| 1. |
- Adeyemi, Ahmed, 1986-
(författare)
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Palladium(0)-Catalyzed Synthesis of Spirocycles and Supercritical Chemistry using a Resistively Heated Flow Reactor
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This doctoral thesis focusses on an effective and selective approach to the synthesis of spirocycles using palladium(0)-catalyzed Mizoroki-Heck reactions. In addition, selective and efficient chemistry was highlighted by the design and evaluation of a novel resistively heated system for continuous flow (CF) synthesis for high-temperature and high-pressure applications.Paper I described the design and evaluation of a novel resistively heated CF system. The design of a low-cost, simple, robust, and effective CF system involving a resistively heated steel reactor capable of delivering 400 °C and 200 bar was reported. The reactor was evaluated with esterification, transesterification and direct carboxylic acid to nitrile conversions using supercritical ethanol, methanol and acetonitrile respectively. Diels-Alder reactions under neat conditions were also carried out at high temperature and pressure.Paper II reported the synthesis of spirooxindoles by a selective application of the palladium(0)-catalyzed Mizoroki-Heck spirocyclization. The precursors for the reaction were synthesized by coupling 2-iodoanilines with esters derived from enantiomerically pure (+)-Vince lactam decorated with the bulky, directing 2,5-dimethylpyrrole protecting group. Ten different spirooxindoles were reported with good yields and high regio- and stereoselectivity. Functionalization of a synthesized spirooxindole was done by a palladium(0)-catalyzed alkoxycarbonylation, followed by selective deprotections.In Paper III, ether precursors were synthesized from (+)-Vince lactam, via a Mitsunobu reaction with the corresponding iodophenols. The precursors were later subjected to conditions for intramolecular Mizoroki-Heck reaction. Overall, 12 spiroethers were synthesized in useable yields, regioselectivity up to 98% and with excellent diastereoselectivity (d.e.>98%). Further functionalization to mono-protected rigidified amino acids was also demonstrated.
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| 2. |
- Artacho Ruiz, Josep, et al.
(författare)
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On the Synthesis of Asymmetric and Dissymmetric Amino Analogues of Troger's Base
- 2009
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Ingår i: Synthesis. - : Georg Thieme Verlag KG. - 0039-7881 .- 1437-210X. ; :18, s. 3120-3126
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Tidskriftsartikel (refereegranskat)abstract
- Monoamino and diamino analogues of Troger's base have been synthesized by palladium-catalyzed aminations of the corresponding dihalo analogues using low catalyst loadings. Depending on the nature of the dihalo analogue (Br or 1). catalyst loading and the scale of the reaction, monoamino-monohalo and/or diamino analogues of Troger's base were obtained.
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| 3. |
- Artacho Ruiz, Josep, et al.
(författare)
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The synthesis and characterization of all diastereomers of a linear symmetrically fused tris-Troger's base analogue: New chiral cleft compounds
- 2006
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Ingår i: Chemistry: A European Journal. - : Wiley. - 1521-3765 .- 0947-6539. ; 12:10, s. 2692-2701
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and characterization of all diastereomers of a linear symmetrically fused tris-Troger's base analogue are described. The diastereomers are unambiguously assigned as syn-anti 1a, anti-anti 1b, and syn-syn 1c isomers, by using X-ray diffraction analysis and NMR spectroscopy. For the first time, the anti-anti and the syn-syn diastereomers of a linear symmetrically fused tris-Troger's base analogue have been synthesized. Molecules 1a and 1c are new cleft compounds and analysis of compound 1a in the solid state shows inclusion of one molecule of CH2Cl2 in the larger aromatic cleft, whereas in isomer 1c disordered solvent molecules are trapped in the extended aromatic cleft. Furthermore, in the solid state, isomer 1c forms infinite open channels along one of the crystallographic axes and perpendicular to this axis there are infinitely extending "wedged-ravines". Importantly, each of the diastereomers 1a-c is resistant to inversion at the stereogenic nitrogen atoms under strongly and weakly acidic conditions in the range from room temperature (RT) to 95 degrees C. This observed configurational stability at the stereogenic nitrogens of 1a-c is unique for analogues of Troger's base in general to date. Finally, the ratio of cleft compounds 1a and 1c significantly increased relative to cavity compound 1b when ammonium chloride was used as an additive in the Troger's base condensation to 1a-c suggesting a templating effect of the ammonium ion.
