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91.
Carlos Seoane Jos L. Soto Pilar Zamorano Margarita Quinteiro 《Journal of heterocyclic chemistry》1981,18(2):309-314
Ring transformations of 4H-pyrans into pyridines are reported. Treatment of 2-amino-4,6-diaryl-3,5-dicyano-4H-pyrans (I) with nitrosylsulfuric acid brings about their transformation into 3,5-dicyano-4,6-diaryl-2-pyridones (VI) which can also be obtained from α-benzoylcinnamonitriles (IX) and cyanoacetamide. Similarly, 2-amino-4,6-diaryl-5-carbethoxy-3-cyano-4H-pyrans (II) lead to 4,6-diaryl-5-carbethoxy-3-cyano-2-pyridones (VII). Treatment of both series of pyrans with sulfuric acid results in the formation of the corresponding 3,4-dihydro-2-pyridones (IV and V). Reaction of pyrans II with ammonium acetate in acetic acid yields 2-amino-4,6-diaryl-5-carbethoxy-3-cyanopyridines (XII). Pyrans I undergo an entirely different type of reaction upon treatment with this reagent leading to 2,4,6-triaryl-3,5-dicyano-1,4-dihydropyridines (XV). 相似文献
92.
Fused pyrazolopyrimidines. I. Pyrazolo[4,3-e]-v-triazolo[1,5-a]pyrimidine. A new heterocyclic system
Misbahul Ain Khan Antonio Carlos Carreira Freitas 《Journal of heterocyclic chemistry》1980,17(7):1603-1604
5-Azido-4-cyano-1-phenylpyrazole reacts with benzylcyanide in the presence of sodium methoxide to give the title ring system. 相似文献
93.
Rosenberg Edward Freeman William Carlos Zinnia Hardcastle Kenneth Yong Jin Yoo Milone Luciano Gobetto Roberto 《Journal of Cluster Science》1992,3(4):439-457
The general relationships between trinuclear cluster reactivity and the ligand dynamical processes in these systems are explored. Three specific mechanistic studies are presented: (1) the rate and stereochemistry of ligand addition to 3-imidoyl complexes, (2) the factors influencing the rate of carbon-hydrogen bond activation in 3-alkyne complexes, and (3) the origin of anomalously large kinetic deuterium isotope effect in metal to ligand and ligand to metal hydrogen transfer in trinuclear and binuclear complexes. In all three cases, the current state of the mechanistic studies are summarized and the possible rate of specific ligand dynamical processes in controlling the mechanism are put forth. 相似文献
94.
95.
Karen Beatriz Méndez-Rodríguez Nicté Figueroa-Vega César Arturo Ilizaliturri-Hernandez Mónica Cardona-Alvarado Jaime Antonio Borjas-García Carlos Kornhauser Juan Manuel Malacara Rogelio Flores-Ramírez Francisco Javier Pérez-Vázquez 《Biomedical chromatography : BMC》2020,34(12):e4956
Metabolomics is a potential tool for the discovery of new biomarkers in the early diagnosis of diseases. An ultra-fast gas chromatography system equipped to an electronic nose detector (FGC eNose) was used to identify the metabolomic profile of Volatile Organic Compounds (VOCs) in type 2 diabetes (T2D) urine from Mexican population. A cross-sectional, comparative, and clinical study with translational approach was performed. We recruited twenty T2D patients and twenty-one healthy subjects. Urine samples were taken and analyzed by FGC eNose. Eighty-eight compounds were identified through Kovats's indexes. A natural variation of 30% between the metabolites, expressed by study groups, was observed in Principal Component 1 and 2 with a significant difference (p < 0.001). The model, performed through a Canonical Analysis of Principal coordinated (CAP), allowed a correct classification of 84.6% between healthy and T2D patients, with a 15.4% error. The metabolites 2-propenal, 2-propanol, butane- 2,3-dione and 2-methylpropanal, were increased in patients with T2D, and they were strongly correlated with discrimination between clinically healthy people and T2D patients. This study identified metabolites in urine through FGC eNose that can be used as biomarkers in the identification of T2D patients. However, more studies are needed for its implementation in clinical practice. 相似文献
96.
