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351.
Pyrroles represent building blocks of conjugated poly(heterocycles) which, as organic conductors, are potential materials for organic electronics. Oxidation of β-substituted pyrroles constitutes an important first step in the process of electropolymerization. Ionization energy and the electron spin density distribution are two the most important properties regarding monomers. These properties are studied as a function of electron-withdrawing and electron-donating substituents of pyrrole ring. Evolution of molecular structure, nature of bonding, and electronic density are studied as an effect of ionization process. 相似文献
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Unexpected reactivity of pyridinium salts toward alkynyl Fischer complexes to produce oxo‐heterocycles 下载免费PDF全文
María Inés Flores‐Conde Fabiola N. de la Cruz Julio López J. Óscar C. Jiménez‐Halla Eduardo Peña‐Cabrera Marcos Flores‐Álamo Francisco Delgado Miguel A. Vázquez 《应用有机金属化学》2018,32(3)
The unprecedented reaction of ketone‐containing aromatic pyridinium salts 3a ‐ e and alkynyl Fischer complexes 1a ‐ f proceeds via a mild domino process to provide 4,6‐disubstituted pyran‐2‐ones 5a ‐ k and 2,3,5‐trisubstituted furans 6a ‐ h (45‐97%). According of the results of isotopic labeling experiments, a mechanism involving an initial Michael addition appears to be the key step, obtaining a mesomeric structure responsible for the formation of both products. 相似文献
356.
Intrinsic self‐initiating thermal ring‐opening polymerization of 1,3‐benzoxazines without the influence of impurities using very high purity crystals 下载免费PDF全文
Lu Han María Laura Salum Kan Zhang Pablo Froimowicz Hatsuo Ishida 《Journal of polymer science. Part A, Polymer chemistry》2017,55(20):3434-3445
A phenol/aniline type monofunctional benzoxazine monomer, PH‐a , is synthesized and highly purified to study the intrinsic thermal ring‐opening polymerization of benzoxazines without the influence of any impurity. The successful synthesis of the monomer and its corresponding chemical structure are confirmed by Fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance (1H NMR) spectroscopy. Purity of the compound is evaluated through differential scanning calorimetry (DSC) as well as elemental analysis (EA). Moreover, the thermal behavior of benzoxazine monomer toward polymerization is also studied by DSC, indicating that the highly purified benzoxazine monomer actually polymerize upon heating. The results present evidence of an intrinsic tendency for 1,3‐benzoxazines to undergo thermally induced ring‐opening polymerization upon heating only without any impurity participating during the reaction. This reveals that polybenzoxazines can be obtained by both the traditional thermally accelerated (or activated) polymerization, where impurities or purposefully added initiators are involved in the reaction; or, by the classic thermal polymerization, where only heat is enough to initiate the reaction. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3434–3445 相似文献
357.
Viviana Heguaburu Hugo do Carmo Florencia Parpal María Eugenia Amorós Andrés González 《Tetrahedron letters》2017,58(18):1738-1741
The synthesis of 3-hydroxy-2-hexanone and 2,3-hexanediol, two components of the aggregation pheromone of several cerambycid species, is disclosed in here. Starting from 2-hexanone, through an α-hydroxylation using (diacetoxyiodo)benzene, 3-hydroxy-2-hexanone is obtained in good yield. Further reduction of this compound, gives 2,3-hexanediol in excellent yield. A study of the α-hydroxylation reaction of several alkylketones using an hypervalent iodine reagent is also disclosed in here. The synthesis of optically active compounds (R)- and (S)-3-hydroxy-2-hexanone was achieved starting from 2-hexanone with nitrosobenzene and l- and d-proline respectively, in several reaction media. 相似文献
358.
Víctor G. Alfaro-García Anna M. Gil-Lafuente Gerardo G. Alfaro Calderón 《Computational & Mathematical Organization Theory》2017,23(3):391-408
In recent years, a trend for accelerating the economic, social and environmental development of cities through associations, organization and creation of synergies has been identified. Our investigation applies a grouping model in order to identify municipalities that could create optimal synergies towards the construction of competitive advantages. In order to achieve this task, we use tools of Fuzzy Logic to evaluate subjective and qualitative characteristic elements of different municipalities under Galois’ group theory. Results conclude on 32 different groups ordered in 7 different levels, relating 12 municipalities of a specific region according to 8 competitive variables. This work seeks to shed light in the conformation of groups under uncertain conditions and the deep examination of the characteristic competitive elements in a specific region for further policy and decision-making processes. 相似文献
359.
Bala Karlo Brcanov Dejan Gvozdenović Nebojša 《Central European Journal of Operations Research》2017,25(3):525-543
Central European Journal of Operations Research - In this paper we study a problem that arose while planning the delivery of perishable goods, such as newspapers or foodstuff, in urban areas. The... 相似文献
360.