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51.
Léo Birbaum Dr. Laurent Gillard Prof. Hélène Gérard Prof. Hassan Oulyadi Dr. Guillaume Vincent Prof. Xavier Moreau Dr. Michael De Paolis Prof. Isabelle Chataigner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(60):13688-13693
3-Nitroindoles are easily reacted with highly substituted γ-allenoates in the presence of a commercially available phosphine catalyst. For instance, allenoates derived from biomolecules such as amino and deoxycholic acids are combined for the first time with 3-nitroindole. The corresponding dearomatized (3+2) tricyclic cycloadducts are obtained as α-regioisomers exclusively. DFT computations shed light on this multi-step reaction mechanism and on the selectivities observed in the sequence. 相似文献
52.
Bernhard Wölfl Dr. Guillaume Mata Prof. Alois Fürstner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(1):255-259
The macrocyclic core of the cytotoxic marine natural product callyspongiolide ( 1 ) was forged by ring-closing alkyne metathesis (RCAM) of an ynoate precursor using a molybdenum alkylidyne complex endowed with triarylsilanolate ligands as the catalyst. This result is remarkable in view of the failed attempts documented in the literature at converting electron deficient alkynes with the aid of more classical catalysts. The subsequent Z-selective semi-reduction of the resulting cycloalkyne by hydrogenation over nickel boride required careful optimization in order to minimize overreduction and competing dehalogenation of the compound's alkenyl iodide terminus as needed for final attachment of the side chain of 1 by Sonogashira coupling. The required cyclization precursor itself was prepared via Kocienski olefination. 相似文献
53.
Guillaume Erbland Dr. Seifallah Abid Yohan Gisbert Nathalie Saffon-Merceron Yuichiro Hashimoto Leonardo Andreoni Théo Guérin Dr. Claire Kammerer Prof. Dr. Gwénaël Rapenne 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(71):16328-16339
The design and synthesis of two families of molecular-gear prototypes is reported, with the aim of assembling them into trains of gears on a surface and ultimately achieving controlled intermolecular gearing motion. These piano-stool ruthenium complexes incorporate a hydrotris(indazolyl)borate moiety as tripodal rotation axle and a pentaarylcyclopentadienyl ligand as star-shaped cogwheel, equipped with five teeth ranging from pseudo-1D aryl groups to large planar 2D paddles. A divergent synthetic approach was followed, starting from a pentakis(p-bromophenyl)cyclopentadienyl ruthenium(II) complex as key precursor or from its iodinated counterpart, obtained by copper-catalyzed aromatic Br/I exchange. Subsequent fivefold cross-coupling reactions with various partners allowed high structural diversity to be reached and yielded molecular-gear prototypes with aryl-, carbazole-, BODIPY- and porphyrin-derived teeth of increasing size and length. 相似文献
54.
Manuel Bernard Ghislain Lartigue Guillaume Balarac Vincent Moureau Guillaume Puigt 《国际流体数值方法杂志》2020,92(11):1551-1583
In this article, a new framework to design high-order approximations in the context of node-centered finite volumes on simplicial meshes is proposed. The major novelty of this method is that it relies on very simple and compact differential operators, which is a critical point to achieve good performances in the High-performance computing context. This method is based on deconvolution between nodal and volume-average values, which can be conducted to any order. The interest of the new method is illustrated through three different applications: mesh-to-mesh interpolation, levelset curvature computation, and numerical scheme for convection. Higher order can also be achieved within the present framework by introducing high-rank tensors. Although these tensors feature much symmetries, their manipulation can quickly become an overwhelming task. For this reason and without loss of generality, the present articles are limited to third-order expansion. This method, although tightly connected to the k-exact schemes theory, does not rely on successive corrections: the high-order property is obtained in a single operation, which makes them more attractive in terms of performances. 相似文献
55.
56.