Cyrille Charpentier Jérémy Salaam Dr. Aline Nonat Fabio Carniato Dr. Olivier Jeannin Dr. Isabel Brandariz Dr. David Esteban-Gomez Dr. Carlos Platas-Iglesias Dr. Loïc J. Charbonnière Prof. Mauro Botta 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(24):5407-5418
The heptadentate ligand L was shown to form an extremely stable Gd complex at neutral pH with a pGd value of 18.4 at pH 7.4. The X-ray crystal structures of the complexes formed with Gd and Tb displayed two very different coordination behaviors being, respectively, octa- and nonacoordinated. The relaxometric properties of the Gd complex were studied by field-dependent relaxivity measurements at various temperatures and by 17O NMR spectroscopy. The pH-dependence of the longitudinal relaxivity profile indicated large changes around neutral pH leading to a very large value of 10.1 mm −1⋅s−1 (60 MHz, 298 K) at pH 4.7. The changes were attributed to an increase of the hydration number from one water molecule in basic conditions to two at acidic pH. A similar trend was observed for the luminescence of the Eu complex, confirming the change in hydration state. DOSY experiments were performed on the Lu analogue, pointing to the absence of dimers in solution in the considered pH range. A breathing mode of the complex was postulated, which was further supported by 1H and 31P NMR spectroscopy of the Yb complex at varying pH and was finally modeled by DFT calculations. 相似文献
97.
Juan Carlos López-López Dr. Delia Bautista Dr. Pablo González-Herrero 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(49):11307-11315
A stereoselective synthetic route to homo- and heteroleptic facial tris-cyclometalated PtIV complexes is reported, involving the oxidative addition of 2-(2-pyridyl)- or 2-(1-isoquinolinyl)benzenediazonium salts to cis-[Pt(C^N)2] precursors, with C^N=cyclometalated 2-(p-tolyl)pyridine (tpy), 2-phenylquinoline (pq), 2-(2-thienyl)pyridine or 1-phenylisoquinoline (piq), to produce labile diazenide intermediates that undergo photochemical or thermal elimination of N2. The method allows the preparation of derivatives bearing cyclometalated ligands of low π–π* transition energies. The new complexes exhibit phosphorescence in fluid solution at room temperature arising from triplet ligand-centered (3LC) excited states, which, in the cases of the heteroleptic derivatives, involve the ligand with the lowest π–π* gap. The heteroleptic piq derivatives exhibit fluorescence and dual phosphorescence from different ligand-centered excited states in rigid media, demonstrating the potential of cyclometalated PtIV complexes as multi-emissive materials. 相似文献
98.
Dr. Carlos Lázaro-Milla Jon Macicior Dr. Hikaru Yanai Prof. Dr. Pedro Almendros 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(41):8983-8989
Herein, we report investigations embodying the first example of reversal of the native regioselectivity in the reaction of allenols with electrophiles. The effortlessness of C−C bond formation, mild reaction conditions, neither catalysts nor light irradiation, and exquisite selectivity, both in terms of functional-group tolerance and chemo-, site-, and stereo-selectivity, converts this trifluorosulfonylation-rearrangement sequence into an appealing protocol for the preparation of novel functionalized enones. The synthetic utility of this method has been validated by the conversion of the initially prepared bis(triflyl)enones into a variety of bis(triflyl)-functionalized molecules such as 1,3-dienes, allylic alcohols, pyrroles, pyrazoles, and chromenes. Besides, DFT calculations have provided a reliable understanding of observed selectivity. 相似文献
99.
Dr. Giovanny Carvalho dos Santos Juan Carlos Roldao Dr. Junqing Shi Dr. Begoña Milián-Medina Prof. Dr. Luiz Carlos da Silva-Filho Dr. Johannes Gierschner 《Chemphyschem》2020,21(16):1797-1804
A combined spectroscopic and TD-DFT case study was performed, to identify a robust method to calculate the complex near UV/Vis absorption spectra of various amino- vs. nitro-substituted 2,4-diphenylquinolines, which vary strongly under neutral and successively acidic conditions. For this, different DFT functionals were tested for geometry optimization and the TD part to calculate the neutral and different protonated species in a fast screening approach, i. e. using single point calculations in an implicit solvent. Offset-corrected M06HF, hitherto only applied to polymers, was identified as a suitable method to reproduce the absorption spectra in a reasonable fashion for all different substitution pattern and all different protonated species at different pH values; moreover, the method properly predicts the energetic ordering of low-lying n-π* and ππ* transitions, which is decisive for the non-/emissive nature of the different compounds. In all, this might provide a valuable tool for computer-aided design of related classes of compounds. 相似文献
100.
Eduardo CortS Corts Carlos M. Alcocer Castrejn 《Journal of heterocyclic chemistry》1997,34(6):1809-1812
A series of twelve new 2,3-dihydro-4-(para-substituted-phenyl)-7-[(o-, m-, and p-substituted)phenoxy]-1H-1,5-benzodiazepine-2-thiones, which have potentially useful pharmacological properties, has been synthesized by condensing the 3,3-dimercapto-1-(para-substituted phenyl)-2-propen-1-one with 3,4-diaminophenyl-R-phenyl ethers. The structure of all products was corroborated by ir, 1H-nmr, 13C-nmr and ms. 相似文献