 3) commercially available palladium on carbon (Pd/C). Initial studies showed that the Pd@MOF and Pd@MCF nanocatalysts were superior in activity and selectivity compared to commercial Pd/C. Both Pd0-MIL-101-NH2(Cr) and Pd0-AmP-MCF were capable of delivering the desired products in very short reaction times (10–90 min) with low loadings of Pd (0.5–1 mol %). Additionally, the two catalytic systems exhibited high recyclability and very low levels of metal leaching.
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| 5. |
- Nagendiran, Anuja, et al.
(författare)
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Nanopalladium-catalyzed conjugate reduction of Michael acceptors - application in flow
- 2016
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Ingår i: Green Chemistry. - : Royal Society of Chemistry. - 1463-9262 .- 1463-9270. ; 18:9, s. 2632-2637
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Tidskriftsartikel (refereegranskat)abstract
- A continuous-flow approach towards the selective nanopalladium-catalyzed hydrogenation of the olefinic bond in various Michael acceptors, which could lead to a greener and more sustainable process, has been developed. The nanopalladium is supported on aminofunctionalized mesocellular foam. Both aromatic and aliphatic substrates, covering a variation of functional groups such as acids, aldehydes, esters, ketones, and nitriles were selectively hydrogenated in high to excellent yields using two different flow-devices (H-Cube (R) and Vapourtec). The catalyst was able to hydrogenate cinnamaldehyde continuously for 24 h (in total hydrogenating 19 g cinnanmaldehyde using 70 mg of catalyst in the H-cube (R)) without showing any significant decrease in activity or selectivity. Furthermore, the metal leaching of the catalyst was found to be very low (ppb amounts) in the two flow devices.
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| 6. |
- Nagendiran, Anuja
(författare)
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Transition metal-catalysis: Applications of dynamic kinetic resolution in total synthesis and developments of novel methodologies using heterogeneous Pd catalysts
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The first part of the thesis describes a general and efficient route for the enantioselective synthesis of various α-substituted ketones and their corresponding lactones. The two key steps in this synthesis are the ruthenium and CALB-catalyzed dynamic kinetic resolution (DKR) which provided the exocyclic acetates in high yields and excellent enantioselectivity and the subsequent Cu-catalyzed α-allylic substitution giving the corresponding α-substituted products with inversed stereochemistry in high yields. This synthetic route was applied to the synthesis of the naturally occurring (R)-10-methyl-6-undecanolide, via subsequent oxidative cleavage and Baeyer-Villiger oxidation.In the second part, a new microwave-assisted methodology using a heterogeneous Pd nanocatalyst for Suzuki cross-couplings and hydrogenation of alkenes is presented. The catalytic system proved to be compatible with a wide range of functional groups and heteroatoms. In general, excellent yields were obtained within 45 min for the Suzuki cross-couplings and within 30 min for the hydrogenation reactions. The catalyst exhibited high recyclability with a low leaching in both cases.A novel method to prepare γ-alkylidene lactones from alkynoic acids mediated by a heterogeneous Pd(II) catalyst is described in the last part of the thesis. The protocol proved to be highly stereo- and regioselective, affording the 5-exo-dig lactone as the single product in all cases. In general, internal alkynes were cyclized in high to excellent yields within 3 hours using 0.3 mol% of catalyst loading. For internal alkynes, the catalyst loading had to be increased to 0.5 mol% along with prolonged reaction times and elevated temperatures in order to obtained high yields. The catalyst showed some recyclability with low leaching.
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| 7. |
- Oschmann, Michael, et al.
