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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Dutta, Subhajit, et al.
(författare)
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Three-in-One C2H2-Selectivity-Guided Adsorptive Separation across an Isoreticular Family of Cationic Square-Lattice MOFs
- 2021
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Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773.
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Tidskriftsartikel (refereegranskat)abstract
- Energy-efficient selective physisorption driven C2H2 separation from industrial C2-C1 impurities such as C2H4, CO2 and CH4 is of great importance in the purification of downstream commodity chemicals. We address this challenge employing a series of isoreticular cationic metal-organic frameworks, namely iMOF-nC (n=5, 6, 7). All three square lattice topology MOFs registered higher C2H2 uptakes versus the competing C2-C1 gases (C2H4, CO2 and CH4). Dynamic column breakthrough experiments on the best-performing iMOF-6C revealed the first three-in-one C2H2 adsorption selectivity guided separation of C2H2 from 1:1 C2H2/CO2, C2H2/C2H4 and C2H2/CH4 mixtures. Density functional theory calculations critically examined the C2H2 selective interactions in iMOF-6C. Thanks to the abundance of square lattice topology MOFs, this study introduces a crystal engineering blueprint for designing C2H2-selective layered metal-organic physisorbents, previously unreported in cationic frameworks.
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| 3. |
- Mai, Juri, 1987-, et al.
(författare)
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Z‑selective alkene formation from reductive aldehyde homo-couplings
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Current methodologies for the direct coupling of two aldehydes to alkenes afford almost exclusively the thermodynamically favoured E-isomer. Our recent efforts to find phosphorus-based reagent as replacements for the low-valent Ti species used in McMurry couplings offers a possibility to change this shortcoming, and to design new reagents that allow for the formation of high proportions of Z-alkenes under kinetic control. Here, we report on the first such reagent, a phosphanyl phosphonate MesFP(H)P(O)(OEt)2 with an electron-deficient MesF = 2,4,6-(CF3)3Ph substituent. The reagent promotes the reductive homo-coupling of (hetero)aromatic aldehydes to alkenes with high Z-selectivity. The one-pot procedure passes through phosphaalkene intermediates, the 31P NMR chical shifts of which correlate with the proportion of formed Z-isomer, with the most deshielded phosphaalkenes giving more than 90% steroselectivity of the Z-alkene.
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| 4. |
- Slanina, Tomáš, et al.
(författare)
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Impact of Excited-State Antiaromaticity Relief in a Fundamental Benzene Photoreaction Leading to Substituted Bicyclo[3.1.0]hexenes
- 2020
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society. - 0002-7863 .- 1520-5126. ; 142:25, s. 10942-10954
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Tidskriftsartikel (refereegranskat)abstract
- Benzene exhibits a rich photochemistry which can provide access to complex molecular scaffolds that are difficult to access with reactions in the electronic ground state. While benzene is aromatic in its ground state, it is antiaromatic in its lowest ππ∗ excited states. Herein, we clarify to what extent relief of excited-state antiaromaticity (ESAA) triggers a fundamental benzene photoreaction: the photoinitiated nucleophilic addition of solvent to benzene in acidic media leading to substituted bicyclo[3.1.0]hex-2-enes. The reaction scope was probed experimentally, and it was found that silyl-substituted benzenes provide the most rapid access to bicyclo[3.1.0]hexene derivatives, formed as single isomers with three stereogenic centers in yields up to 75% in one step. Two major mechanism hypotheses, both involving ESAA relief, were explored through quantum chemical calculations and experiments. The first mechanism involves protonation of excited-state benzene and subsequent rearrangement to bicyclo[3.1.0]hexenium cation, trapped by a nucleophile, while the second involves photorearrangement of benzene to benzvalene followed by protonation and nucleophilic addition. Our studies reveal that the second mechanism is operative. We also clarify that similar ESAA relief leads to puckering of S1-state silabenzene and pyridinium ion, where the photorearrangement of the latter is of established synthetic utility. Finally, we identified causes for the limitations of the reaction, information that should be valuable in explorations of similar photoreactions. Taken together, we reveal how the ESAA in benzene and 6π-electron heterocycles trigger photochemical distortions that provide access to complex three-dimensional molecular scaffolds from simple reactants.
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