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Catalytic enantioselective synthesis of β-amino alcohols by nitrene insertion

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Science China Chemistry 2021年第3期64卷 452-458页

作者： Zijun Zhou Yuqi Tan Xiang Shen Sergei Ivlev Eric Meggers fachbereich chemie Philipps-Universitat MarburgHans-Meerwein-Strasse 435043 MarburgGermany

Chiral β-amino alcohols are important building blocks for the synthesis of drugs, natural products, chiral auxiliaries, chiral ligands and chiral organocatalysts. The catalytic asymmetric β-amination of alcohols offers a direct strategy to access this class of molecules. Herein, we report a general intramolecular C(sp^(3))–H nitrene insertion method for the synthesis of chiral oxazolidin-2-ones as precursors of chiral β-amino alcohols. Specifically, the ring-closing C(sp^(3))–H amination of N-benzoyloxycarbamates with 2 mol% of a chiral ruthenium catalyst provides cyclic carbamates in up to 99% yield and with up to 99% *** method is applicable to benzylic, allylic, and propargylic C–H bonds and can even be applied to completely non-activated C(sp^(3))–H bonds, although with somewhat reduced yields and stereoselectivities. The obtained cyclic carbamates can subsequently be hydrolyzed to obtain chiral β-amino alcohols. The method is very practical as the catalyst can be easily synthesized on a gram scale and can be recycled after the reaction for further use. The synthetic value of the new method is demonstrated with the asymmetric synthesis of a chiral oxazolidin-2-one as intermediate for the synthesis of the natural product aurantioclavine and chiral β-amino alcohols that are intermediates for the synthesis of chiral amino acids, indane-derived chiral Box-ligands, and the natural products dihydrohamacanthin A and dragmacidin A.

关键词： asymmetric catalysis nitrene amination chiral-at-metal ruthenium

Enantioselective and Enantioconvergent Iron-Catalyzed C(sp^(3))-H Aminations to Chiral 2-Imidazolidinones

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Chinese Journal of Chemistry 2023年第17期41卷 2065-2070页

作者： Tianjiao Cui Chen-Xi Ye Jordan Thelemann Daniel Jenisch Eric Meggers fachbereich chemie Philipps-Universitat MarburgHans-Meerwein-Strasse 435043MarburgGermany

Comprehensive Summary Enantioselective or enantioconvergent iron-catalyzed ring-closing C(sp^(3))-H aminations of N-aroyloxyurea through intermediate iron nitrene species provide chiral 2-imidazolidinones in up to 99%yield and with up to 95%ee(40 examples).This is a rare example in which sustainable iron catalysis is combined with C(sp^(3))-H amination and asymmetric catalysis.

关键词： Iron Asymmetric catalysis C-H activation Amination Nitrenes Heterocycles

Cluster Chemistry with(Pseudo-)Tetrahedra Involving Group 13-15(Semi-)Metal Atoms

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CCS Chemistry 2022年第3期4卷 809-824页

作者： Fuxing Pan Lukas Guggolz Stefanie Dehnen fachbereich chemie and Wissenschaftliches Zentrum für Materialwissenschaften Philipps-Universität Marburg35043 Marburg

Compounds containing(pseudo-)tetrahedral main group(semi-)metal units are fundamentally important in three ***,they provide new strategies for the stabilization of tetrahedral units,such as Pn_(4)(Pn=P,As)and their isoelectronic analogs,in the coordination sphere of d-/f-block metal ***,they serve as first-step models for the activation of tetrahedral ***,they are starting materials for subsequent transformations toward larger clusters or *** or full isoelectronic replacement of the pnictogen atoms in P4 or As_(4) results in a variety of(pseudo-)tetrahedral anions,Tt_(4)^(4−)(Tt=Si,Ge,Sn,Si/Ge),(Ge_(3)Pn)^(3−)(Pn=P,As;formed in situ),(Tt_(2)Pn_(2))^(2−)(Tt/Pn=Ge/P,Ge/As,Sn/Sb,Sn/Bi,Pb/Sb,Pb/Bi),or(TrBi_(3))^(2−)(Tr=Ga,In,Tl),and also cations,(P3Ch)+(Ch=S,Se,Te).The anions have proven to be excellent starting materials and building blocks for multinary clusters in the context of Zintl *** compounds,which push forward the boundary of intriguing P4 chemistry,have never been thoroughly summarized *** this minireview,we introduce all known intact(pseudo-)tetrahedral group 13–15 units,as well as the coordination compounds based on them,along with two new missing links,[Au(η^(2-)Tt_(2)Bi_(2))_(2)]^(3−)(Tt=Sn,Pb).

