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242 results on '"Kann, Nina"'

1. Carbon–carbon bond formation using aromatics from biomass.

Author

Dunås, Petter, Paterson, Andrew J., Lewis, Simon E., and Kann, Nina

Subjects
CHEMICAL processes, ALDOL condensation, CIRCULAR economy, CONDENSATION reactions, TRANSITION metals
Abstract

The transition to a circular economy requires that we adapt currently used chemical processes to the structurally diverse and often highly oxygenated precursors that are accessible from biomass. In this review, we highlight different examples of carbon–carbon bond formation using aromatics derived from bio-based sources, reported during 2015–2024. Examples of sustainable biomass building blocks include heterocycles such as furfural and hydroxymethylfurfural, obtained from carbohydrates, as well as lignin-based aromatics such as vanillin and eugenol. These have subsequently been applied in a variety of different types of carbon–carbon bond formation, including more classical methods such as aldol condensation and Morita–Baylis–Hillman reactions, but also employing transition metal catalysis, electrochemistry or photochemistry to create new C–C bonds. [ABSTRACT FROM AUTHOR]

Published
2024
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7. Synthesis, characterization and computational evaluation of bicyclooctadienes towards molecular solar thermal energy storage

Author

Quant, Maria, Hillers-Bendtsen, Andreas Erbs, Ghasemi, Shima, Erdélyi, Máté, Wang, Zhihang, Muhammad, Lidiya M., Kann, Nina, Mikkelsen, Kurt V., Moth-Poulsen, Kasper, Quant, Maria, Hillers-Bendtsen, Andreas Erbs, Ghasemi, Shima, Erdélyi, Máté, Wang, Zhihang, Muhammad, Lidiya M., Kann, Nina, Mikkelsen, Kurt V., and Moth-Poulsen, Kasper

Abstract

Molecular solar-thermal energy storage (MOST) systems are based on photoswitches that reversibly convert solar energy into chemical energy. In this context, bicyclooctadienes (BODs) undergo a photoinduced transformation to the corresponding higher energy tetracyclooctanes (TCOs), but the photoswitch system has not until now been evaluated for MOST application, due to the short half-life of the TCO form and limited available synthetic methods. The BOD system degrades at higher temperature via a retro-Diels–Alder reaction, which complicates the synthesis of the compounds. We here report a cross-coupling reaction strategy that enables an efficient synthesis of a series of 4 new BOD compounds. We show that the BODs were able to switch to the corresponding tetracyclooctanes (TCOs) in a reversible way and can be cycled 645 times with only 0.01% degradation. Half-lives of the TCOs were measured, and we illustrate how the half-life could be engineered from seconds to minutes by molecular structure design. A density functional theory (DFT) based modelling framework was developed to access absorption spectra, thermal half-lives, and storage energies which were calculated to be 143–153 kJ mol−1 (0.47–0.51 MJ kg−1), up to 76% higher than for the corresponding norbornadiene. The combined computational and experimental findings provide a reliable way of designing future BOD/TCO systems with tailored properties.

Published
2022
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8. Synthesis, characterization and computational evaluation of bicyclooctadienes towards molecular solar thermal energy storage

Author

Uppsala University, Knut and Alice Wallenberg Foundation, Swedish Research Council, Swedish Energy Agency, European Commission, Quant, Maria, Hillers-Bendtsen, Andreas Erbs, Ghasemi, Shima, Erdelyi, Mate, Wang, Zhihang, Muhammad, Lidiya M, Kann, Nina, Mikkelsen, Kurt V., Moth-Poulsen, Kasper, Uppsala University, Knut and Alice Wallenberg Foundation, Swedish Research Council, Swedish Energy Agency, European Commission, Quant, Maria, Hillers-Bendtsen, Andreas Erbs, Ghasemi, Shima, Erdelyi, Mate, Wang, Zhihang, Muhammad, Lidiya M, Kann, Nina, Mikkelsen, Kurt V., and Moth-Poulsen, Kasper

Abstract

Molecular solar-thermal energy storage (MOST) systems are based on photoswitches that reversibly convert solar energy into chemical energy. In this context, bicyclooctadienes (BODs) undergo a photoinduced transformation to the corresponding higher energy tetracyclooctanes (TCOs), but the photoswitch system has not until now been evaluated for MOST application, due to the short half-life of the TCO form and limited available synthetic methods. The BOD system degrades at higher temperature via a retro-Diels-Alder reaction, which complicates the synthesis of the compounds. We here report a cross-coupling reaction strategy that enables an efficient synthesis of a series of 4 new BOD compounds. We show that the BODs were able to switch to the corresponding tetracyclooctanes (TCOs) in a reversible way and can be cycled 645 times with only 0.01% degradation. Half-lives of the TCOs were measured, and we illustrate how the half-life could be engineered from seconds to minutes by molecular structure design. A density functional theory (DFT) based modelling framework was developed to access absorption spectra, thermal half-lives, and storage energies which were calculated to be 143-153 kJ mol-1 (0.47-0.51 MJ kg-1), up to 76% higher than for the corresponding norbornadiene. The combined computational and experimental findings provide a reliable way of designing future BOD/TCO systems with tailored properties.

