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A new and efficient synthesis of 2‐[1‐alkyl‐5,6‐bis(alkoxycarbonyl)‐1,2,3,4‐tetrahydro‐2‐oxopyridin‐3‐yl]acetic acid derivatives by a one‐pot three‐component reaction between primary amine, dialkyl acetylenedicarboxylate, and itaconic anhydride (=3,4‐dihydro‐3‐methylidenefuran‐2,5‐dione) is reported. The reaction was performed without catalyst and under solvent‐free conditions with excellent yields. Notably, the ready availability of the starting materials, and the high level of practicability of the reaction and workup make this approach an attractive complementary method to access to unknown 2‐[1‐alkyl‐5,6‐bis(alkoxycarbonyl)‐1,2,3,4‐tetrahydro‐2‐oxopyridin‐3‐yl]acetic acid derivatives. The structures were corroborated spectroscopically (IR, 1H‐ and 13C‐NMR, and EI‐MS) and by elemental analyses. A plausible mechanism for this type of domino Michael addition? cyclization reaction is proposed (Scheme 2). 相似文献
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Gunar Hadiprono 《Nachrichten aus der Chemie》2001,49(6):768-769
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Starting from perfluoroheptane, saturated aqueous potassium carbonate solution, methanol, toluene and suitable dyes, a three‐phasic mixture is prepared initially. After shaking – not only stirring – four layers develop. Addition of pentane changes the sequence of two layers. The layers are added in a new sequence and the way of mixing demonstrates the complexity of multi‐phasic systems. 相似文献
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Venkateshwarlu Gurram Dr. Narender Pottabathini Ramesh Garlapati Dr. Avinash B. Chaudhary Dr. Balaram Patro Prof. Mahesh K. Lakshman 《化学:亚洲杂志》2012,7(8):1853-1861
Reaction conditions for the C? C cross‐coupling of O6‐alkyl‐2‐bromo‐ and 2‐chloroinosine derivatives with aryl‐, hetaryl‐, and alkylboronic acids were studied. Optimization experiments with silyl‐protected 2‐bromo‐O6‐methylinosine led to the identification of [PdCl2(dcpf)]/K3PO4 in 1,4‐dioxane as the best conditions for these reactions (dcpf=1,1′‐bis(dicyclohexylphosphino)ferrocene). Attempted O6‐demethylation, as well as the replacement of the C‐6 methoxy group by amines, was unsuccessful, which led to the consideration of Pd‐cleavable groups such that C? C cross‐coupling and O6‐deprotection could be accomplished in a single step. Thus, inosine 2‐chloro‐O6‐allylinosine was chosen as the substrate and, after re‐evaluation of the cross‐coupling conditions with 2‐chloro‐O6‐methylinosine as a model substrate, one‐step C? C cross‐coupling/deprotection reactions were performed with the O6‐allyl analogue. These reactions are the first such examples of a one‐pot procedure for the modification and deprotection of purine nucleosides under C? C cross‐coupling conditions. 相似文献
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Dense or Porous Packing? Two‐Dimensional Self‐Assembly of Star‐Shaped Mono‐, Bi‐, and Terpyridine Derivatives
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Dr. Daniel Trawny Philomena Schlexer Krista Steenbergen Prof. Dr. Jürgen P. Rabe Prof. Dr. Beate Paulus Prof. Dr. Hans‐Ulrich Reissig 《Chemphyschem》2015,16(5):949-953
The self‐assembly behavior of five star‐shaped pyridyl‐functionalized 1,3,5‐triethynylbenzenes was studied at the interface between an organic solvent and the basal plane of graphite by scanning tunneling microscopy. The mono‐ and bipyridine derivatives self‐assemble in closely packed 2D crystals, whereas the derivative with the more bulky terpyridines crystallizes with porous packing. DFT calculations of a monopyridine derivative on graphene, support the proposed molecular model. The calculations also reveal the formation of hydrogen bonds between the nitrogen atoms and a hydrogen atom of the neighboring central unit, as a small nonzero tunneling current was calculated within this region. The title compounds provide a versatile model system to investigate the role of multivalent steric interactions and hydrogen bonding in molecular monolayers. 相似文献
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Chuanqi Zhao Geng Qin Jingsheng Niu Zhao Wang Chunyu Wang Jinsong Ren Xiaogang Qu 《Angewandte Chemie (International ed. in English)》2021,60(1):432-438
The COVID‐19 pandemic caused by SARS‐CoV‐2 has become a global threat. Understanding the underlying mechanisms and developing innovative treatments are extremely urgent. G‐quadruplexes (G4s) are important noncanonical nucleic acid structures with distinct biofunctions. Four putative G4‐forming sequences (PQSs) in the SARS‐CoV‐2 genome were studied. One of them (RG‐1), which locates in the coding sequence region of SARS‐CoV‐2 nucleocapsid phosphoprotein (N), has been verified to form a stable RNA G4 structure in live cells. G4‐specific compounds, such as PDP (pyridostatin derivative), can stabilize RG‐1 G4 and significantly reduce the protein levels of SARS‐CoV‐2 N by inhibiting its translation both in vitro and in vivo. This result is the first evidence that PQSs in SARS‐CoV‐2 can form G4 structures in live cells, and that their biofunctions can be regulated by a G4‐specific stabilizer. This finding will provide new insights into developing novel antiviral drugs against COVID‐19. 相似文献