关键词： tetrahedra coordination compounds group 13-15(semi-)metals Zintl anions gold

Yb-and Er concentration dependence of the upconversion luminescence of highly doped NaYF_(4):Yb,Er/NaYF_(4):Lu core/shell nanocrystals prepared by a water-free synthesis

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Nano Research 2022年第10期15卷 9639-9646页

作者： Christian Würth Bettina Grauel Monika Pons Florian Frenzel Philipp Rissiek Kerstin Rücker Markus Haase Ute Resch-Genger Federal Institute for Materials Research and Testing(BAM) Division BiophotonicsRichard-Willstaetter-Str.1112489 BerlinGermany Institut für chemie Neuer Materialien Fachbereich Biologie/ChemieUniversität OsnabrückBarbarastraße 749076 OsnabrückGermany

High sensitizer and activator concentrations have been increasingly examined to improve the performance of multi-color emissive upconversion(UC)nanocrystals(UCNC)like NaYF_(4):Yb,Er and first strategies were reported to reduce concentration quenching in highly doped *** luminescence(UCL)is,however,controlled not only by dopant concentration,yet by an interplay of different parameters including size,crystal and shell quality,and excitation power density(P).Thus,identifying optimum dopant concentrations requires systematic studies of UCNC designed to minimize additional quenching pathways and quantitative ***,we quantify the dopant concentration dependence of the UCL quantum yield(ΦUC)of solid NaYF_(4):Yb,Er/NaYF_(4):Lu upconversion core/shell nanocrystals of varying Yb3+and Er3+concentrations(Yb3+series:20%‒98%Yb3+;2%Er3+;Er3+series:60%Yb3+;2%‒40%Er3+).To circumvent other luminescence quenching processes,an elaborate synthesis yielding OH-free UCNC with recordΦUC of~9%and~25 nm core particles with a thick surface shell were *** Yb3+concentrations barely reduceΦUC from~9%(20%Yb3+)to~7%(98%Yb3+)for an Er3+concentration of 2%,thereby allowing to strongly increase the particle absorption cross section and UCNC *** an increased Er3+concentration reducesΦUC from~7%(2%Er3+)to 1%(40%)for 60%Yb3+.Nevertheless,at very high P(>1 MW/cm^(2))used for microscopic studies,highly Er3+-doped UCNC display a high brightness because of reduced *** findings underline the importance of synthesis control and will pave the road to many fundamental studies of UC materials.

关键词： highly doped upconversion nanocrystals core/shell nanoparticles upconversion luminescence efficiency NaYF_(4):Yb Er concentration quenching

Potential Correlations between Unexplained Experimental Observables and Hot Projectile-Like Fragments in Primary Interactions above ECM/u≈ 150 MeV

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World Journal of Nuclear Science and Technology 2013年第4期3卷 155-161页

作者： Eberhard Ganssauge Wolfram Westmeier Reinhard Brandt fachbereich chemie Philipps-University Marburg Germany fachbereich chemie Philipps-University Marburg Germany Dr. Westmeier GmbH Ebsdorfergrund Germany fachbereich Physik Philipps University Marburg Germany

An enhanced neutron production and an enhanced nuclear destruction due to secondary fragments have been observed in very thick targets irradiated with high energy ions. This enhancement is beyond theoretical calculations and it is an unresolved problem. It is observed only when primary ion interactions exceed an energy threshold (ECM/u ≈ 150 MeV). Investigations using nuclear emulsions for very high-energy nuclear reactions suggest that two distinctly different classes of relativistic projectile-like fragments are emitted in primary interactions: a “cool” channel with a temperature of (T(p)cool ≈ 10 MeV), and a “hot” channel with (T(p)hot ≈ 40 MeV. This second reaction class may induce the above mentioned enhanced reactions of secondary fragments, thus being responsible for unresolved problems. This assumption should be studied in further experiments. Nuclear interactions of secondary particles in thick targets are of interest, in particular in view of radiation protection needs for high energy and high intensity heavy ion accelerators. Many basic ideas of this paper go back to the late Professor E. Schopper (Frankfurt).

关键词： Very High Energy Projectile Hot Projectile Fragments Cool Target Fragments Unresolved Problems

Quenchants for Induction Hardening for the Automotive Industry, Choice and Maintenance

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材料热处理学报 2004年第5期25卷 514-518页

作者： Hartmut Beitz Thorsten Beitz PETROFER chemie Headquarters Hildesheim GermanyPETROFER CHEMIE Department of Heat Treatment Hildesheim Germany

The different types of quenchants for induction hardening - mainly for shower quenching - but also for immersion will be described in regard to their properties, film-formation, remaining residues, how to handle these etc.. Furtheron the maintenance of such quench fluids will be desribed in detail regarding concentration control, control of growth of micro-organism, contamination and maintenance.

