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71.
Scalable Synthesis of the Potent HIV Inhibitor BMS‐986001 by Non‐Enzymatic Dynamic Kinetic Asymmetric Transformation (DYKAT)
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Dr. Adrian Ortiz Dr. Tamas Benkovics Dr. Gregory L. Beutner Dr. Zhongping Shi Dr. Michael Bultman Dr. Jeffrey Nye Dr. Chris Sfouggatakis Dr. David R. Kronenthal 《Angewandte Chemie (International ed. in English)》2015,54(24):7185-7188
Described herein is the synthesis of BMS‐986001 by employing two novel organocatalytic transformations: 1) a highly selective pyranose to furanose ring tautomerization to access an advanced intermediate, and 2) an unprecedented small‐molecule‐mediated dynamic kinetic resolution to access a variety of enantiopure pyranones, one of which served as a versatile building block for the multigram, stereoselective, and chromatography‐free synthesis of BMS‐986001. The synthesis required five chemical transformations and resulted in a 44 % overall yield. 相似文献
72.
Computational Study of Proton Transfer in Tautomers of 3‐ and 5‐Hydroxypyrazole Assisted by Water
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Dr. Cristina Trujillo Dr. Goar Sánchez‐Sanz Prof. Ibon Alkorta Prof. José Elguero 《Chemphyschem》2015,16(10):2140-2150
The tautomerism of 3‐ and 5‐hydroxypyrazole is studied at the B3LYP, CCSD and G3B3 computational levels, including the gas phase, PCM–water effects, and proton transfer assisted by water molecules. To understand the propensity of tautomerization, hydrogen‐bond acidity and basicity of neutral species is approached by means of correlations between donor/acceptor ability and H‐bond interaction energies. Tautomerism processes are highly dependent on the solvent environment, and a significant reduction of the transition barriers upon solvation is seen. In addition, the inclusion of a single water molecule to assist proton transfer decreases the barriers between tautomers. Although the second water molecule further reduces those barriers, its effect is less appreciable than the first one. Neutral species present more stable minima than anionic and cationic species, but relatively similar transition barriers to anionic tautomers. 相似文献
73.
Why Is the Spontaneous Deprotonation of [Cu(uracil)2]2+ Complexes Accompanied by Enolization of the System?
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Oriana Brea Prof. Manuel Yáñez Prof. Otilia Mó Dr. Al Mokhtar Lamsabhi 《Chemphyschem》2015,16(11):2375-2382
The reaction‐force formalism is applied to carry out a detailed analysis of the mechanisms behind the enolization processes undergone by the complexes formed on interaction of uracil dimers with Cu2+ ions after spontaneous deprotonation of the resulting complexes. These enolization processes apparently involve a single proton transfer (PT) from an NH group to a carbonyl group of the same uracil moiety, which should involve a rather high activation barrier that prevents the process occurring. However, the reaction‐force, chemical‐potential, and electronic‐flux profiles unambiguously indicate that the actual mechanism involves three low‐barrier elementary steps, and this explains why enolization of the [Cu(uracil?H)(uracil)]+ complexes is a highly facile, assisted PT process. All of the observed PT processes show a typical profile for both the chemical potential and the electronic flux associated with the bond‐breaking and the bond‐formation processes. 相似文献
74.
Rafael C. Machado Richard M. Grazul Renata Diniz 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(7):564-569
In the solid state, crystals of both 1‐(7‐chloro‐1,4‐dihydroquinolin‐4‐ylidene)thiosemicarbazide–methanol–water (2/1/1), 2C10H9ClN4S·CH3OH·H2O, (I), and its hydrochloride salt {systematic name: [(7‐chloro‐1,4‐dihydroquinolin‐4‐ylidene)azaniumyl]thiourea chloride}, C10H10ClN4S+·Cl−, (II), assume the imine tautomeric form, contrary to other 4‐amino‐7‐chloroquinolines. Of particular interest are the N—C bond lengths, which have appreciable double‐bond character, and the C—N—C aromatic ring bond angle. Both of these parameters have been studied extensively in 4‐amino‐substituted quinolines. The crystal structures of (I) and (II) in this study provide interesting examples of the amino–imino tautomerism which exists in this class of compound and is, to the best of our knowledge, hitherto unreported. 相似文献
75.
Covalent Grafting of Coordination Polymers on Surfaces: The Case of Hybrid Valence Tautomeric Interphases
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Pablo González‐Monje Dr. Fernando Novio Dr. Daniel Ruiz‐Molina 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(28):10094-10099
We have developed a novel approach for grafting coordination polymers, structured as nanoparticles bearing surface reactive carboxylic groups, to amino‐functionalized surfaces through a simple carbodiimide‐mediated coupling reaction. As a proof‐of‐concept to validate our approach, and on the quest for novel hybrid interphases with potential technological applications, we have used valence tautomeric nanoparticles exhibiting spin transition at or around room temperature. SEM and AFM characterization reveal that the nanoparticles were organized chiefly into a single monolayer while X‐ray photoelectron spectroscopy (XPS) measurements confirm that the nanoparticles retain a temperature‐induced electronic redistribution upon surface anchorage. Our results represent an effective approach towards the challenging manufacture of coordination polymers. 相似文献
76.
The variations in topology of the electron density along the reaction paths of the keto-enol tautomerism of acetaldehyde, the pinacol rearrangement of protonated 1,2-ethanediol, and the unimolecular decomposition of methanediol, were studied as examples of hydrogen transfer between, respectively, C?O, C?C, and O?O atoms. The evolution of atomic charges, determined using two different atomic partitionings (AIM and Hirshfeld), indicates that the main electronic charge transfer in keto-enol tautomerism takes place between the migrating hydrogen and the carbon of the carbonyl group. The topology of the electron density demonstrates that a hydrogen-bridge structure is never formed along the reaction path of the pinacol rearrangement. The methanediol decomposition follows a concerted mechanism with very small variations in the atomic charges. 相似文献
77.
78.
A. P. Hyengoyan K. A. Eliazyan V. A. Pivazyan E. A. Khazaryan V. V. Dovlatyan 《Chemistry of Heterocyclic Compounds》2005,41(8):1062-1065
We have used 1H NMR to study the amine-imine tautomerism of some esters and amides of 2-N-labeled 4-methylthiazole-5-carboxylic acids and
5-carbamic acids. We have shown that the nature of the substituents of the 2-NHR1, 5-COR2, or 5-NHCOR2 groups affects that position of the tautomeric equilibrium.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1240–1243, August, 2005. 相似文献
79.
Using fixed tautomeric structures of 3,4-dihydropyrromethenones and 2,3-dihydrobilatrienes-abc (N- and O-alkylation) a prevalence of the lactam and bis-lactam form over lactimes by several orders of magnitude could be deduced. Although there are complications arising from side reactions of the pyrrolidinone fragment, protonation equilibria provided valuable clues for this result which is nicely complemented by NMR-, IR and UV-VIS data.
Herrn Prof. Dr.J. Derkosch, Universität Wien, zum 60. Geburtstag gewidmet. 相似文献
80.