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Mikhayl F. Budyka 《International journal of quantum chemistry》2012,112(14):2643-2649
Potential energy surface (PES) for 1‐styrylnaphthalene was calculated by PM3 method for the S0 state and PM3‐CI(2x2) method with configuration interaction for the S1 state. Scanning PES along both isomerization and cyclization reaction coordinates enabled to reveal the minimum energy path (MEP) with low barriers on the S1 PES from E‐isomer to dihydrocyclophotoproduct (DHP). This is consistent with formation of the photocyclization product in one‐photon process during irradiation of E‐isomer. Additionally, the MEP was found to bypass the coordinate region of Z‐isomer, i.e. one‐photon E‐isomer‐to‐DHP photocyclization does not demand participation of the excited Z‐isomer. Therefore, adiabatic trans‐to‐cis isomerization is likely not an intermediate stage on the E‐isomer photocyclization pathway, and experimentally observed one‐photon formation of the DHP from the E‐isomer is likely not an evidence for adiabatic trans‐to‐cis photoisomerization, as it is usually assumed. According to the results obtained, two photochemical reactions of E‐isomer, photoisomerization to Z‐isomer and photocyclization to DHP, are not consecutive but parallel reactions with branching at perpendicular conformer on the S1 PES. © 2012 Wiley Periodicals, Inc. 相似文献
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Achim Günther 《Nachrichten aus der Chemie》2003,51(12):1284-1284
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2‐X‐1,3,2‐diazaarsolenes and 2‐X‐1,3,2‐ stibolenes (X = Cl, Br) were prepared from appropriate α‐amino‐aldimine precursors via transamination with ClSb(NMe2)2 or via base‐induced dehydrohalogenation with EX3 (E = As, Sb). The products were further converted into 2‐iodo‐derivatives via halide exchange with Me3SiI, or into 1,3,2‐diazaarsolenium or 1,3,2‐stibolenium salts via halide abstraction using E′X3 (E′ = Al, Ga, Sb) or Me3SiOTf. All compounds synthesized were characterized by spectroscopic data and several of them by single‐crystal X‐ray diffraction studies. The results of these investigations confirmed that diazaarsolenium or stibolenium cations are stabilized by similar π‐delocalization effects as the corresponding diazaphospholenium cations. 2‐Halogeno‐1,3,2‐diazaarsolenes and 2‐halogeno‐132‐stibolenes are best addressed as molecular species whose covalent E X bonds are as in 2‐chloro‐diazaphospholenes weakened by intramolecular π(C2N2) → σ*(E X) and, in the case of the Sb‐containing heterocycles, inter‐ molecular n(X′) → σ*(E X) hyperconjugation between the σ* (E X) orbital and a lone‐pair of electrons on the halogen atom of a neighboring molecule. Correlation of structural and spectroscopic data and the evaluation of halide transfer reactions allowed to conclude that the extent of E X bond weakening in the 2‐X‐substituted heterocycles decreases and thus the Lewis acidity of the cations increases, with increasing atomic number of the pnicogen atom. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:327–338, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20098 相似文献
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Upconverting‐Nanoparticle‐Assisted Photochemistry Induced by Low‐Intensity Near‐Infrared Light: How Low Can We Go?
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Zhijun Chen Wen Sun Prof. Dr. Hans‐Jürgen Butt Dr. Si Wu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(25):9165-9170
Upconverting nanoparticles (UCNPs) convert near‐infrared (NIR) light into UV or visible light that can trigger photoreactions of photosensitive compounds. In this paper, we demonstrate how to reduce the intensity of NIR light for UCNP‐assisted photochemistry. We synthesized two types of UCNPs with different emission bands and five photosensitive compounds with different absorption bands. A λ=974 nm laser was used to induce photoreactions in all of the investigated photosensitive compounds in the presence of the UCNPs. The excitation thresholds of the photoreactions induced by λ=974 nm light were measured. The lowest threshold was 0.5 W cm?2, which is lower than the maximum permissible exposure of skin (0.726 W cm?2). We demonstrate that low‐intensity NIR light can induce photoreactions after passing through a piece of tissue without damaging the tissue. Our results indicate that the threshold for UCNP‐ assisted photochemistry can be reduced by using highly photosensitive compounds that absorb upconverted visible light. Low excitation intensity in UCNP‐assisted photochemistry is important for biomedical applications because it minimizes the overheating problems of NIR light and causes less photodamage to biomaterials. 相似文献
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Jimin Xu Guolin Cheng Deyong Su Yantao Liu Xinyan Wang Yuefei Hu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(47):13105-13110
A novel palladium catalyzed direct ortho‐arylation of N‐phenacylpyridinium bromide was developed. The amazing N‐phenacyl group regioselectively activates the C? H bond of pyridine and automatically departs from the arylated products. A kinetic isotope effect study proved that the reaction went through a C? H‐bond activation pathway and 2,6‐diphenylpyridine was produced stepwise from 2‐phenylpyridine. 相似文献