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991.
A bifunctional tetraethylene glycol (TEG) linker was prepared and used as an initiator for the synthesis of the first two generations of dendrigraft poly-l-lysines (DGL). The key steps involved the desymmetrization of TEG by introduction of an amine group after activation of a terminal hydroxyl group and of a conveniently protected aminooxy functionality at the other end. Initiation of l-lysine N-carboxyanhydride polymerization by the terminal amine yielded generations 1 and 2 of DGL in which a subsequent functionalization of the aminooxy group by ligation with entities bearing an aldehyde group turned out to be feasible. 相似文献
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João X. de Araújo-Júnior Martine Schmitt Pascal Benderitter 《Tetrahedron letters》2006,47(34):6125-6128
Regioselective desymmetrization of 4-substituted pyridazin-3,6-diones using sterically hindered 2,4,6-triisopropylphenyl-sulfonylchloride allowed efficient sequential palladium cross-coupling reactions. 相似文献
996.
997.
Multi‐frequency (S,X, Q and W‐band) EPR and ENDOR Study of Vanadium(IV) Incorporation in the Aluminium Metal–Organic Framework MIL‐53 下载免费PDF全文
Irena Nevjestić Hannes Depauw Dr. Karen Leus Dr. Vidmantas Kalendra Dr. Ignacio Caretti Prof. Gunnar Jeschke Prof. Sabine Van Doorslaer Prof. Freddy Callens Prof. Pascal Van Der Voort Dr. Henk Vrielinck 《Chemphyschem》2015,16(14):2968-2973
Doping the well‐known metal–organic framework MIL‐53(Al) with vanadium(IV) ions leads to significant changes in the breathing behaviour and might have repercussions on the catalytic behaviour as well. To understand the properties of such a doped framework, it is necessary to determine where dopant ions are actually incorporated. Electron paramagnetic resonance (EPR) and electron–nuclear double resonance (ENDOR) are applied to reveal the nearest environment of the paramagnetic vanadium(IV) dopant ions. EPR spectra of as‐synthesised vanadium‐doped MIL‐53 are recorded at S‐, X‐, Q‐ and W‐band microwave frequencies. The EPR spectra suggest that at low dopant concentrations (1.0–2.6 mol %) the vanadium(IV) ions are well dispersed in the matrix. Varying the vanadium dopant concentration within this range or the dopant salt leads to the same dominant EPR component. In the ENDOR spectra, hyperfine (HF) interactions with 1H, 27Al and 51V nuclei are observed. The HF parameters extracted from simulations strongly suggest that the vanadium(IV) ions substitute Al in the framework. 相似文献
998.
Self‐Relay Gold(I)‐Catalyzed Pictet–Spengler/Cyclization Cascade Reaction for the Rapid Elaboration of Pentacyclic Indole Derivatives 下载免费PDF全文
Valérian Gobé Dr. Pascal Retailleau Dr. Xavier Guinchard 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(49):17587-17590
Gold‐catalyzed cascade reactions allow the rapid elaboration of pentacyclic indolo[2,3‐a]quinolizidines from N‐allyl tryptamines and ortho‐alkynylarylaldehydes. The tandem process combines a gold‐catalyzed Pictet‐Spengler reaction and a cyclization occurring concomitantly with an allyl transfer from the nitrogen atom to the stilbene function. Various substituted allyls were successfully transferred, furnishing the products in yields typically ranging from 60–98 % in high diastereoselectivity. Tryptamines bearing a butenol chain undergo an additional cyclization to chiral hemiaminals in high diastereoselectivities. 相似文献
999.
Synthesis of New Phosphahelicene Scaffolds and Development of Gold(I)‐Catalyzed Enantioselective Allenene Cyclizations 下载免费PDF全文
Paul Aillard Dr. Pascal Retailleau Dr. Arnaud Voituriez Dr. Angela Marinetti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(34):11989-11993
This paper reports on the development of an efficient synthesis of enantiopure phospha[6]helicenes through a [2+2+2] alkyne cyclotrimerization reaction. The corresponding gold complexes proved to be highly efficient both in terms of catalytic activity and enantioselectivity in [2+2] and [4+2] cycloaddition reactions. Furthermore, in the presence of an external nucleophile, such as water or alcohols, the tandem cyclization/addition reactions take place in high yields and excellent diastereo‐ and enantioselectivities. 相似文献
1000.
Well‐Defined Four‐Coordinate Iron(II) Complexes For Intramolecular Hydroamination of Primary Aliphatic Alkenylamines 下载免费PDF全文
Dr. Elise Bernoud Dr. Pascal Oulié Dr. Régis Guillot Dr. Mohamed Mellah Dr. Jérôme Hannedouche 《Angewandte Chemie (International ed. in English)》2014,53(19):4930-4934
Despite the growing interest in iron catalysis and hydroamination reactions, iron‐catalyzed hydroamination of unprotected primary aliphatic amines and unactivated alkenes has not been reported to date. Herein, a novel well‐defined four‐coordinate β‐diketiminatoiron(II) alkyl complex is shown to be an excellent precatalyst for the highly selective cyclohydroamination of primary aliphatic alkenylamines at mild temperatures (70–90 °C). Both empirical kinetic analyses and the reactivity of an isolated iron(II) amidoalkene dimer, [LFe(NHCH2CPh2CH2CH?CH2)]2 favor a stepwise σ‐insertive mechanism that entails migratory insertion of the pendant alkene into an iron–amido bond associated with a rate‐determining aminolysis step. 相似文献