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11.
Intermolecular and Regioselective Access to Polysubstituted Benzo‐ and Dihydrobenzo[c]azepine Derivatives: Modulating the Reactivity of Group 6 Non‐Heteroatom‐Stabilized Alkynyl Carbene Complexes
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Jairo González Dr. Aránzazu Gómez Ignacio Funes‐Ardoiz Dr. Javier Santamaría Diego Sampedro 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(23):7061-7068
We highlight the versatility of non‐heteroatom‐stabilized tungsten–carbene complexes 3 synthesized in situ, which have been used in a modular approach to access 2‐benzazepinium isolable intermediates 5 . By employing very mild conditions, benzazepinium derivatives 5 have been obtained in high yield from simple compounds, such as acetylides 2 , Fischer‐type alkoxycarbenes 1 , and phenylimines 4 . The process, involving a formal [4+3] heterocycloaddition, occurs in a totally regioselective manner, which differs from the approach previously observed in similar procedures for other carbene analogues. This work, which involves three components, reveals a control of the reactivity of non‐heteroatom‐stabilized carbene complexes 3 ([4+3] vs. [2+2]‐heterocycloaddition reactions) depending on the acetylide substitution pattern. The influence of the substitution pattern in the behavior of the complexes has been computationally analyzed and rationalized. Finally, elaboration of the 2‐benzazepinium intermediates allows access to 3H‐benzo[c]azepines 6 and 3H‐1,2‐dihydrobenzo[c]azepines 7 – 9 with high control of the substitution of the nine positions of the heterocycle. 相似文献
12.
Bixue Xu Luca Unione Dr. Joao Sardinha Shaoping Wu Prof. Mélanie Ethève‐Quelquejeu Prof. Amelia Pilar Rauter Prof. Yves Blériot Dr. Yongmin Zhang Dr. Sonsoles Martín‐Santamaría Dr. Dolores Díaz Prof. Jesus Jiménez‐Barbero Prof. Matthieu Sollogoub 《Angewandte Chemie (International ed. in English)》2014,53(36):9597-9602
Molecular mimicry is an essential part of the development of drugs and molecular probes. In the chemical glycobiology field, although many glycomimetics have been developed in the past years, it has been considered that many failures in their use are related to the lack of the anomeric effects in these analogues. Additionally, the origin of the anomeric effects is still the subject of virulent scientific debates. Herein, by combining chemical synthesis, NMR methods, and theoretical calculations, we show that it is possible to restore the anomeric effect for an acetal when replacing one of the oxygen atoms by a CF2 group. This result provides key findings in chemical sciences. On the one hand, it strongly suggests the key relevance of the stereoelectronic component of the anomeric effect. On the other hand, the CF2 analogue adopts the natural glycoside conformation, which might provide new avenues for sugar‐based drug design. 相似文献
13.
Darwin P. R. Kint Antxon Martínez De Ilarduya Sebastin Muoz‐Guerra 《Journal of Polymer Science.Polymer Physics》2001,39(13):1553-1564
The microstructure and crystallization behavior of a set of poly(ethylene terephthalate‐co‐5‐nitroisophthalate) copolymers (PETNI) containing 5‐nitroisophthalic units in the 10–50 mol % range were examined and compared to those of poly(ethylene terephthalate) (PET) and poly(ethylene terephthalate‐co‐isophthalate) (PETI) copolymers. A 13C NMR analysis of PETNI copolymers in a trifluoroacetic acid solution indicates that they are random copolymers with average sequence lengths in accordance with ideal polycondensation statistics. Differential scanning calorimetry (DSC) studies show that PETNI containing 5‐nitroisophthalic units up to 20 mol % are able to crystallize and that crystallization takes place in these copolymers at much slower rates than in PET. Wide‐angle X‐ray diffraction from powder and fibers reveals that crystallizable PETNI adopts the same triclinic crystal structure as PET, with the nitroisophthalate units being excluded from crystallites. Fourier transform infrared in combination with cross‐polarization/magic‐angle spinning 13C NMR spectroscopy demonstrates the occurrence of a gauche–trans conversion encompassing the crystallization process. A correlation between DSC and spectroscopic data leads us to conclude that the content of trans conformer in the noncrystallized phase of PETNI is higher than in both PET and PETI copolymers and suggests that secondary crystallization in the homopolymer must proceed by a mechanism different than that in copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1553–1564, 2001 相似文献
14.
15.
Varela M Grogger W Arias D Sefrioui Z León C Ballesteros C Krishnan KM Santamaría J 《Physical review letters》2001,86(22):5156-5159
Charge neutrality and stoichiometry impose severe restrictions on the mechanisms of epitaxial growth of complex oxides. The fundamental question arises of what is the minimum growth unit when sample thickness is reduced beyond the size of the unit cell. We have investigated the growth mechanism of YBa2Cu3O7 cuprate superconductor, using a consistent approach based on the growth of noninteger numbers of YBa2Cu3O7 layers in YBa(2)Cu(3)O(7)/PrBa(2)Cu3O7 superlattices. Ex situ chemical and structural analysis evidence a 2D block-by-block mechanism in which the minimum growth units are complete unit cell blocks, growing coherently over large lateral distances. 相似文献
16.
