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411.
Dr. Romain Tessier Prof. Dr. Raj Kumar Nandi Brendan G. Dwyer Dr. Daniel Abegg Charlotte Sornay Dr. Javier Ceballos Stéphane Erb Dr. Sarah Cianférani Dr. Alain Wagner Dr. Guilhem Chaubet Prof. Dr. Alexander Adibekian Prof. Dr. Jerome Waser 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(27)
412.
Nicolas Kerisit Romain Ligny Etienne S. Gauthier Jean‐Paul Gugan Loïc Toupet Jean‐Claude Guillemin Yann Trolez 《Helvetica chimica acta》2019,102(3)
The synthesis of 5‐bromopenta‐2,4‐diynenitrile (BrC5N) in three steps from commercially available compounds is reported. Reacting 5‐bromopenta‐2,4‐diynenitrile with secondary amines led to the formation of stable butadiynamines or enynenitriles, depending on the nature of the amine reactant. The reaction of 5‐bromopenta‐2,4‐diynenitrile with simple terminal alkynes in the presence of secondary amines, copper, and palladium catalysts, provided a straightforward access to original polyfunctional carbon‐rich scaffolds. In this work, different alkynes and secondary amines were tested, which allowed for the preparation of a family of substituted dienes. Given the high synthetic potential of 5‐bromopenta‐2,4‐diynenitrile, we also prepared iodinated counterparts of this compound, that is, 5‐iodopenta‐2,4‐diynenitrile and its lower homologue 3‐iodopropiolonitrile. The UV‐visible spectrum of some relevant compounds was also recorded. 相似文献
413.
Romain Membrat Alexandre Vasseur Laurent Giordano Alexandre Martinez Didier Nuel 《Tetrahedron letters》2019,60(3):240-243
A convenient method to access a broad variety of N-alkyl-(2,2,6,6)-tetramethylpiperidin-4-ol compounds is reported. The thermal treatment of a mixture of (2,2,6,6)-tetramethylpiperidin-4-ol and allyl or benzyl bromide derivatives gave the corresponding N–alkylated compounds in good yields while leaving the hydroxyl functional group intact. Whereas 40?h were needed to reach complete conversion, microwave irradiation allowed the reaction time to be reduced (20?min) and improved the yields in most cases. 相似文献
414.
415.
416.
Romain Dabre Achim Schwämmle Michael Lämmerhofer Wolfgang Lindner 《Journal of chromatography. A》2009,1216(16):3473-3479
Thiol-modified silica is often used as an intermediate product for further synthesis of modified stationary phases for chromatography or purification processes. Different conditions were used to synthesize such thiol-modified particles, but systematic optimizations remained scarce. In this study the reaction conditions for the synthesis of mercaptopropyl-modified silica were optimized. The general synthetic method consists in slurrying the silica gel in toluene before adding 3-mercaptopropyldimethoxymethylsilane together with a tertiary amine as catalyst (here dimethylaminopyridine). Reaction time and temperature were optimized using a full factorial design of experiment (DoE) from 3 to 25 h with temperature varying between 45 and 105 °C. The surface coverage of the silica with mercaptopropyl-groups was analyzed by two different ways (elemental analysis and chemical surface reaction with 2,2′-dipyridyl disulfide followed by HPLC-UV analysis of stoichiometrically liberated pyridyl-2-thione). We obtained a three-dimensional (3D) plot of the surface coverage as a function of reaction time and temperature. The arch-shaped hyperplane allowed us to determine an optimum with regard to time and temperature, which yields to the highest surface coverage possible. We also verified that the increase of the surface coverage does not lead to a decrease of the stability of the surface modification by subjecting the gels to treatment with high temperature and acidic conditions. The stability was monitored by different chromatographic methods. Moreover, 29Si cross-polarization-magic angle spinning (CP-MAS) NMR spectra of materials prepared by different conditions allowed to confirm that the Si species on the surface were essentially the same, while there was only a minute difference in signal intensities for the individual Si species for materials obtained by distinct temperatures. 相似文献
417.
Nuria Rendón Dr. Romain Berthoud Dr. Frédéric Blanc Dr. David Gajan Tarun Maishal Dr. Jean‐Marie Basset Dr. Christophe Copéret Dr. Anne Lesage Dr. Lyndon Emsley Prof. Smaranda C. Marinescu Rojendra Singh Dr. Richard R. Schrock Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(20):5083-5089
Silica supports : Well‐defined silica‐supported Mo–alkylidene complexes containing one alkoxy/aryloxy substituent are selectively obtained by grafting onto silica either well‐defined molecular bis(alkoxy) or alkoxyamido complexes (see scheme). These silica‐supported complexes are highly efficient catalyst precursors for the metathesis of acyclic alkenes. However, they display poor performances in ring‐closing metathesis reactions, possibly due to the relatively large siloxy ligand (silica) inducing a greater rigidity.
418.
Romain?Ducasse Luca?RossiEmail author 《Calculus of Variations and Partial Differential Equations》2018,57(5):142
We investigate the large time behavior of solutions of reaction–diffusion equations with general reaction terms in periodic media. We first derive some conditions which guarantee that solutions with compactly supported initial data invade the domain. In particular, we relate such solutions with front-like solutions such as pulsating traveling fronts. Next, we focus on the homogeneous bistable equation set in a domain with periodic holes, and specifically on the cases where fronts are not known to exist. We show how the geometry of the domain can block or allow invasion. We finally exhibit a periodic domain on which the propagation takes place in an asymmetric fashion, in the sense that the invasion occurs in a direction but is blocked in the opposite one. 相似文献
419.
Romain Dujardin 《Geometric And Functional Analysis》2010,20(2):398-415
We give the first examples of positive closed currents T in ${{\mathbb C}^2}We give the first examples of positive closed currents T in
\mathbb C2{{\mathbb C}^2} with continuous potentials, T ùT = 0{T \wedge T = 0}, and whose supports do not contain any holomorphic disk. This gives in particular an affirmative answer to a question of
Forn?ss and Levenberg. We actually construct examples with potential of class C
1,α
for all α < 1. This regularity is expected to be essentially optimal. 相似文献
420.