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11.
Eleni Georgiou Davide Spinnato Kang Chen Paolo Melchiorre Kilian Muiz 《Chemical science》2022,13(27):8060
We report a photocatalytic strategy for the chemodivergent radical benzylation of 4-cyanopyridines. The chemistry uses a single photoredox catalyst to generate benzyl radicals upon N–F bond activation of 2-alkyl N-fluorobenzamides. The judicious choice of different photocatalyst quenchers allowed us to select at will between mechanistically divergent processes. The two reaction manifolds, an ipso-substitution path proceeding via radical coupling and a Minisci-type addition, enabled selective access to regioisomeric C4 or C2 benzylated pyridines, respectively. Mechanistic investigations shed light on the origin of the chemoselectivity switch.We report a photocatalytic strategy for the chemodivergent radical benzylation of 4-cyanopyridines. The chemistry uses a single photoredox catalyst to generate benzyl radicals upon N–F bond activation of 2-alkyl N-fluorobenzamides. 相似文献
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Brodowski W Bilger R Calén H Clement H Ekström C Fransson K Greiff J Häggström S Höistad B Johanson J Johansson A Johansson T Kilian K Kullander S Kupść A Marciniewski P Morosov B Oelert W Pätzold J Ruber RJ Schepkin M Scobel W Seluzhenkov I Stepaniak J Sukhanov A Turowiecki A Wagner GJ Wilhelmi Z Zabierowski J Zlomanczuk J 《Physical review letters》2002,88(19):192301
The pp-->pp pi(+) pi(-) reaction has been measured exclusively near threshold at CELSIUS. The total cross sections are nearly an order of magnitude lower than expected from previous inclusive measurements. The differential cross sections reveal pp-->pp(*)(1440)-->pp sigma = pp(pi(+)pi(-))(I = l = 0) as the dominant process as well as significant contributions from p(*)-->Delta(++)pi(-)-->psigma. The observed anisotropy in the proton angular dependence is consistent with heavy-meson exchange. In the invariant mass spectra, no narrow structures of statistical relevance (3sigma) are found. 相似文献
14.
Philip M. Keil Ademola Soyemi Kilian Weisser Prof. Tibor Szilvási Prof. Christian Limberg Dr. Terrance J. Hadlington 《Angewandte Chemie (International ed. in English)》2023,62(19):e202381961
The open-shell cationic stannylene-iron(0) complex 4 ( 4 =[PhiPDippSn⋅Fe⋅IPr]+; PhiPDipp={[Ph2PCH2Si(iPr)2](Dipp)N}; Dipp=2,6-iPr2C6H3; IPr=[(Dipp)NC(H)]2C:) cooperatively and reversibly cleaves dihydrogen at the Sn−Fe interface under mild conditions (1.5 bar, 298 K), in forming bridging hydrido-complex 6 . The One-electron oreduction of the related GeII−Fe0 complex 3 leads to oxidative addition of one C−P linkage of the PhiPDipp ligand in an intermediary Fe−I complex, leading to FeI phosphide species 7 . One-electron reduction reaction of 4 gives access to the iron(−I) ferrato-stannylene, 8 , giving evidence for the transient formation of such a species in the reduction of 3 . The covalently bound tin(II)-iron(−I) compound 8 has been characterised through EPR spectroscopy, SQUID magnetometry, and supporting computational analysis, which strongly indicate a high localization of electron spin density at Fe−I in this unique d9-iron complex. 相似文献
15.