Robert Quintana Antxon martínez de Ilarduya Abdelilah Alla Sebastián Muñoz‐Guerra 《Journal of polymer science. Part A, Polymer chemistry》2011,49(10):2252-2260
Three series of terephthalate polyesters (copolyesters and terpolyesters) containing 70, 80, and 90 mol % of ethylene glycol respectively, 1,4‐cyclohexanedimethanol (CHDM) and isosorbide in varying ratios, were synthesized by melt polycondensation. It was found that only ~75 mol % of the feeding isosorbide was incorporated in the resulting polyesters and that their content in diethylene glycol oscillated between 2 and 4 mol %. The polyesters had weight‐average molecular weights in the 25,000–33,000 g mol?1 range and polydispersities between 2 and 2.5. The combined 1H and 13C NMR analysis revealed that the microstructure of all these polyesters was at random. They showed good thermal stability with decomposition temperatures above 400 °C. Their glass‐transition temperatures were observed to increase with the content in cyclic diols, this effect being more pronounced when isosorbide was the replacing comonomer. Only the series containing 90 mol % of ethylene terephthalate units was able to crystallize upon cooling from the melt. Compared isothermal crystallizations revealed that isosorbide was more effective than CHDM in repressing the crystallizability of PET. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
17.
Virginia Cebrián Clara Yagüe Manuel Arruebo Francisco M. Martín-Saavedra Jesus Santamaría Nuria Vilaboa 《Journal of nanoparticle research》2011,13(9):4097-4108
Mesoporous silica nanoparticles have been synthesized and functionalized with four different types of molecules containing
amino groups, i.e., with primary amines only, with quaternary amines, with quaternized cyclic amines, or with polyethylenimine
(PEI), which is formed by primary, secondary, and tertiary amines. These nanoparticles were then incubated with reporter plasmids
and the ability of the resulting complexes to transfect human cells was studied. Only nanoparticles functionalized with PEI
were efficient for transfection. The agglomeration behavior and the electrokinetic potential of the nanoparticle–plasmid complexes
have been studied, as well as their cell internalization behavior using a fluorescent-labeled plasmid that allows its monitorization
by confocal microscopy. The results indicate that the efficiency of PEI-functionalized nanoparticles for transfection resides
to some extent in the different characteristics imparted to the nanoparticles regarding agglomeration and surface charge behavior. 相似文献
18.
Diego Adolfo Santamaría Razo Luca Pallavidino Edoardo Garrone Francesco Geobaldo Emiliano Descrovi Angelica Chiodoni Fabrizio Giorgis 《Journal of nanoparticle research》2008,10(7):1225-1229
A sol-gel synthesis procedure based on the method proposed by Stöber et al. (J Colloid Interface Sci 26:302–315, 1968) has been adopted for the one-step preparation of mono-dispersed silica nanospheres. An excellent control of the particle diameter over a wide range is obtained by varying the amount of silicon alkoxide only, while the concentration of all other components is kept fixed: this allows the fabrication of artificial opals with a finely tuned and precisely predictable lattice parameter. 相似文献
19.
Celia Regaño Romina Marín Abdelilah Alla José I. Iribarren Antxon Martínez De Ilarduya Sebastián Muñoz‐Guerra 《Journal of Polymer Science.Polymer Physics》2007,45(1):116-125
The crystal structure and crystallization behavior of a series of poly(ester amide)s derived from L ‐tartaric acid, 1,6‐hexanediamine, and 6‐amino‐1‐hexanol were examined. The study included aregic polymers containing 5, 10, and 20% of ester groups in addition to the syndioregic polymer containing equal amounts of amide and ester groups. X‐ray diffraction data revealed that all the aregic poly(ester amide)s adopt the same crystal structure as the parent polyamide made of L ‐tartaric acid, and 1,6‐hexanediamine. In this structure, chains are slightly compressed and arranged as in the α‐form of nylon 66. Solid‐state nuclear magnetic resonance (NMR) revealed that ester groups are excluded from the crystal phase except for the case of the syndioregic polymer. Isothermal crystallization kinetics was analyzed according to the Avrami theory. Crystallization rates were found to decrease regularly with increasing contents in ester groups and with increasing crystallization temperature. Avrami exponent values close to 2 were found whereas spherulitic morphologies were observed by optical microscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 116–125, 2007 相似文献
20.
The stability and the rheological properties of blends of a 60/70 penetration-grade bitumen with conventional HDPEs and metallocene catalysed LLDPEs (m-LLDPE) are investigated. Considerably better stability results are obtained using m-LLDPEs instead of conventional polyethylenes, allowing one to avoid phase separation of the emulsion-like system during storage at high temperature. Thermodynamical interaction between bitumen and polyethylene is discarded as a cause of the observed difference, because the solubility parameter is practically the same for all the investigated polyethylenes. The result is explained on the basis of the lower melt elasticity of m-LLDPEs (attributed to their narrow molecular weight distribution), which facilitates the drop breakup during mixing process. The modification of bitumen with any of the m-LLDPEs considered in this work gives a new material with considerably improved viscoelastic properties. 相似文献