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| 4. |
- Artacho Ruiz, Josep, et al.
(författare)
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Tröger's Base Twisted Amides: Endo Functionalization and Synthesis of an Inverted Crown Ether
- 2012
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7052 .- 1523-7060. ; 14:18, s. 4706-4709
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Tidskriftsartikel (refereegranskat)abstract
- Taking advantage of the unconventional reactivity of twisted mono- and bis-amides of Tröger's base (TB), rac-6 and rac-7, respectively, the first synthesis of a 6-endo-monosubstituted TB analogue, rac-9, and the first rational synthesis of a 6,12-endo,endo-disubstituted TB analogue, rac-11, have been achieved. The bis-TB crown ether, meso-13, was prepared starting from rac-7. Meso-13 constitutes a rare example of a crown ether with an inverted methylene bridge-to-bridge bis-TB conformation both in solution and in the solid state, resulting in a reluctance to act as a receptor for cations.
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| 5. |
- Artacho Ruiz, Josep, et al.
(författare)
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Twisted Amide Analogues of Tröger's Base.
- 2012
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Ingår i: Chemistry: A European Journal. - : Wiley. - 1521-3765 .- 0947-6539. ; 18:4, s. 1038-1042
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Tidskriftsartikel (refereegranskat)abstract
- Let's do the twist: The first twisted bis-amide is obtained by the benzylic oxidation of Tröger's base (TB). Kinetic studies of its acidic hydrolysis reveal that the hydrolysis is to a large extent funneled through doubly protonated species.
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| 6. |
- Aspelin, Vidar, et al.
(författare)
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Counterintuitive Electrostatics upon Metal Ion Coordination to a Receptor with Two Homotopic Binding Sites
- 2022
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 144:7, s. 2921-2932
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Tidskriftsartikel (refereegranskat)abstract
- The consecutive binding of two potassium ions to a bis(18-crown-6) analogue of Tröger’s base (BCETB) in water was studied by isothermal titration calorimetry using four different salts, KCl, KI, KSCN, and K2SO4. A counterintuitive result was observed: the enthalpy change associated with the binding of the second ion is more negative than that of the first (ΔH°bind,2 < ΔH°bind,1). This remarkable finding is supported by continuum electrostatic theory as well as by atomic scale replica exchange molecular dynamics simulations, where the latter robustly reproduces experimental trends for all simulated salts, KCl, KI, and KSCN, using multiple force fields. While an enthalpic K+–K+attraction in water poses a small, but fundamentally important, contribution to the overall interaction, the probability of the collapsed conformation (COL) of BCETB, where both crown ether moieties (CEs) of BCETB are bent in toward the cavity, was found to increase successively upon binding of the first and second potassium ions. The promotion of the COL conformation reveals favorable intrinsic interactions between the potassium coordinated CEs, which further contribute to the observation that ΔH°bind,2 < ΔH°bind,1. While the observed trend is independent of the counterion, the origin of the significantly larger magnitude of the difference ΔH°bind,2 - ΔH°bind,1 observed experimentally for KSCN was studied in light of the weaker hydration of the thiocyanate anion, resulting in an enrichment of thiocyanate ions close to BCETB compared to the other studied counterions.
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| 7. |
- Biasin, Elisa, et al.
