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Dr. Pilar Ventosa‐Andrés Dr. Agustina La‐Venia Dr. Carlos Alfonso Barea Ripoll Dr. Ludmila Hradilová Dr. Viktor Krchňák 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(37):13112-13119
Herein, we describe the synthesis of molecular scaffolds consisting of medium‐sized fused heterocycles using amino acids, which are some of the most useful building blocks used by nature as well as chemists to create structural diversity. The acyclic precursors were assembled by using traditional Merrifield solid‐phase peptide synthesis, and cyclization was carried out through acid‐mediated tandem endocyclic N‐acyliminium ion formation, followed by nucleophilic addition with internal nucleophiles. The synthesis of molecular scaffolds consisting of seven‐, eight‐, and nine‐membered rings proceeded with full stereocontrol of the newly generated stereogenic center in most cases. 相似文献
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Why Is the Spontaneous Deprotonation of [Cu(uracil)2]2+ Complexes Accompanied by Enolization of the System? 下载免费PDF全文
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
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Simultaneous Aromatic–Beryllium Bonds and Aromatic–Anion Interactions: Naphthalene and Pyrene as Models of Fullerenes,Carbon Single‐Walled Nanotubes,and Graphene 下载免费PDF全文
Dr. Marta Marín‐Luna Prof. Ibon Alkorta Prof. José Elguero Prof. Otilia Mó Prof. Manuel Yáñez 《Chemphyschem》2015,16(12):2680-2686
The possibility of forming stable BeR2:ArH:Y? (R=H, F, Cl; ArH=naphthalene, pyrene; Y=Cl, Br) ternary complexes in which the beryllium compounds and anions are located on the opposite sides of an extended aromatic system is explored by means of MP2/aug‐cc‐pVDZ ab initio calculations. Comparison of the electron‐density distribution of these ternary complexes with the corresponding BeR2:ArH and ArH:Y? binary complexes reveals the existence of significant cooperativity between the two noncovalent interactions in the triads. The energetic effects of this cooperativity are quantified by evaluation of the three‐body interaction energy Δ3E in the framework of the many‐body interaction‐energy (MBIE) approach. Although an essential component of the interaction energies is electrostatic and is well reflected in the changes in the molecular electrostatic potential of the aromatic system on complexation, strong polarization effects, in particular for the BeR2:ArH interactions, also play a significant role. The charge transfers associated with these polarization effects are responsible for significant distortion of both the BeR2 and the aromatic moieties. The former are systematically bent in all the complexes, and the latter are curved to a degree that depends on the nature of the R substituents of the BeR2 subunit. 相似文献
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M. Sc. Elena Kusevska Dr. M. Merced Montero-Campillo Prof. Otilia Mó Prof. Manuel Yáñez 《Angewandte Chemie (International ed. in English)》2017,56(24):6788-6792
Owing to its versatility in synthetic chemistry, TPB (tris[2-diisopropylphospino)phenyl]borane) is a very important frustrated Lewis Pair. The unusual stability of the neutral radical (TPB)Cu has been related to the presence of a one-electron B−Cu bond. Herein we show, through the use of different computational chemistry methods, that the existence and nature of this kind of A⋅⋅⋅M bond (A=donor atom, M=transition metal) depends on the surrounding chemical structure, and can be genuine one-electron sigma bonds only if appropriate metal ligands (Y), able to trap the charge in the desired region, are chosen. This ability is modulated by the subtle balance between the electronegativity of the different atoms along the A⋅⋅⋅M⋅⋅⋅Y bond paths. Most importantly, contrary to many TPB complexes in which boron acts as a Lewis acid, in one-electron-bond-containing structures boron behaves as a Lewis base. 相似文献
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Alexander. V. Zuraev Yuri V. Grigoriev Ludmila S. Ivashkevich Alexander S. Lyakhov Oleg A. Ivashkevich 《无机化学与普通化学杂志》2017,643(19):1215-1219
A new catalyst for cross‐coupling synthesis of 1,4‐diphenylbutadiyne‐1,3 was prepared by thermolysis of copper(II) poly‐5‐vinyltetrazolate. It presents heterogeneous catalyst, in which copper nanoparticles are supported on polymeric matrix surface. The catalyst is recovered, recycled, and shows high catalytic activity in cross‐coupling synthesis of 1,4‐diphenylbutadiyne‐1,3. The reaction proceeds in aerobic conditions at room temperature in the presence of pyridine. 相似文献
9.
An analysis of the effects induced by F, Cl, and Br-substituents at the α-position of both, the hydroxyl or the amino group for a series of amino-alcohols, HOCH2(CH2)nCH2NH2 (n = 0–5) on the strength and characteristics of their OH···N or NH···O intramolecular hydrogen bonds (IMHBs) was carried out through the use of high-level G4 ab initio calculations. For the parent unsubstituted amino-alcohols, it is found that the strength of the OH···N IMHB goes through a maximum for n = 2, as revealed by the use of appropriate isodesmic reactions, natural bond orbital (NBO) analysis and atoms in molecules (AIM), and non-covalent interaction (NCI) procedures. The corresponding infrared (IR) spectra also reflect the same trends. When the α-position to the hydroxyl group is substituted by halogen atoms, the OH···N IMHB significantly reinforces following the trend H < F < Cl < Br. Conversely, when the substitution takes place at the α-position with respect to the amino group, the result is a weakening of the OH···N IMHB. A totally different scenario is found when the amino-alcohols HOCH2(CH2)nCH2NH2 (n = 0–3) interact with BeF2. Although the presence of the beryllium derivative dramatically increases the strength of the IMHBs, the possibility for the beryllium atom to interact simultaneously with the O and the N atoms of the amino-alcohol leads to the global minimum of the potential energy surface, with the result that the IMHBs are replaced by two beryllium bonds. 相似文献
10.
Michael A. Pudovik Ludmila K. Kibardina Alexander R. Burilov 《Phosphorus, sulfur, and silicon and the related elements》2019,194(1-2):134-138
The reaction of azomethines of pyridoxal or alkoxyfuropyridines with phosphorus acids produces new salt derivatives. 相似文献