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81.
Philipp Rotering Lukas F. B. Wilm Janina A. Werra Dr. Fabian Dielmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(2):406-411
Electron-rich tertiary phosphines are valuable species in chemical synthesis. However, their broad application as ligands in catalysis and reagents in stoichiometric reactions is often limited by their costly synthesis. Herein, we report the synthesis and properties of a series of phosphines with 1-alkylpyridin-4-ylidenamino and 1-alkylpyridin-2-ylidenamino substituents that are accessible in a very short and scalable route starting from commercially available aminopyridines and chlorophosphines. The determination of the Tolman electronic parameter (TEP) value reveals that the electron donor ability can be tuned by the substituent pattern at the aminopyridine backbone and it can exceed that of common alkylphosphines and N-heterocyclic carbenes. The potential of the new phosphines as strong nucleophiles in phosphine-mediated transformations is demonstrated by the formation of Lewis base adducts with CO2 and CS2. In addition, the coordination chemistry of the new phosphines towards CuI, AuI, and PdII metal centers has been explored, and a convenient procedure to introduce the most basic phosphine into metal complexes starting from air-stable phosphonium salt is described. 相似文献
82.
Martin Piesch Dr. Fabian Dielmann Stephan Reichl Prof. Dr. Manfred Scheer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(7):1518-1524
A systematic study on the reactivity of the triple-decker complex [(Cp’’’Co)2(μ,η4:η4-C7H8)] ( A ) (Cp’’’=1,2,4-tritertbutyl-cyclopentadienyl) towards sandwich complexes containing cyclo-P3, cyclo-P4, and cyclo-P5 ligands under mild conditions is presented. The heterobimetallic triple-decker sandwich complexes [(Cp*Fe)(Cp’’’Co)(μ,η5:η4-P5)] ( 1 ) and [(Cp’’’Co)(Cp’’’Ni)(μ,η3:η3-P3)] ( 3 ) (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) were synthesized and fully characterized. In solution, these complexes exhibit a unique fluxional behavior, which was investigated by variable temperature NMR spectroscopy. The dynamic processes can be blocked by coordination to {W(CO)5} fragments, leading to the complexes [(Cp*Fe)(Cp’’’Co)(μ3,η5:η4:η1-P5){W(CO)5}] ( 2 a ), [(Cp*Fe)(Cp’’’Co)(μ4,η5:η4:η1:η1-P5){(W(CO)5)2}] ( 2 b ), and [(Cp’’’Co)(Cp’’’Ni)(μ3,η3:η2:η1-P3){W(CO)5}] ( 4 ), respectively. The thermolysis of 3 leads to the tetrahedrane complex [(Cp’’’Ni)2(μ,η2:η2-P2)] ( 5 ). All compounds were fully characterized using single-crystal X-ray structure analysis, NMR spectroscopy, mass spectrometry, and elemental analysis. 相似文献
83.
Leiming Zhu Leonard Himmel Jean Michél Merkes Prof. Dr. Fabian Kiessling Prof. Dr. Magnus Rueping Dr. Srinivas Banala 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(19):4232-4235
Atropisomerism has been observed in a variety of biaryl compounds and meso-aryl substituted porphyrins. However, in porphyrins, this phenomenon had been shown only with o-substituted 6-membered aromatic groups at the meso-position. We show herein that a 5-membered heteroaromatic (N-mesyl-pyrrol-2-yl) group at the meso-position leads to atropisomerism. In addition, we report a ‘one-pot’ synthetic route for the synthesis of ‘all-pyrrolic’ porphyrin (APP) with several N-protection groups (Boc, Cbz, Ms and Ts). Among these groups, we found that only the Ms group gave four individually separable atropisomers of meso-tetra(N-Ms-pyrrol-2-yl) porphyrin. Furthermore, the reductive removal of Cbz- was achieved to obtain meso-tetra(pyrrol-2-yl) porphyrin. Thus, our synthetic procedure provides an easy access to a group of APPs and stable atropisomers, which is expected to expand the application of novel APP-based materials. 相似文献
84.
Alexander V. Fejzagić Sebastian Myllek Fabian Hogenkamp Julian Greb Prof. Dr. Jörg Pietruszka Dr. Thomas Classen 《ChemistryOpen》2020,9(9):959-966
Screening for an interesting biocatalyst and its subsequent kinetic characterization depends on a reliable activity assay. In this work, a fluorometric assay based on the halogenation of 4-methyl-7-diethylamino-coumarin was established to monitor haloperoxidase-activity. Since haloperoxidases utilize hydrogen peroxide and halide ions to halogenate a broad range of substrates by releasing hypohalous acids, a direct quantification of haloperoxidase-activity remains difficult. With the system presented here, 3-bromo-4-methyl-7-diethylaminocoumarin is preferentially formed and monitored by fluorescence measurements. As starting material and product share similar spectroscopical properties, a two-dimensional calibration ap-proach was utilized to allow for quantification of each compound within a single measurement. To validate the system, the two-dimensional Michaelis-Menten kinetics of a vanadium-dependent chloroperoxidase from Curvularia inaequalis were recorded, yielding the first overall kinetic parameters for this enzyme. With limits of detection and quantification in the low μm range, this assay may provide a reliable alternative system for the quantification of haloperoxidase-activity. 相似文献
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Fabian WM 《The Journal of organic chemistry》2002,67(21):7475-7482
The site of nucleophilic addition to five-membered heterocyclic 2,3-diones (4-iminomethylfuran-2,3-dione A1 and 4-formyl-pyrrole-2,3-dione B1) is studied by density functional theory calculations (B3LYP/6-31G) with water as the nucleophile. Both uncatalyzed and water-assisted 1,2-addition to the lactone (lactam) and the keto carbonyl group, and conjugate addition to C5 of the heterocycle and the heteroatom of the 4-iminomethyl (formyl) moiety are considered. In addition, concerted and stepwise ring fission of the lactone (lactam) ring is also treated. The effect of solvation (aqueous solution) is taken into account by the polarizable continuum model (PCM) and the Poisson-Boltzmann SCRF method (PB-SCRF), as well as explicit water molecules. Only this latter approach yields meaningful activation free energies. Barriers for addition of H2O increase in the order 1,4-addition to C5 < addition to the lactone (lactam) carbonyl < hydration of the 3-keto group. No reaction path for concerted water-assisted ring opening could be found. 相似文献
90.
We consider a one-dimensional charge density wave insulator formed by umklapp processes in a quarter-filled band. The spectrum of the model consists of gapless, uncharged excitations carrying spin +/- 1/2 (spinons) and gapped, spinless excitations carrying charge -/+ signe/2 (solitons and antisolitons). We calculate the low-energy behavior of the single-electron Green's function at zero temperature. The spectral function exhibits a featureless scattering continuum of two solitons and many spinons. The theory predicts that the gap observed by angle resolved photoemission is twice the activation gap in the dc conductivity. We comment on possible applications to PrBa(2)Cu(3)O(7) and to the Bechgaard salts. 相似文献