(författare)
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Efficient 1,3-Oxazolidin-2-one Synthesis through Heterogeneous Pd-II-Catalyzed Intramolecular Hydroamination of Propargylic Carbamates
- 2019
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 25:25, s. 6295-6299
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we present an operationally simple protocol for the cycloisomerization of propargylic carbamates in which a heterogeneous catalyst consisting of Pd species immobilized on amino-functionalized siliceous mesocellular foam (Pd-II-AmP-MCF) is used. This Pd nanocatalyst displayed high efficiency at low catalyst loading and reaction temperatures, which allowed for the efficient and mild synthesis of a wide range of 1,3-oxazolidin-2-one derivatives and related compounds. Moreover, it proved possible to re-use the Pd nanocatalyst for several reactions, although a gradual decrease in activity was observed in the subsequent cycles.
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| 8. |
- Verho, Oscar, et al.
(författare)
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Application of Pd Nanoparticles Supported on Mesoporous Hollow Silica Nanospheres for the Efficient and Selective Semihydrogenation of Alkynes
- 2016
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Ingår i: ChemCatChem. - : Wiley-VCH Verlagsgesellschaft. - 1867-3880 .- 1867-3899. ; 8:4, s. 773-778
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Tidskriftsartikel (refereegranskat)abstract
- Herein, the preparation of a heterogeneous catalyst consisting of 1-2nm sized Pd nanoparticles supported on amino-functionalized mesoporous hollow silica nanospheres and its use for the semihydrogenation of mono- and disubstituted alkynes is reported. By utilizing this Pd nanocatalyst together with the green poisoning agent DMSO, high yields of the desired alkenes could be achieved, while suppressing the degree of over-reduction to alkanes. To our delight, the Pd nanocatalyst displayed remarkable chemoselectivity towards the alkyne moiety, allowing the transformation to be carried out in the presence of other reducible functionalities, such as halogens, carbonyl, and nitro groups.
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| 9. |
- Verho, Oscar, et al.
(författare)
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Mesoporous silica nanoparticles applied as a support for Pd and Au nanocatalysts in cycloisomerization reactions
- 2014
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Ingår i: APL Materials. - : AIP Publishing. - 2166-532X. ; 2:11, s. 113316-
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Tidskriftsartikel (refereegranskat)abstract
- Ultra-small mesoporous silica nanoparticles (MSNs) have been synthesized at room temperature with particle sizes ranging from 28 to 45 nm. These MSNs have been employed as heterogeneous supports for palladium and gold nanocatalysts. The colloidal nature of the MSNs is highly useful for catalytic applications as it allows for better mass transfer properties and a more uniform distribution of the nanocatalysts in solution. The two nanocatalysts were evaluated in the cycloisomerization of alkynoic acids and demonstrated to produce the corresponding alkylidene lactones in good to excellent yields under mild conditions. In addition to their high activity, the catalysts exhibit low degree of metal leaching and straight-forward recycling, which highlight the practical utility of MSNs as supports for nanocatalysts. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
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| 10. |
- Verho, Oscar, et al.
(författare)
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Mild and Selective Hydrogenation of Nitro Compounds using Palladium Nanoparticles Supported on Amino-Functionalized Mesocellular Foam
- 2014
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Ingår i: ChemCatChem. - Weinheim : Wiley. - 1867-3880 .- 1867-3899. ; 6:11, s. 3153-3159
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Tidskriftsartikel (refereegranskat)abstract
- We present the utilization of a heterogeneous catalyst comprised of Pd nanoparticles supported on aminopropyl-functionalized siliceous mesocellular foam (Pd-0-AmP-MCF) for the selective hydrogenation of aromatic, aliphatic, and heterocyclic nitro compounds to the corresponding amines. In general, the catalytic protocol exclusively affords the desired amine products in excellent yields within short reaction times with the reactions performed at room temperature under ambient pressure of H-2. Moreover, the reported Pd nanocatalyst displayed excellent structural integrity for this transformation as it could be recycled multiple times without any observable loss of activity or leaching of metal. In addition, the Pd nanocatalyst could be easily integrated into a continuous-flow device and used for the hydrogenation of 4-nitroanisole on a 2.5 g scale, where the product p-anisidine was obtained in 95% yield within 2 h with a Pd content of less than 1 ppm.
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