| 1. |
- Goesten, Maarten, et al.
(författare)
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Cesium's off-the-map valence orbital
- 2017
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Ingår i: Angewandte Chemie. - : Wiley. - 1521-3773 .- 1433-7851 .- 0044-8249 .- 1521-3757.
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Tidskriftsartikel (refereegranskat)abstract
- The Td-symmetric [CsO4]+ ion, featuring Cs in an oxidation state of 9, is computed to be a minimum. Cs uses outer core 5s and 5p orbitals to bind the oxygens. The valence Cs 6s orbital lies too high to be involved in bonding, and contributes to Rydberg levels only. From a Molecular Orbital perspective, the bonding scheme reminds of XeO4: an octet of electrons to bind electronegative ligands, and no low-lying acceptor orbitals on the central atom. In this sense, Cs+ resembles hypervalent Xe.
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| 2. |
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| 3. |
- Akkarasamiyo, Sunisa, et al.
(författare)
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Intermolecular Stereospecific Substitution of Underivatized Enantioenriched Secondary Alcohols by Organocatalysis
- 2019
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 58:50, s. 17908-17910
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Tidskriftsartikel (refereegranskat)abstract
- The stereospecific substitution of non-derivatized and non-allylic enantioenriched alcohols with only water as a by-product would enable the use of readily available alcohols as substrates for green and sustainable transformations. However, the poor leaving group ability of the OH group has hampered the development of such a process. Denton and co-workers recently described the use of (2-hydroxybenzyl)diphenylphosphine oxide as a catalyst of a redox-neutral and zero-waste-generating Mitsunobu reaction. This innovative process constitutes the first intermolecular stereospecific substitution of non-allylic alcohols, and might find industrial applications.
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| 4. |
- Alam, Rauful, et al.
(författare)
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Catalytic Asymmetric Allylboration of Indoles and Dihydroisoquinolines with Allylboronic Acids : Stereodivergent Synthesis of up to Three Contiguous Stereocenters
- 2016
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 55:46, s. 14417-14421
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Tidskriftsartikel (refereegranskat)abstract
- The catalytic asymmetric allylboration of cyclic imines with gamma,gamma-disubstituted allylboronic acids provides products with adjacent stereocenters in high yield and stereoselectivity. Various electrophiles, including 3,4-dihydroisoquinolines and indoles, were prenylated in a fully stereodivergent fashion by switching the E/Z geometry of the allylboronate and/or the enantiomer of the BINOL catalyst. 3-Methylindole provided products with three adjacent stereocenters with high stereoselectivity in one synthetic operation.
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| 5. |
- Andersen, Thomas L., et al.
(författare)
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Application of Methyl Bisphosphine-Ligated Palladium Complexes for Low Pressure N-C-11-Acetylation of Peptides
- 2017
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 56:16, s. 4549-4553
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Tidskriftsartikel (refereegranskat)abstract
- A mild and effective method is described for C-11-labeling of peptides selectively at the N-terminal nitrogen or at internal lysine positions. The presented method relies on the use of specific biphosphine palladium-methyl complexes and their high reactivity towards amino-carbonylation of amine groups in the presence [C-11] carbon monoxide. The protocol facilitates the production of native N-C-11-acetylated peptides, without any structural modifications and has been applied to a selection of bioactive peptides.
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| 6. |
- Bae, Juna, et al.
(författare)
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Phase Transformation Behavior of a Two-Dimensional Zeolite
- 2019
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 58:30, s. 10230-10235
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the molecular-level mechanisms of phase transformation in solids is of fundamental interest for functional materials such as zeolites. Two-dimensional (2D) zeolites, when used as shape-selective catalysts, can offer improved access to the catalytically active sites and a shortened diffusion length in comparison with their 3D analogues. However, few materials are known to maintain both their intralayer microporosity and structure during calcination for organic structure-directing agent (SDA) removal. Herein we report that PST-9, a new 2D zeolite which has been synthesized via the multiple inorganic cation approach and fulfills the requirements for true layered zeolites, can be transformed into the small-pore zeolite EU-12 under its crystallization conditions through the single-layer folding process, but not through the traditional dissolution/recrystallization route. We also show that zeolite crystal growth pathway can differ according to the type of organic SDAs employed.
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| 7. |
- Bai, Licheng, et al.
(författare)
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Explaining the Size Dependence in Platinum-Nanoparticle-Catalyzed Hydrogenation Reactions
- 2016
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 55:50, s. 15656-15661
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogenation reactions are industrially important reactions that typically require unfavorably high H-2 pressure and temperature for many functional groups. Herein we reveal surprisingly strong size-dependent activity of Pt nanoparticles (PtNPs) in catalyzing this reaction. Based on unambiguous spectral analyses, the size effect has been rationalized by the size-dependent d-band electron structure of the PtNPs. This understanding enables production of a catalyst with size of 1.2 nm, which shows a sixfold increase in turnover frequency and 28-fold increase in mass activity in the regioselective hydrogenation of quinoline, compared with PtNPs of 5.3 nm, allowing the reaction to proceed under ambient conditions with unprecedentedly high reaction rates. The size effect and the synthesis strategy developed herein may provide a general methodology in the design of metal-nanoparticle-based catalysts for a broad range of organic syntheses.
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| 8. |
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| 9. |
- Belanger-Chabot, Guillaume, et al.
(författare)
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Ammonia-(Dinitramido)boranes: High-Energy-Density Materials.
- 2015
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Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 54, s. 11730-11734
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Tidskriftsartikel (refereegranskat)abstract
- Two ammonia-(dinitramido)boranes were synthesized by the reaction of dinitroamine with ammonia-borane. These compds. are the first reported examples of (dinitramido)boranes. Ammonia-mono(dinitramido)borane is a perfectly oxygen-balanced high-energy-d. material (HEDM) composed of an ammonia-BH2 fuel group and a strongly oxidizing dinitramido ligand. Although it is thermally not stable enough for practical applications, its predicted specific impulse as a solid rocket propellant would be 333 s. Its predicted performance as an explosive matches that of pentaerythtritol tetranitrate (PETN) and significantly exceeds that of trinitrotoluene (TNT). Its structure was established by X-ray crystallog. and vibrational and multinuclear NMR spectroscopy. Addnl., the over-oxidized ammoniabis(dinitramido)borane was detected by NMR spectroscopy. [on SciFinder(R)]
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| 10. |
- Belanger-Chabot, Guillaume, et al.
(författare)
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Dinitramidoborates, a Fascinating Case of Competing Oxygen and Nitrogen Donors and Tautomerism
- 2017
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Ingår i: Angewandte Chemie. - : Wiley. - 1521-3773 .- 1433-7851. ; 56:36, s. 10881-10885
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Tidskriftsartikel (refereegranskat)abstract
- Reactions of the BH4- anion with equimolar amounts of HN(NO2)2 or of BH3*THF with K+[N(NO2)2]- produced a mono-substituted [BH3N(NO2)2]- anion which contains a B-N connected dinitramido ligand. The reaction of BH4- with two equivalents of HN(NO2)2 afforded the di-substituted borate anion consisting of two isomers, one with both nitramido ligands attached to B through N and the other one with one ligand attached through N and the other one through O. The disubstituted dinitramidoborates are marginally stable under ambient conditions, and the isomer with two N-connected ligands was characterized by its crystal structure. A tri-substituted borate was tentatively identified by NMR in the reaction of BH4- with a large excess of HN(NO2)2. All anions are highly energetic. Theoretical calculations show that the energy differences between the B-N and B-O tautomers are small, explaining the observed ease of ligand exchange.
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