(författare)
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Femtosecond X-Ray Scattering Study of Ultrafast Photoinduced Structural Dynamics in Solvated[Co(terpy)2]2$
- 2016
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Ingår i: Physical Review Letters. - : American Physical Society (APS). - 1079-7114 .- 0031-9007. ; 117:1
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Tidskriftsartikel (refereegranskat)abstract
- We study the structural dynamics of photoexcited [Co(terpy)2]2+ in an aqueous solution with ultrafast x-ray diffuse scattering experiments conducted at the Linac Coherent Light Source. Through direct comparisons with density functional theory calculations, our analysis shows that the photoexcitation event leads to elongation of the Co-N bonds, followed by coherent Co-N bond length oscillations arising from the impulsive excitation of a vibrational mode dominated by the symmetrical stretch of all six Co-N bonds. This mode has a period of 0.33 ps and decays on a subpicosecond time scale. We find that the equilibrium bond-elongated structure of the high spin state is established on a single-picosecond time scale and that this state has a lifetime of ∼7 ps.
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| 8. |
- Canton, S. E., et al.
(författare)
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Watching the dynamics of electrons and atoms at work in solar energy conversion
- 2015
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Ingår i: Faraday discussions. - : Royal Society of Chemistry. - 1359-6640 .- 1364-5498. ; 185, s. 51-68
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Tidskriftsartikel (refereegranskat)abstract
- The photochemical reactions performed by transition metal complexes have been proposed as viable routes towards solar energy conversion and storage into other forms that can be conveniently used in our everyday applications. In order to develop efficient materials, it is necessary to identify, characterize and optimize the elementary steps of the entire process on the atomic scale. To this end, we have studied the photoinduced electronic and structural dynamics in two heterobimetallic ruthenium-cobalt dyads, which belong to the large family of donor-bridge-acceptor systems. Using a combination of ultrafast optical and X-ray absorption spectroscopies, we can clock the light-driven electron transfer processes with element and spin sensitivity. In addition, the changes in local structure around the two metal centers are monitored. These experiments show that the nature of the connecting bridge is decisive for controlling the forward and the backward electron transfer rates, a result supported by quantum chemistry calculations. More generally, this work illustrates how ultrafast optical and X-ray
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| 9. |
- Canton, Sophie, et al.
(författare)
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Probing the Anisotropic Distortion of Photoexcited Spin Crossover Complexes with Picosecond X-ray Absorption Spectroscopy
- 2014
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:8, s. 4536-4545
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Tidskriftsartikel (refereegranskat)abstract
- For numerous spin crossover complexes, the anisotropic distortion of the first coordination shell around the transition metal center governs the dynamics of the high-spin/low-spin interconversion. However, this structural parameter remains elusive for samples that cannot be investigated with crystallography. The present work demonstrates how picosecond X-ray absorption spectroscopy is able to capture this specific deformation in the photoinduced high-spin state of solvated [Fe(terpy)(2)](2+), a complex which belongs to the prominent family of spin crossover building blocks with nonequivalent metal-ligand bonds. The correlated changes in Fe-N-Axial, Fe-N-Distal, and bite angle N-Distal-Fe-N-Axial extracted from the measurements are in very good agreement with those predicted by DFT calculations in D-2d symmetry. The outlined methodology is generally applicable to the characterization of ultrafast nuclear rearrangements around metal centers in photoactive molecular complexes and nanomaterials, including those that do not display long-range order.
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| 10. |
- Canton, Sophie, et al.
(författare)
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Toward Highlighting the Ultrafast Electron Transfer Dynamics at the Optically Dark Sites of Photocatalysts
- 2013
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Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 4:11, s. 1972-1976
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Tidskriftsartikel (refereegranskat)abstract
- Building a detailed understanding of the structure function relationship is a crucial step in the optimization of molecular photocatalysts employed in water splitting schemes. The optically dark nature of their active sites usually prevents a complete mapping of the photoinduced dynamics. In this work, transient X-ray absorption spectroscopy highlights the electronic and geometric changes that affect such a center in a bimetallic model complex. Upon selective excitation of the ruthenium chromophore, the cobalt moiety is reduced through intramolecular electron transfer and undergoes a spin flip accompanied by an average bond elongation of 0.20 +/- 0.03 angstrom. The analysis is supported by simulations based on density functional theory structures (B3LYP*/TZVP) and FEFF 9.0 multiple scattering calculations. More generally, these results exemplify the large potential of the technique for tracking elusive intermediates that impart unique functionalities in photochemical devices.
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