排序方式: 共有7条查询结果,搜索用时 15 毫秒
1
1.
Palomo C Oiarbide M Landa A Esnal A Linden A 《The Journal of organic chemistry》2001,66(12):4180-4186
A concise access to alpha,beta-dihydroxy alpha-amino acid-derived N-carboxy anhydrides (NCAs) with either like or unlike relative configuration is described. The key steps of the synthetic route are the preparation of the nonracemic 4-alkenyl beta-lactams, through either Horner-type olefination of a common 4-formyl beta-lactam or the Corey-Winter alkene synthesis applied to 4-dihydroxyalkyl beta-lactams, followed by the Sharpless AD reaction, and a subsequent ring expansion of the corresponding 4-substituted 3-hydroxy beta-lactams promoted by TEMPO. The opening of thus-prepared NCAs upon treatment with different O- and N-nucleophiles, including alpha-amino esters which lead to peptides, has also been studied under various reaction conditions. 相似文献
2.
Ixone Esnal Arlette Urías‐Benavides Dr. C. F. Azael Gómez‐Durán Dr. Carlos A. Osorio‐Martínez Prof. Inmaculada García‐Moreno Prof. Angel Costela Dr. Jorge Bañuelos Nerea Epelde Prof. Iñigo López Arbeloa Dr. Rongrong Hu Prof. Ben Zhong Tang Prof. Eduardo Peña‐Cabrera 《化学:亚洲杂志》2013,8(11):2691-2700
A thorough study of the photophysical and laser properties of 8‐aminoboron dipyrromethene dyes was undertaken to determine the role of amine substitution and spatial disposition on the properties of the dyes. It was found that the fluorescent and laser response varied significantly. Although primary amines give rise to highly fluorescent products at the blue edge of the visible region, secondary amines yield nonfluorescent analogues in polar media. The crystal structures of two analogues are reported and described. Steric hindrance and the higher electron‐releasing ability of the amine favor the formation of a quenching intramolecular charge‐transfer state. Accordingly, boron dipyrromethene derivatives with primary amines exhibited laser emission with efficiencies of up to 44 %. Besides, the more efficient derivative was also the most photostable, leading to a significant improvement in the lasing performance with regard to previously reported 8‐aminoboron dipyrromethene derivatives. An increase in the solvent polarity, and mainly the presence of tertiary cyclic amines, led to a dramatic decrease or even the loss of the laser action. 相似文献
3.
First Highly Efficient and Photostable E and C Derivatives of 4,4‐Difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) as Dye Lasers in the Liquid Phase,Thin Films,and Solid‐State Rods 下载免费PDF全文
Gonzalo Duran‐Sampedro Ixone Esnal Prof. Antonia R. Agarrabeitia Dr. Jorge Bañuelos Prieto Dr. Luis Cerdán Prof. Inmaculada García‐Moreno Prof. Angel Costela Prof. Iñigo Lopez‐Arbeloa Prof. María J. Ortiz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(9):2646-2653
A new library of E‐ and C‐4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) derivatives has been synthesized through a straightforward protocol from commercially available BODIPY complexes, and a systematic study of the photophysical properties and laser behavior related to the electronic properties of the B‐substituent group (alkynyl, cyano, vinyl, aryl, and alkyl) has been carried out. The replacement of fluorine atoms by electron‐withdrawing groups enhances the fluorescence response of the dye, whereas electron‐donor groups diminish the fluorescence efficiency. As a consequence, these compounds exhibit enhanced laser action with respect to their parent dyes, both in liquid solution and in the solid phase, with lasing efficiencies under transversal pumping up to 73 % in liquid solution and 53 % in a solid matrix. The new dyes also showed enhanced photostability. In a solid matrix, the derivative of commercial dye PM597 that incorporated cyano groups at the boron center exhibited a very high lasing stability, with the laser emission remaining at the initial level after 100 000 pump pulses in the same position of the sample at a 10 Hz repetition rate. Distributed feedback laser emission was demonstrated with organic films that incorporated parent dye PM597 and its cyano derivative. The films were deposited onto quartz substrates engraved with appropriate periodical structures. The C derivative exhibited a laser threshold lower than that of the parent dye as well as lasing intensities up to three orders of magnitude higher. 相似文献
4.