Published
2022

12. Solid-phase synthesis of substituted alkynes using the Nicholas reaction

Author

Cassel, Johan A., Leue, Stefanie, Gachkova, Natalie I., and Kann, Nina C.

Subjects
Chemistry, Organic -- Research, Solid state chemistry -- Research, Substitution reactions -- Analysis, Acids, Polymers -- Physiological aspects, Coordination compounds, Biological sciences, Chemistry
Abstract

Research has been conducted on Nicholas reaction on solid phase. Results demonstrate that this reactions involves the reaction of cobalt complexes of polymer-bound alkynols with various nucleophiles in the presence of Lewis acid.

Published
2002

17. Synthesis and characterization of new binuclear Co(0) complexes with diphosphinoamine ligands. A potential approach for asymmetric Pauson-Khand reactions

Author

Gimbert, Yves, Robert, Frederic, Durif, Andre, Averbuch, Marie-Therese, Kann, Nina, and Greene, Andrew E.

Subjects
Ligands -- Research, Cobalt -- Research, Reactivity (Chemistry) -- Research, Coordination compounds -- Research, Biological sciences, Chemistry
Abstract

Research was conducted to examine the synthesis of P-N-P bidentate ligands, assess their pi-acceptor properties in the complexes obtained from phenylacetylene-dicobalt hexacarbonyl and to describe the reactivity of the complexes in the Pauson-Khand reaction. Experimental results show that the important bond distances and angles in the ligands agree with literature values. Findings may help in the design of effective chiral ligands for a new approach to asymmetric Pauson-Khan reactions.

Published
1999

23. A simple, general preparation of S-alkyl and S-aryl ynethiol ethers

Author

Nebois, Pascal, Kann, Nina, and Greene, Andrew E.

Subjects
Ethers -- Research, Organic compounds -- Synthesis, Biological sciences, Chemistry
Abstract

A novel procedure for the high-yield synthesis of S-alkyl and S-aryl ynethiol ethers is described. The one-pot procedure follows the sequence thiol-thiolate-dichloro-enethiol ether-ynethiol ether. Excellent results have been obtained with primary, secondary and tertiary thiols and with thiophenols. The reaction conditions for each synthesis are presented.

Published
1995

24. Asymmetric Horner-Wadsworth-Emmons reactions using meso dialdehydes as substrates

Author

Kann, Nina and Rein, Tobias

Subjects
Nuclear magnetic resonance spectroscopy -- Usage, Esters -- Research, Biological sciences, Chemistry
Abstract

Investigations pertaining to the interactions between meso dialdehydes and chiral Horner-Wadsworth-Emmons reagents elucidate the usefulness of meso dialdehydes as substrates for interactions with chiral phosphonate reagents. The synthetic properties of asymmetric alkene synthesis is enhanced as a result of meso dialdehyde-chiral phosphonate interactions, termed as asymmetric Horner-Wadsworth-Emmons reactions. These reactions yield monoaddition products of desired diastereospecificities and high (E)-selectivity.

Published
1993

25. Modular asymmetric synthesis of P-chirogenic [beta]-amino phosphine boranes

Author

Johansson, Magnus J., Andersson, Kristian H.O., and Kann, Nina

Subjects
Chirality -- Analysis, Organoboron compounds -- Chemical properties, Biological sciences, Chemistry
Abstract

The enantio-enriched form of [alpha]-formyl phosphine boranes were prepared via asymmetric deprotonation of prochiral phosphine boranes or by deprotonation of PAMP.B[H.sub.3] (o-anisyl methyl phenyl phosphine). The method provides insight into a new type of P-chirogenic compounds that are highly versatile building blocks for the design and construction of new chiral phosphine ligands.

Published
2008

33. Targeting Membrane-Bound Viral RNA Synthesis Reveals Potent Inhibition of Diverse Coronaviruses Including the Middle East Respiratory Syndrome Virus

Author

Lundin, Anna, primary, Dijkman, Ronald, additional, Bergström, Tomas, additional, Kann, Nina, additional, Adamiak, Beata, additional, Hannoun, Charles, additional, Kindler, Eveline, additional, Jónsdóttir, Hulda R., additional, Muth, Doreen, additional, Kint, Joeri, additional, Forlenza, Maria, additional, Müller, Marcel A., additional, Drosten, Christian, additional, Thiel, Volker, additional, and Trybala, Edward, additional

Published
2014
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36. Asymmetric Pauson-Khand cyclization: a formal total synthesis of natural brefeldin A

Author

Bernardes, Vania, Kann, Nina, Riera, Antoni, Moyano, Albert, Pericas, Miquel A., and Greene, Andrew E.

Subjects
Organic compounds -- Synthesis, Ring formation (Chemistry) -- Analysis, Biological sciences, Chemistry
Abstract

An intermolecular asymmetric Pauson-Khand reaction can be used for the total synthesis of natural brefeldin A, a fungal metabolite. The cyclopentanone obtained as an intermediate in the Pauson-Khand reaction undergoes trans ketene acetal addition in the presence of a lithium perchlorate catalyst to form a precursor of (+)-brefeldin A.

Published
1995

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