Wenbin Guo Dr. Nathalie Daro Dr. Sébastien Pillet Dr. Mathieu Marchivie Dr. El-Eulmi Bendeif Dr. Elodie Tailleur Dr. Kittipong Chainok Dominique Denux Dr. Guillaume Chastanet Prof. Philippe Guionneau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(57):12927-12930
The current craze for research around the spin crossover phenomenon can be justified to some extent by the mechanical properties due to the decrease of volume associated with the transition of the metal ion from the HS state to the LS state. As demonstrated here, the molecular complex [Fe(PM-pBrA)2(NCS)2] exhibits, on the contrary, an increase of the unit-cell volume from HS to LS. This counter-intuitive and unprecedented behavior that concerns both the thermal and the photoexcited spin conversions is revealed by a combination of single-crystal and powder X-ray diffraction complemented by magnetic measurements. Interestingly, this abnormal volume change appears concomitant with the wide rotation of a phenyl ring which induces a drastic modification, though reversible, of the structural packing within the crystal. In addition, the light-induced HS state obtained through the Light-Induced Excited Spin-State Trapping shows a remarkably high relaxation temperature, namely T(LIESST), of 109 K, one of the highest so far reported. The above set of quite unusual characteristics opens up new fields of possibilities within the development of spin crossover materials. 相似文献
57.
Guillaume Pisella Alec Gagnebin Prof. Dr. Jérôme Waser 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(45):10199-10204
Multicomponent reactions provide efficient means to access molecular complexity. Herein, we report a copper-catalyzed three-component reaction of diazo compounds, alcohols and ethynyl benziodoxole (EBX) reagents for the synthesis of propargyl ethers. Extensive variations of the three partners of the reaction is possible, leading to highly functionalized and structurally diverse products under mild conditions. Alkynylation of a copper ylide intermediate is postulated as key step for this transformation. 相似文献
58.
Emel Önal Cheng Zhang Derya Davarcı Ümit İşci Guillaume Pilet Andrew K. Whittaker Fabienne Dumoulin 《Tetrahedron letters》2018,59(6):521-523
A cyclotriphosphazene substituted with six 3,5-bis(trifluoromethyl) benzyloxy units was designed as a novel 19F MRI contrast agent. The resulting molecule has 36 magnetically equivalent fluorine atoms and exhibited suitable MRI properties with high imaging sensitivity, confirming the proof-of-concept as a convenient scaffold for the production of new 19F MRI contrasts agents. 相似文献
59.
P. Boccaccio L. Vannucci R.A. Ricci G. Vannini R. Dona I. Massa J.P. Coffin P. Fintz G. Guillaume F. Jundt F. Rami P. Wagner 《The European Physical Journal A - Hadrons and Nuclei》1998,1(4):399-406
We studied the sequential binary decay of the systems 32S+45Sc, 76Ge, 89Y, 59Co, 63Cu and 19F+63Cu induced by collisions at ≃6 MeV·A. The two stages of the process have reaction-times compatible with the dynamics of different mechanisms. The study of the
excitation energy partition shows that the reaction mechanism of the first step has influence on the de-excitation of the
primary fragments producing two decay components which have different time scale.
Received: 25 March 1997 / Revised version: 2 December 1997 相似文献
60.
Summary. In shape optimization problems, each computation of
the cost function by the finite element method
leads to an expensive analysis. The use of the second order derivative
can help to reduce the number of analyses. Fujii ([4], [10])
was the first to study this problem. J. Simon [19] gave the second order
derivative for the Navier-Stokes
problem, and the authors describe in [8], [11], a method which gives an
intrinsic expression of the first and second order derivatives on the
boundary
of the involved domain.
In this paper we study higher order derivatives. But one can ask
the following questions:
-- are they expensive to calculate?
-- are they complicated to use?
-- are they imprecise?
-- are they useless?
\medskip\noindent
At first sight, the answer seems to be positive, but classical results of
V. Strassen [20] and J. Morgenstern [13] tell us that the higher order
derivatives are not expensive to calculate, and can be computed
automatically. The purpose of this paper is to give an answer to the third
question by proving that the higher order derivatives of a function can be
computed with the same precision as the function itself.
We prove also that the derivatives so computed are
equal to the derivatives of the discrete problem (see Diagram 1). We
call the discrete
problem the finite dimensional problem processed by the computer. This result
allows the use of automatic differentiation ([5], [6]), which works only on
discrete problems.
Furthermore, the computations of Taylor's expansions
which are proposed at the end of this paper, could be a partial answer to
the last question.
Received January 27, 1993/Revised version received July 20, 1993 相似文献