关键词：感应淬火淬火剂绝缘薄膜热处理

Multi-scale simulations of apatite-collagen composites： from molecules to materials

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Frontiers of Materials Science 2017年第1期11卷 1-12页

作者： Dirk ZAHN Lehrstuhl for Theoretische chemie/Computer chemie Centrum Friedrich-Alexander Universitat Erlangen-Numberg Nagelsbachstraβe25 91052 Erlangen Germany

We review scale-bridging simulation studies for the exploration of atomic- to-meso scale processes that account for the unique structure and mechanic properties of apatite-protein composites. As the atomic structure and composition of such complex biocomposites only partially is known, the first part （i） of our modelling studies is dedicated to realistic crystal nucleation scenarios of inorganic-organic composites. Starting from the association of single ions, recent insights range from the mechanisms of motif formation, ripening reactions and the self-organization of nanocrystals, including their interplay with growth-controlling molecular moieties. On this basis, （ii） reliable building rules for unprejudiced scale-up models can be derived to model bulk materials. This is exemplified for （enamel-like） apatite-protein composites, encompassing up to 106 atom models to provide a realistic account of the 10 nm length scale, whilst model coarsening is used to reach pm length scales. On this basis, a series of deformation and fracture simulation studies were performed and helped to rationalize biocomposite hardness, plasticity, toughness, self-healing and fracture mechanisms. Complementing experimental work, these modelling studies provide particularly detailed insights into the relation of hierarchical composite structure and favorable mechanical properties.

关键词： biocomposites deformation fracture molecular simulation

Structure and bonding of donor-acceptor complexes XBeY（X=CO, OC, Ng;Y=O, CO3）

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Structure and bonding of donor-acceptor complexes XBeY（X=CO...

Regulation of cytochrome c oxidase contributes to health and optimal life

中国化学会第29届学术年会

作者： Qingnan Zhang MH Chen MF Zhou G Frenking Department of Chemistry Fudan University fachbereich chemie Philipps-Universit?t

Reactions of laser-evaporated beryllium atoms with CO2 molecules formed OCBeO and OCBeCO3 complexes in solid neon,which rearranged to COBeO and COBeCO3 isomers under UV light *** C-O stretching frequency of OCBeCO3 was observed at 2263.1 cm-1,which is significantly higher than that of OCBeO at *** chemical calculations reveal that the binding energy of OCBeO is larger than that of *** observed unusually high frequency of OCBeCO3 is due to strong electrostatic but weakπback-donation interaction between CO and *** NgBeCO3（Ng=Ar,Kr,Xe）complexes were also prepared by reactions of beryllium atoms with CO and O2 mixtures in solid neon matrix doped by heavier noble gas *** calculations suggest that these complexes involve strong noble gas bonding which is dominated by polarization and charge transfer interactions.

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World Journal of Biological Chemistry 2020年第2期11卷 52-61页

作者： Bernhard Kadenbach Department of Chemistry/Biochemistry Fachbereich ChemiePhilipps-Universität MarburgMarburg D-35043HessenGermany

The generation of cellular energy in the form of ATP occurs mainly in mitochondria by oxidative *** c oxidase(CytOx),the oxygen accepting and rate-limiting step of the respiratory chain,regulates the supply of variable ATP demands in cells by“allosteric ATP-inhibition of CytOx.”This mechanism is based on inhibition of oxygen uptake of CytOx at high ATP/ADP ratios and low ferrocytochrome c concentrations in the mitochondrial matrix via cooperative interaction of the two substrate binding sites in dimeric *** mechanism keeps mitochondrial membrane potentialΔΨm and reactive oxygen species(ROS)formation at low healthy *** signals increase cytosolic calcium leading to Ca^2+-dependent dephosphorylation of CytOx subunit I at the cytosolic side accompanied by switching off the allosteric ATPinhibition and monomerization of *** is followed by increase ofΔΨm and formation of ROS.A hypothesis is presented suggesting a dynamic change of binding of NDUFA4,originally identified as a subunit of complex I,between monomeric CytOx(active state with highΔΨm,high ROS and low efficiency)and complex I(resting state with lowΔΨm,low ROS and high efficiency).

关键词： Cytochrome c oxidase Regulation of respiration Allosteric ATP-inhibition NDUFA4 Reversible phosphorylation Efficiency of ATP synthesis Dimerization of cytochrome c oxidase