Combined Photoredox and Iron Catalysis for the Cyclotrimerization of Alkynes

This is the peer reviewed version of the following article: Neumeier, M., Chakraborty, U., Schaarschmidt, D., de la Pena O'Shea, V., Perez¿Ruiz, R., & Jacobi von Wangelin, A. (2020). Combined photoredox and iron catalysis for the cyclotrimerization of alkynes. Angewandte Chemie International Edition, 59(32), 13473-13478, which has been published in final form at https://doi.org/10.1002/anie.202000907. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.[EN] Successful combinations of visible-light photocatalysis with metal catalysis have recently enabled the development of hitherto unknown chemical reactions. Dual mechanisms from merging metal-free photocatalysts and earth-abundant metal catalysts are still in their infancy. We report a photo-organo-iron-catalyzed cyclotrimerization of alkynes by photoredox activation of a ligand-free Fe catalyst. The reaction operates under very mild conditions (visible light, 20 degrees C, 1 h) with 1-2 mol % loading of the three catalysts (dye, amine, FeCl2).This work was supported by the Fonds der Chemischen Industrie (to M.N.) and the European Research Council (CoG 683150). We thank Luana Cardinale for technical support.Neumeier, M.; Chakraborty, U.; Schaarschmidt, D.; De La Pena O'shea, V.; Pérez-Ruiz, R.; Jacobi Von Wangelin, A. (2020). Combined Photoredox and Iron Catalysis for the Cyclotrimerization of Alkynes. Angewandte Chemie International Edition. 59(32):13473-13478. https://doi.org/10.1002/anie.2020009071347313478593

1H NMR spectroscopic elucidation in solution of the kinetics and thermodynamics of spin crossover for an exceptionally robust Fe2+ complex

A series of Fe2+ spin crossover (SCO) complexes [Fe(5/6)]2+ employing hexadentate ligands (5/6) with cis/trans-1,2-diamino cyclohexanes (4) as central building blocks were synthesised. The ligands were obtained by reductive amination of 4 with 2,2′-bipyridyl-6-carbaldehyde or 1,10-phenanthroline-2-carbaldehyde 3. The chelating effect and the rigid structure of the ligands 5/6 lead to exceptionally robust Fe2+ and Zn2+ complexes conserving their structure even in coordinating solvents like dmso at high temperatures. Their solution behavior was investigated using variable temperature (VT) 1H NMR spectroscopy and VT Vis spectroscopy. SCO behavior was found for all Fe2+ complexes in this series centred around and far above room temperature. For the first time we have demonstrated that the thermodynamics as well as kinetics for SCO can be deduced by using VT 1H NMR spectroscopy. An alternative scheme using a linear correction term C1 to model chemical shifts for Fe2+ SCO complexes is presented. The rate constant for the SCO of [Fe(rac-trans-5)]2+ obtained by VT 1H NMR was validated by Laser Flash Photolysis (LFP), with excellent agreement (1/(kHL + kLH) = 33.7/35.8 ns for NMR/LFP). The solvent dependence of the transition temperature T1/2 and the solvatochromism of complex [Fe(rac-trans-5)]2+ were ascribed to hydrogen bond formation of the secondary amine to the solvent. Enantiomerically pure complexes can be prepared starting with R,R- or S,S-1,2-diaminocyclohexane (R,R-trans-4 or S,S-trans-4). The high robustness of the complexes reduces a possible ligand scrambling and allows preparation of quasiracemic crystals of [Zn(R,R-5)][Fe(S,S-5)](ClO4)4·(CH3CN) composed of a 1 : 1 mixture of the Zn and Fe complexes with inverse chirality.Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich

Synthesis of 7β-hydroxy-8-ketone opioid derivatives with antagonist activity at mu- and delta-opioid receptors

Despite extensive years of research, the direct oxidation of the 7,8-double bond of opioids has so far received little attention and knowledge about the effects of this modification on activity at the different opioid receptors is scarce. We herein report that potassium permanganate supported on iron(II) sulfate heptahydrate can be used as a convenient oxidant in the one-step, heterogeneous conversion of Delta(7.8)-opioids to the corresponding 7 beta-hydroxy-8-ketones. Details of the reaction mechanism are given and the effects of the substituent at position 6 of several opioids on the reaction outcome is discussed. The opioid hydroxy ketones prepared are antagonists at the mu- and delta-opioid receptors. Docking simulations and detailed structure-activity analysis revealed that the presence of the 7 beta-hydroxy-8-ketone functionality in the prepared compounds can be used to gain activity towards the delta opioid receptor. The 7 beta-hydroxy-8-ketones prepared with this method can also be regarded as versatile intermediates for the synthesis of other opioids of interest. (C) 2018 Elsevier Masson SAS. All rights reserved.Peer reviewe

Über chirale Phosphinoferrocene und deren Anwendung in der (atropselektiven) Synthese räumlich gehinderter Biaryle über eine Suzuki-Miyaura-Reaktion