Osorio-Martínez CA Urías-Benavides A Gómez-Durán CF Bañuelos J Esnal I López Arbeloa I Peña-Cabrera E 《The Journal of organic chemistry》2012,77(12):5434-5438
The role of the amino group twisting ability in the BODIPY photophysics for nonsterically hindered and constrained molecular structures was studied. When a coplanar disposition of the amino and the BODIPY core is feasible, a hemicyanine-like delocalized π-system gives rise to novel blue and efficient BODIPY laser dyes. The key role of such rotamer is confirmed by newly synthesized derivatives where the amino and the BODIPY core are electronically decoupled by steric repulsions. 相似文献
5.
Dr. Cesar F. A. Gómez‐Durán Ixone Esnal Dr. Ismael Valois‐Escamilla Arlette Urías‐Benavides Dr. Jorge Bañuelos Prof. Iñigo López Arbeloa Dr. Inmaculada García‐Moreno Prof. Eduardo Peña‐Cabrera 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(3):1048-1061
Herein, we report the synthesis of polyfunctional BODIPY building blocks suitable to be subjected to several reaction sequences with complete chemoselectivity, thereby allowing the preparation of complex BODIPY derivatives in a versatile and programmable manner. The reactions included the Liebeskind–Srogl cross‐coupling reaction (LSCC), nucleophilic aromatic substitution (SNAr), Suzuki, Sonogashira, and Stille couplings, and a desulfitative reduction of the MeS group. This novel synthetic protocol is a powerful route to design a library of compounds with tailored photophysical properties for advanced applications. In this context, it is noteworthy that it offers a straightforward and cost‐effective strategy to shift the BODIPY emission deep into the near‐infrared spectral region while retaining high fluorescence quantum yields as well as highly efficient and stable laser action. These new dyes outperform the lasing behaviour of dyes considered as benchmarks over the red spectral region, overcoming the important drawbacks associated with these commercial laser dyes, namely low absorption at the standard pump wavelengths (355 and 532 nm) and/or poor photostability. 相似文献
6.
Effect of the glottal source and the vocal tract on the partials amplitude of vibrato in male voices
In this paper the production of vocal vibrato is investigated. The most relevant features of the acoustical vibrato signal, frequency and amplitude variations of the partials, will be related to the voice production features, glottal source (GS) and vocal tract response (VTR). Unlike previous related works, in this approach, the effect on the amplitude variations of the partials of each one of the above-mentioned voice production features will be identified in recordings of natural singing voice. Moreover, we will take special care of the reliability of the measurements, and, to this aim, a noninteractive vibrato production model will be also proposed in order to describe the vibrato production process and, more importantly, validate the measurements carried out in natural vibrato. Based on this study, it will be shown that during a few vibrato cycles, the glottal pulse characteristics, as well as the VTR, do not significantly change, and only the fundamental frequency of the GS varies. As a result, the pitch variations can be attributed to the GS, and these variations, along with the vocal tract filtering effect, will result in frequency and amplitude variations of the acoustic signal partials. 相似文献
7.
Ixone Esnal Dr. Ismael Valois‐Escamilla César F. A. Gómez‐Durán Arlette Urías‐Benavides María L. Betancourt‐Mendiola Prof. Iñigo López‐Arbeloa Dr. Jorge Bañuelos Prof. Inmaculada García‐Moreno Prof. Angel Costela Prof. Eduardo Peña‐Cabrera 《Chemphyschem》2013,14(18):4134-4142
A series of meso‐substituted boron‐bipyrromethene (BODIPY) dyes are synthesized and their laser and photophysical properties systematically studied. Laser emission covering a wide visible spectral region (from blue to orange) is obtained by just changing the electron donor character of the heteroatom at position 8. The additional presence of methyl groups at positions 3 and 5 results in dyes with a photostability similar to that of the unsubstituted dye but with much improved efficiency. Correlation of the lasing properties of the different dyes to their photophysical properties provides inklings to define synthetic strategies of new BODIPY dyes with enhanced efficiency and modulated wavelength emission over the visible spectral region. 相似文献
1