Libo Li Ken A. Dill Christopher J. Fennell 《Journal of computer-aided molecular design》2014,28(3):259-264
Here, we test a method, called semi-explicit assembly (SEA), that computes the solvation free energies of molecules in water in the SAMPL4 blind test challenge. SEA was developed with the intention of being as accurate as explicit-solvent models, but much faster to compute. It is accurate because it uses pre-simulations of simple spheres in explicit solvent to obtain structural and thermodynamic quantities, and it is fast because it parses solute free energies into regionally additive quantities. SAMPL4 provided us the opportunity to make new tests of SEA. Our tests here lead us to the following conclusions: (1) The newest version, called Field-SEA, which gives improved predictions for highly charged ions, is shown here to perform as well as the earlier versions (dipolar and quadrupolar SEA) on this broad blind SAMPL4 test set. (2) We find that both the past and present SEA models give solvation free energies that are as accurate as TIP3P. (3) Using a new approach for force field parameter optimization, we developed improved hydroxyl parameters that ensure consistency with neat-solvent dielectric constants, and found that they led to improved solvation free energies for hydroxyl-containing compounds in SAMPL4. We also learned that these hydroxyl parameters are not just fixing solvent exposed oxygens in a general sense, and therefore do not improve predictions for carbonyl or carboxylic-acid groups. Other such functional groups will need their own independent optimizations for potential improvements. Overall, these tests in SAMPL4 indicate that SEA is an accurate, general and fast new approach to computing solvation free energies. 相似文献
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The COSY-TOF Collaboration F. Hauenstein E. Borodina H. Clement E. Doroshkevich R. Dzhygadlo K. Ehrhardt W. Eyrich W. Gast A. Gillitzer D. Grzonka S. Jowzaee P. Klaja L. Kober K. Kilian M. Krapp M. Mertens P. Moskal J. Ritman E. Roderburg M. Röder W. Schroeder T. Sefzick J. Smyrski P. Wintz P. Wüstner 《The European Physical Journal A - Hadrons and Nuclei》2016,52(11):337
18.
Bolm C Hildebrand JP Muñiz K Hermanns N 《Angewandte Chemie (International ed. in English)》2001,40(18):3284-3308
Addition and substitution reactions with carbon nucleophiles are fundamental processes in organic synthesis, and the development of general catalytic asymmetric variants thereof is still a major challenge today. In contrast to enantioselective alkyl transfer reactions, the corresponding arylations have not yet reached a high level of maturity. The existing protocols are either of no general applicability or are limited in terms of selectivity. This article summarizes established routes for catalytic asymmetric aryl transfer together with the latest developments in this area. The scope and limitations of this reaction are discussed. 相似文献
19.
Jochen Glaser Simone Dill Michael Marzini Hermann A. Mayer H.‐Jürgen Meyer 《无机化学与普通化学杂志》2001,627(5):1090-1094
(Meta)stable CaC2 One out of four modifications of CaC2 is the so‐called metastable Calcium Carbide, CaC2‐III, which was synthesized as pure material. It forms by heating monoclinic CaC2‐II (C2/c) above 150 °C and remains stable after cooling down to room temperature. The structure was refined from X‐ray powder patterns (C2/m, Z = 4, a = 722.6(1) pm, b = 385.26(7) pm, c = 737.6(1) pm, β = 107.345(2)°). After grinding CaC2‐III transforms back into CaC2‐II. Heating CaC2‐III induces a reversible phase transition into the cubic modification (CaC2‐IV) at 460 °C. Differences between the three different structures of CaC2 I–III, being stable at ambient conditions are also shown by 13C‐MAS‐NMR measurements, especially the presence of two distinct types of carbon atoms in the structure of the title compound. 相似文献
20.
We show how to apply a general theoretical approach to nonequilibrium statistical mechanics, called Maximum Caliber, originally suggested by E. T. Jaynes [Annu. Rev. Phys. Chem. 31, 579 (1980)], to a problem of two-state dynamics. Maximum Caliber is a variational principle for dynamics in the same spirit that Maximum Entropy is a variational principle for equilibrium statistical mechanics. The central idea is to compute a dynamical partition function, a sum of weights over all microscopic paths, rather than over microstates. We illustrate the method on the simple problem of two-state dynamics, A<-->B, first for a single particle, then for M particles. Maximum Caliber gives a unified framework for deriving all the relevant dynamical properties, including the microtrajectories and all the moments of the time-dependent probability density. While it can readily be used to derive the traditional master equation and the Langevin results, it goes beyond them in also giving trajectory information. For example, we derive the Langevin noise distribution rather than assuming it. As a general approach to solving nonequilibrium statistical mechanics dynamical problems, Maximum Caliber has some advantages: (1) It is partition-function-based, so we can draw insights from similarities to equilibrium statistical mechanics. (2) It is trajectory-based, so it gives more dynamical information than population-based approaches like master equations; this is particularly important for few-particle and single-molecule systems. (3) It gives an unambiguous way to relate flows to forces, which has traditionally posed challenges. (4) Like Maximum Entropy, it may be useful for data analysis, specifically for time-dependent phenomena. 相似文献