Die vorliegende Dissertation beschäftigt sich mit der Synthese und Charakterisierung drei verschiedener Typen chiraler Phosphinoferrocene sowie deren Anwendung in der Palladiumkatalysierten Suzuki-Miyaura-Reaktion. Der Schwerpunkt liegt dabei auf Untersuchungen zur Synthese räumlich gehinderter Biaryle sowie auf atropselektiven Biarylkupplungen. Über eine Ullmann-artige Kupplung von Iodferrocen mit sekundären Alkoholen wurden zunächst chirale Ferrocenylalkylether synthetisiert, die mit Hilfe dirigierter Lithiierungen in 1,1'-disubstituierte Phosphinoferrocene der Art Fe( 5-C5H4OR)( 5-C5H4-C6H4-2-PR'2) sowie planar-chirale 1,2,1'-trisubstituierte Ferrocene des Typs Fe( 5-C5H3-1-PPh2-2-OR)( 5-C5H4SiMe3) überführt werden konnten. Erstere eignen sich für die Umsetzung räumlich gehinderter Arylhalogenide in der Suzuki-Miyaura-Reaktion, wobei die katalytische Produktivität mit sinkendem Tolman Kegelwinkel der Phosphine steigt. Darüber hinaus ist es möglich, Kupplungsreaktionen zwischen nicht aktivierten Bromaromaten und Phenylboronaäure bei ultraniedriger Katalysatorbeladung (1 ppm) durchzuführen. Die 1,2-P,O-substituierten Ferrocene erlauben die Synthese tri-ortho-substituierter Biaryle. Dabei zeigte sich, dass die Enantioselektivität der Umsetzung hauptsächlich durch die planare Chiralität des Ferrocens und nicht durch den chiralen Alkoxysubstituenten bestimmt wird. Darauf aufbauend wurde eine Serie verschieden substituierter planar-chiraler Phosphinoalkenylferrocene der Art Fe( 5-C5H3-2-PR'2-(E)-CH=CHR)( 5-C5H5) synthetisiert. Die elektrochemische Untersuchung dieser Verbindungen zeigte, dass die -Donoreigenschaften des Phosphins durch die elektronischen Eigenschaften des alkenylgebundenen Substituenten R nicht verändert werden. Dies erlaubt die unabhängige Variation der -Donor-/ -Akzeptoreigenschaften des Phosphins und des Alkens. Abschließend wurde ein Vertreter der Phosphinoalkenylferrocene in der Synthese tri- und tetra-ortho-substituierter Biaryle sowie in atropselektiven Biarylkupplungen eingesetzt. Die Leistungsfähigkeit des Katalysators in der Suzuki-Miyaura-Reaktion wurde durch die Variation der Substratpalette untersucht

Crystal structure of an unknown tetrahydrofuran solvate of tetrakis(μ3-cyanato-κ3N:N:N)tetrakis[(triphenylphosphane-κP)silver(I)]

In the title compound, [{[(C6H5)3P]Ag}4{NCO}4], a distorted Ag4N4-heterocubane core is set up by four AgI ions being coordinated by the N atoms of the cyanato anions in a μ3-bridging mode. In addition, a triphenylphosphine ligand is datively bonded to each of the AgI ions. Intramolecular Ag...Ag distances as short as 3.133 (9) Å suggest the presence of argentophilic (d10...d10) interactions. Five moderate-to-weak C—H...O hydrogen-bonding interactions are observed in the crystal structure, spanning a three-dimensional network. A region of electron density was treated with the SQUEEZE procedure in PLATON [Spek (2015). Acta Cryst. C71, 9–18] following unsuccessful attempts to model it as being part of disordered tetrahydrofuran solvent molecules. The given chemical formula and other crystal data do not take into account these solvent molecules

Adaptation and perception of cloud computing in german banks

BASED ON THE RESULTS OF A MULTI-PARTICIPANT CASE STUDY THAT WAS CONDUCTED IN THE COURSE OF THE YEAR 2011, THIS ARTICLE OUTLINES THE CURRENT UTILIZATION AND ASSESSMENT OF CLOUD COMPUTING BY GERMAN BANKS

Crystal structure of cyclo-bis(μ4-2,2-diallylmalonato-κ6O1,O3:O3:O1′,O3′:O1′)tetrakis(triphenylphosphane-κP)tetrasilver(I)

In the tetranuclear molecule of the title compound, [Ag4(C9H10O4)2(C18H15P)4], the AgI ion is coordinated by one P and three O atoms in a considerably distorted tetrahedral environment. The two 2,2-diallylmalonate anions bridge four AgI ions in a μ4-(κ6O1,O3:O3:O1′,O3′:O1′) mode, setting up an Ag4O8P4 core (point group symmetry -4..) of corner-sharing tetrahedra. The shortest intramolecular Ag...Ag distance of 3.9510 (3) Å reveals that no direct d10...d10 interactions are present. Four weak intramolecular C—H...O hydrogen bonds are observed in the crystal structure of the title compound, which most likely stabilize the tetranuclear silver core

State-of-the-art IT architecture paradigms and their impact on the german financial industry

IN THE FINANCIAL INDUSTRY, INFORMATION TECHNOLOGY (IT) IS AN IMPORTANT BUSINESS ENABLER. THIS ARTICLE PRESENTS THE APPROACH AND FIRST RESULTS OF A MULTI- PARTICIPANT CASE STUDY TO DETERMINE THE STATUS QUO OF SELECTED IT ARCHITECTURE PARADIGMS AND THEIR IMPACT ON THE FINANCIAL INDUSTRY

1,4-Dihydrobenzo[g]quinoxaline-2,3-dione

The title compound, C12H8N2O2, was prepared by the reaction of the diethyl ester of naphthalenebis(oxamate) with tert-BuNH2. The molecule is nearly planar, with an r.m.s. deviation of 0.017 Å from the plane through all 16 non-H atoms. In the crystal, a three-dimensional network is formed, composed of layers of molecules along the b- and c-axis directions, due to the formation of intermolecular N—H...O hydrogen bonds, as well as of chains along the a-axis direction due to parallel displaced sandwich-type π–π interactions with average distances between the interacting molecules in the range 3.35–3.40 Å